Add support for module imports

crates/nu-engine/src/eval.rs

@@ -156,10 +156,10 @@ pub fn eval_expression(
         Expr::Var(var_id) => context
             .get_var(*var_id)
             .map_err(move |_| ShellError::VariableNotFoundAtRuntime(expr.span)),
-        Expr::FullCellPath(column_path) => {
+        Expr::FullCellPath(cell_path) => {
-            let value = eval_expression(context, &column_path.head)?;
+            let value = eval_expression(context, &cell_path.head)?;
 
-            value.follow_cell_path(&column_path.tail)
+            value.follow_cell_path(&cell_path.tail)
         }
         Expr::RowCondition(_, expr) => eval_expression(context, expr),
         Expr::Call(call) => eval_call(context, call, Value::nothing()),

crates/nu-parser/src/errors.rs

@@ -151,4 +151,12 @@ pub enum ParseError {
     #[error("{0}")]
     #[diagnostic(code(nu::parser::assignment_mismatch), url(docsrs))]
     AssignmentMismatch(String, String, #[label("{1}")] Span),
+
+    #[error("Missing import pattern.")]
+    #[diagnostic(code(nu::parser::missing_import_pattern), url(docsrs))]
+    MissingImportPattern(#[label = "needs an import pattern"] Span),
+
+    #[error("Module export not found.")]
+    #[diagnostic(code(nu::parser::export_not_found), url(docsrs))]
+    ExportNotFound(#[label = "could not find imports"] Span),
 }

crates/nu-parser/src/flatten.rs

@@ -79,10 +79,10 @@ pub fn flatten_expression(
         Expr::Float(_) => {
             vec![(expr.span, FlatShape::Float)]
         }
-        Expr::FullCellPath(column_path) => {
+        Expr::FullCellPath(cell_path) => {
             let mut output = vec![];
-            output.extend(flatten_expression(working_set, &column_path.head));
+            output.extend(flatten_expression(working_set, &cell_path.head));
-            for path_element in &column_path.tail {
+            for path_element in &cell_path.tail {
                 match path_element {
                     PathMember::String { span, .. } => output.push((*span, FlatShape::String)),
                     PathMember::Int { span, .. } => output.push((*span, FlatShape::Int)),

crates/nu-parser/src/lib.rs

@@ -2,6 +2,7 @@ mod errors;
 mod flatten;
 mod lex;
 mod lite_parse;
+mod parse_keywords;
 mod parser;
 mod type_check;
 
@@ -9,4 +10,7 @@ pub use errors::ParseError;
 pub use flatten::{flatten_block, FlatShape};
 pub use lex::{lex, Token, TokenContents};
 pub use lite_parse::{lite_parse, LiteBlock};
+pub use parse_keywords::{
+    parse_alias, parse_def, parse_def_predecl, parse_let, parse_module, parse_use,
+};
 pub use parser::{parse, Import, VarDecl};

crates/nu-parser/src/parse_keywords.rs

@@ -0,0 +1,484 @@
+use nu_protocol::{
+    ast::{Block, Call, Expr, Expression, ImportPatternMember, Pipeline, Statement},
+    engine::StateWorkingSet,
+    span, DeclId, Span, SyntaxShape, Type,
+};
+
+use crate::{
+    lex, lite_parse,
+    parser::{
+        check_name, garbage, garbage_statement, parse_block_expression, parse_import_pattern,
+        parse_internal_call, parse_signature, parse_string,
+    },
+    ParseError,
+};
+
+pub fn parse_def_predecl(working_set: &mut StateWorkingSet, spans: &[Span]) {
+    let name = working_set.get_span_contents(spans[0]);
+
+    if name == b"def" && spans.len() >= 4 {
+        let (name_expr, ..) = parse_string(working_set, spans[1]);
+        let name = name_expr.as_string();
+
+        working_set.enter_scope();
+        // FIXME: because parse_signature will update the scope with the variables it sees
+        // we end up parsing the signature twice per def. The first time is during the predecl
+        // so that we can see the types that are part of the signature, which we need for parsing.
+        // The second time is when we actually parse the body itworking_set.
+        // We can't reuse the first time because the variables that are created during parse_signature
+        // are lost when we exit the scope below.
+        let (sig, ..) = parse_signature(working_set, spans[2]);
+        let signature = sig.as_signature();
+        working_set.exit_scope();
+
+        if let (Some(name), Some(mut signature)) = (name, signature) {
+            signature.name = name;
+            let decl = signature.predeclare();
+
+            working_set.add_decl(decl);
+        }
+    }
+}
+
+pub fn parse_def(
+    working_set: &mut StateWorkingSet,
+    spans: &[Span],
+) -> (Statement, Option<ParseError>) {
+    let mut error = None;
+    let name = working_set.get_span_contents(spans[0]);
+
+    if name == b"def" && spans.len() >= 4 {
+        //FIXME: don't use expect here
+        let (name_expr, err) = parse_string(working_set, spans[1]);
+        error = error.or(err);
+
+        working_set.enter_scope();
+        let (sig, err) = parse_signature(working_set, spans[2]);
+        error = error.or(err);
+
+        let (block, err) =
+            parse_block_expression(working_set, &SyntaxShape::Block(Some(vec![])), spans[3]);
+        error = error.or(err);
+        working_set.exit_scope();
+
+        if error.is_some() {
+            return (
+                Statement::Pipeline(Pipeline::from_vec(vec![garbage(span(spans))])),
+                error,
+            );
+        }
+
+        let name = name_expr.as_string();
+
+        let signature = sig.as_signature();
+
+        let block_id = block.as_block();
+
+        match (name, signature, block_id) {
+            (Some(name), Some(mut signature), Some(block_id)) => {
+                let decl_id = working_set
+                    .find_decl(name.as_bytes())
+                    .expect("internal error: predeclaration failed to add definition");
+
+                let declaration = working_set.get_decl_mut(decl_id);
+
+                signature.name = name;
+
+                *declaration = signature.into_block_command(block_id);
+
+                let def_decl_id = working_set
+                    .find_decl(b"def")
+                    .expect("internal error: missing def command");
+
+                let call = Box::new(Call {
+                    head: spans[0],
+                    decl_id: def_decl_id,
+                    positional: vec![name_expr, sig, block],
+                    named: vec![],
+                });
+
+                (
+                    Statement::Pipeline(Pipeline::from_vec(vec![Expression {
+                        expr: Expr::Call(call),
+                        span: span(spans),
+                        ty: Type::Unknown,
+                        custom_completion: None,
+                    }])),
+                    error,
+                )
+            }
+            _ => (
+                Statement::Pipeline(Pipeline::from_vec(vec![garbage(span(spans))])),
+                error,
+            ),
+        }
+    } else {
+        (
+            garbage_statement(spans),
+            Some(ParseError::UnknownState(
+                "Expected structure: def <name> [] {}".into(),
+                span(spans),
+            )),
+        )
+    }
+}
+
+pub fn parse_alias(
+    working_set: &mut StateWorkingSet,
+    spans: &[Span],
+) -> (Statement, Option<ParseError>) {
+    let name = working_set.get_span_contents(spans[0]);
+
+    if name == b"alias" {
+        if let Some((span, err)) = check_name(working_set, spans) {
+            return (
+                Statement::Pipeline(Pipeline::from_vec(vec![garbage(*span)])),
+                Some(err),
+            );
+        }
+
+        if let Some(decl_id) = working_set.find_decl(b"alias") {
+            let (call, call_span, _) =
+                parse_internal_call(working_set, spans[0], &spans[1..], decl_id);
+
+            if spans.len() >= 4 {
+                let alias_name = working_set.get_span_contents(spans[1]);
+
+                let alias_name = if alias_name.starts_with(b"\"")
+                    && alias_name.ends_with(b"\"")
+                    && alias_name.len() > 1
+                {
+                    alias_name[1..(alias_name.len() - 1)].to_vec()
+                } else {
+                    alias_name.to_vec()
+                };
+                let _equals = working_set.get_span_contents(spans[2]);
+
+                let replacement = spans[3..].to_vec();
+
+                //println!("{:?} {:?}", alias_name, replacement);
+
+                working_set.add_alias(alias_name, replacement);
+            }
+
+            return (
+                Statement::Pipeline(Pipeline::from_vec(vec![Expression {
+                    expr: Expr::Call(call),
+                    span: call_span,
+                    ty: Type::Unknown,
+                    custom_completion: None,
+                }])),
+                None,
+            );
+        }
+    }
+
+    (
+        garbage_statement(spans),
+        Some(ParseError::UnknownState(
+            "internal error: alias statement unparseable".into(),
+            span(spans),
+        )),
+    )
+}
+
+pub fn parse_module(
+    working_set: &mut StateWorkingSet,
+    spans: &[Span],
+) -> (Statement, Option<ParseError>) {
+    // TODO: Currently, module is closing over its parent scope (i.e., defs in the parent scope are
+    // visible and usable in this module's scope). We might want to disable that. How?
+
+    let mut error = None;
+    let bytes = working_set.get_span_contents(spans[0]);
+
+    // parse_def() equivalent
+    if bytes == b"module" && spans.len() >= 3 {
+        let (module_name_expr, err) = parse_string(working_set, spans[1]);
+        error = error.or(err);
+
+        let module_name = module_name_expr
+            .as_string()
+            .expect("internal error: module name is not a string");
+
+        // parse_block_expression() equivalent
+        let block_span = spans[2];
+        let block_bytes = working_set.get_span_contents(block_span);
+        let mut start = block_span.start;
+        let mut end = block_span.end;
+
+        if block_bytes.starts_with(b"{") {
+            start += 1;
+        } else {
+            return (
+                garbage_statement(spans),
+                Some(ParseError::Expected("block".into(), block_span)),
+            );
+        }
+
+        if block_bytes.ends_with(b"}") {
+            end -= 1;
+        } else {
+            error = error.or_else(|| {
+                Some(ParseError::Unclosed(
+                    "}".into(),
+                    Span {
+                        start: end,
+                        end: end + 1,
+                    },
+                ))
+            });
+        }
+
+        let block_span = Span { start, end };
+
+        let source = working_set.get_span_contents(block_span);
+
+        let (output, err) = lex(source, start, &[], &[]);
+        error = error.or(err);
+
+        working_set.enter_scope();
+
+        // Do we need block parameters?
+
+        let (output, err) = lite_parse(&output);
+        error = error.or(err);
+
+        // We probably don't need $it
+
+        // we're doing parse_block() equivalent
+        // let (mut output, err) = parse_block(working_set, &output, false);
+
+        for pipeline in &output.block {
+            if pipeline.commands.len() == 1 {
+                parse_def_predecl(working_set, &pipeline.commands[0].parts);
+            }
+        }
+
+        let mut exports: Vec<(Vec<u8>, DeclId)> = vec![];
+
+        let block: Block = output
+            .block
+            .iter()
+            .map(|pipeline| {
+                if pipeline.commands.len() == 1 {
+                    // this one here is doing parse_statement() equivalent
+                    // let (stmt, err) = parse_statement(working_set, &pipeline.commands[0].parts);
+                    let name = working_set.get_span_contents(pipeline.commands[0].parts[0]);
+
+                    let (stmt, err) = match name {
+                        // TODO: Here we can add other stuff that's alowed for modules
+                        b"def" => {
+                            let (stmt, err) = parse_def(working_set, &pipeline.commands[0].parts);
+
+                            if err.is_none() {
+                                let decl_name =
+                                    working_set.get_span_contents(pipeline.commands[0].parts[1]);
+
+                                let decl_id = working_set
+                                    .find_decl(decl_name)
+                                    .expect("internal error: failed to find added declaration");
+
+                                // TODO: Later, we want to put this behind 'export'
+                                exports.push((decl_name.into(), decl_id));
+                            }
+
+                            (stmt, err)
+                        }
+                        _ => (
+                            garbage_statement(&pipeline.commands[0].parts),
+                            Some(ParseError::Expected("def".into(), block_span)),
+                        ),
+                    };
+
+                    if error.is_none() {
+                        error = err;
+                    }
+
+                    stmt
+                } else {
+                    error = Some(ParseError::Expected("not a pipeline".into(), block_span));
+                    garbage_statement(spans)
+                }
+            })
+            .into();
+
+        let block = block.with_exports(exports);
+
+        working_set.exit_scope();
+
+        let block_id = working_set.add_module(&module_name, block);
+
+        let block_expr = Expression {
+            expr: Expr::Block(block_id),
+            span: block_span,
+            ty: Type::Block,
+            custom_completion: None,
+        };
+
+        let module_decl_id = working_set
+            .find_decl(b"module")
+            .expect("internal error: missing module command");
+
+        let call = Box::new(Call {
+            head: spans[0],
+            decl_id: module_decl_id,
+            positional: vec![module_name_expr, block_expr],
+            named: vec![],
+        });
+
+        (
+            Statement::Pipeline(Pipeline::from_vec(vec![Expression {
+                expr: Expr::Call(call),
+                span: span(spans),
+                ty: Type::Unknown,
+                custom_completion: None,
+            }])),
+            error,
+        )
+    } else {
+        (
+            garbage_statement(spans),
+            Some(ParseError::UnknownState(
+                "Expected structure: module <name> {}".into(),
+                span(spans),
+            )),
+        )
+    }
+}
+
+pub fn parse_use(
+    working_set: &mut StateWorkingSet,
+    spans: &[Span],
+) -> (Statement, Option<ParseError>) {
+    let mut error = None;
+    let bytes = working_set.get_span_contents(spans[0]);
+
+    // TODO: Currently, this directly imports the module's definitions into the current scope.
+    // Later, we want to put them behind the module's name and add selective importing
+    if bytes == b"use" && spans.len() >= 2 {
+        let (module_name_expr, err) = parse_string(working_set, spans[1]);
+        error = error.or(err);
+
+        let (import_pattern, err) = parse_import_pattern(working_set, spans[1]);
+        error = error.or(err);
+
+        let exports = if let Some(block_id) = working_set.find_module(&import_pattern.head) {
+            // TODO: Since we don't use the Block at all, we might just as well create a separate
+            // Module that holds only the exports, without having Blocks in the way.
+            working_set.get_block(block_id).exports.clone()
+        } else {
+            return (
+                garbage_statement(spans),
+                Some(ParseError::ModuleNotFound(spans[1])),
+            );
+        };
+
+        let exports = if import_pattern.members.is_empty() {
+            exports
+                .into_iter()
+                .map(|(name, id)| {
+                    let mut new_name = import_pattern.head.to_vec();
+                    new_name.push(b'.');
+                    new_name.extend(&name);
+                    (new_name, id)
+                })
+                .collect()
+        } else {
+            match &import_pattern.members[0] {
+                ImportPatternMember::Glob { .. } => exports,
+                ImportPatternMember::Name { name, span } => {
+                    let new_exports: Vec<(Vec<u8>, usize)> =
+                        exports.into_iter().filter(|x| &x.0 == name).collect();
+
+                    if new_exports.is_empty() {
+                        error = error.or(Some(ParseError::ExportNotFound(*span)))
+                    }
+
+                    new_exports
+                }
+            }
+        };
+
+        // Extend the current scope with the module's exports
+        working_set.activate_overlay(exports);
+
+        // Create the Use command call
+        let use_decl_id = working_set
+            .find_decl(b"use")
+            .expect("internal error: missing use command");
+
+        let call = Box::new(Call {
+            head: spans[0],
+            decl_id: use_decl_id,
+            positional: vec![module_name_expr],
+            named: vec![],
+        });
+
+        (
+            Statement::Pipeline(Pipeline::from_vec(vec![Expression {
+                expr: Expr::Call(call),
+                span: span(spans),
+                ty: Type::Unknown,
+                custom_completion: None,
+            }])),
+            error,
+        )
+    } else {
+        (
+            garbage_statement(spans),
+            Some(ParseError::UnknownState(
+                "Expected structure: use <name>".into(),
+                span(spans),
+            )),
+        )
+    }
+}
+
+pub fn parse_let(
+    working_set: &mut StateWorkingSet,
+    spans: &[Span],
+) -> (Statement, Option<ParseError>) {
+    let name = working_set.get_span_contents(spans[0]);
+
+    if name == b"let" {
+        if let Some((span, err)) = check_name(working_set, spans) {
+            return (
+                Statement::Pipeline(Pipeline::from_vec(vec![garbage(*span)])),
+                Some(err),
+            );
+        }
+
+        if let Some(decl_id) = working_set.find_decl(b"let") {
+            let (call, call_span, err) =
+                parse_internal_call(working_set, spans[0], &spans[1..], decl_id);
+
+            // Update the variable to the known type if we can.
+            if err.is_none() {
+                let var_id = call.positional[0]
+                    .as_var()
+                    .expect("internal error: expected variable");
+                let rhs_type = call.positional[1].ty.clone();
+
+                working_set.set_variable_type(var_id, rhs_type);
+            }
+
+            return (
+                Statement::Pipeline(Pipeline::from_vec(vec![Expression {
+                    expr: Expr::Call(call),
+                    span: call_span,
+                    ty: Type::Unknown,
+                    custom_completion: None,
+                }])),
+                err,
+            );
+        }
+    }
+    (
+        garbage_statement(spans),
+        Some(ParseError::UnknownState(
+            "internal error: let statement unparseable".into(),
+            span(spans),
+        )),
+    )
+}

crates/nu-parser/src/parser.rs

@@ -6,11 +6,15 @@ use crate::{
 
 use nu_protocol::{
     ast::{
-        Block, Call, Expr, Expression, FullCellPath, Operator, PathMember, Pipeline,
+        Block, Call, Expr, Expression, FullCellPath, ImportPattern, ImportPatternMember, Operator,
-        RangeInclusion, RangeOperator, Statement,
+        PathMember, Pipeline, RangeInclusion, RangeOperator, Statement,
     },
     engine::StateWorkingSet,
-    span, DeclId, Flag, PositionalArg, Signature, Span, SyntaxShape, Type, VarId,
+    span, Flag, PositionalArg, Signature, Span, SyntaxShape, Type, VarId,
+};
+
+use crate::parse_keywords::{
+    parse_alias, parse_def, parse_def_predecl, parse_let, parse_module, parse_use,
 };
 
 #[derive(Debug, Clone)]
@@ -22,11 +26,11 @@ pub struct VarDecl {
     expression: Expression,
 }
 
-fn garbage(span: Span) -> Expression {
+pub fn garbage(span: Span) -> Expression {
     Expression::garbage(span)
 }
 
-fn garbage_statement(spans: &[Span]) -> Statement {
+pub fn garbage_statement(spans: &[Span]) -> Statement {
     Statement::Pipeline(Pipeline::from_vec(vec![garbage(span(spans))]))
 }
 
@@ -63,7 +67,7 @@ fn check_call(command: Span, sig: &Signature, call: &Call) -> Option<ParseError>
     }
 }
 
-fn check_name<'a>(
+pub fn check_name<'a>(
     working_set: &mut StateWorkingSet,
     spans: &'a [Span],
 ) -> Option<(&'a Span, ParseError)> {
@@ -963,7 +967,7 @@ pub(crate) fn parse_dollar_expr(
     } else if let (expr, None) = parse_range(working_set, span) {
         (expr, None)
     } else {
-        parse_full_column_path(working_set, None, span)
+        parse_full_cell_path(working_set, None, span)
     }
 }
 
@@ -1035,7 +1039,7 @@ pub fn parse_string_interpolation(
                             end: b + 1,
                         };
 
-                        let (expr, err) = parse_full_column_path(working_set, None, span);
+                        let (expr, err) = parse_full_cell_path(working_set, None, span);
                         error = error.or(err);
                         output.push(expr);
                     }
@@ -1071,7 +1075,7 @@ pub fn parse_string_interpolation(
                     end,
                 };
 
-                let (expr, err) = parse_full_column_path(working_set, None, span);
+                let (expr, err) = parse_full_cell_path(working_set, None, span);
                 error = error.or(err);
                 output.push(expr);
             }
@@ -1153,13 +1157,13 @@ pub fn parse_variable_expr(
     }
 }
 
-pub fn parse_full_column_path(
+pub fn parse_full_cell_path(
     working_set: &mut StateWorkingSet,
     implicit_head: Option<VarId>,
     span: Span,
 ) -> (Expression, Option<ParseError>) {
     // FIXME: assume for now a paren expr, but needs more
-    let full_column_span = span;
+    let full_cell_span = span;
     let source = working_set.get_span_contents(span);
     let mut error = None;
 
@@ -1294,7 +1298,7 @@ pub fn parse_full_column_path(
             Expression {
                 expr: Expr::FullCellPath(Box::new(FullCellPath { head, tail })),
                 ty: Type::Unknown,
-                span: full_column_span,
+                span: full_cell_span,
                 custom_completion: None,
             },
             error,
@@ -1371,6 +1375,63 @@ pub fn parse_type(_working_set: &StateWorkingSet, bytes: &[u8]) -> Type {
     }
 }
 
+pub fn parse_import_pattern(
+    working_set: &StateWorkingSet,
+    span: Span,
+) -> (ImportPattern, Option<ParseError>) {
+    let source = working_set.get_span_contents(span);
+    let mut error = None;
+
+    let (tokens, err) = lex(source, span.start, &[], &[b'.']);
+    error = error.or(err);
+
+    if tokens.is_empty() {
+        return (
+            ImportPattern {
+                head: vec![],
+                members: vec![],
+            },
+            Some(ParseError::MissingImportPattern(span)),
+        );
+    }
+
+    let head = working_set.get_span_contents(tokens[0].span).to_vec();
+
+    if let Some(tail) = tokens.get(2) {
+        // FIXME: expand this to handle deeper imports once we support module imports
+        let tail_span = tail.span;
+        let tail = working_set.get_span_contents(tail.span);
+        if tail == b"*" {
+            (
+                ImportPattern {
+                    head,
+                    members: vec![ImportPatternMember::Glob { span: tail_span }],
+                },
+                error,
+            )
+        } else {
+            (
+                ImportPattern {
+                    head,
+                    members: vec![ImportPatternMember::Name {
+                        name: tail.to_vec(),
+                        span: tail_span,
+                    }],
+                },
+                error,
+            )
+        }
+    } else {
+        (
+            ImportPattern {
+                head,
+                members: vec![],
+            },
+            None,
+        )
+    }
+}
+
 pub fn parse_var_with_opt_type(
     working_set: &mut StateWorkingSet,
     spans: &[Span],
@@ -1436,7 +1497,7 @@ pub fn expand_to_cell_path(
     } = expression
     {
         // Re-parse the string as if it were a cell-path
-        let (new_expression, _err) = parse_full_column_path(working_set, Some(var_id), *span);
+        let (new_expression, _err) = parse_full_cell_path(working_set, Some(var_id), *span);
 
         *expression = new_expression;
     }
@@ -2180,7 +2241,7 @@ pub fn parse_value(
         if let (expr, None) = parse_range(working_set, span) {
             return (expr, None);
         } else {
-            return parse_full_column_path(working_set, None, span);
+            return parse_full_cell_path(working_set, None, span);
         }
     } else if bytes.starts_with(b"{") {
         if matches!(shape, SyntaxShape::Block(_)) || matches!(shape, SyntaxShape::Any) {
@@ -2480,453 +2541,6 @@ pub fn parse_variable(
     }
 }
 
-pub fn parse_def_predecl(working_set: &mut StateWorkingSet, spans: &[Span]) {
-    let name = working_set.get_span_contents(spans[0]);
-
-    if name == b"def" && spans.len() >= 4 {
-        let (name_expr, ..) = parse_string(working_set, spans[1]);
-        let name = name_expr.as_string();
-
-        working_set.enter_scope();
-        // FIXME: because parse_signature will update the scope with the variables it sees
-        // we end up parsing the signature twice per def. The first time is during the predecl
-        // so that we can see the types that are part of the signature, which we need for parsing.
-        // The second time is when we actually parse the body itworking_set.
-        // We can't reuse the first time because the variables that are created during parse_signature
-        // are lost when we exit the scope below.
-        let (sig, ..) = parse_signature(working_set, spans[2]);
-        let signature = sig.as_signature();
-        working_set.exit_scope();
-
-        if let (Some(name), Some(mut signature)) = (name, signature) {
-            signature.name = name;
-            let decl = signature.predeclare();
-
-            working_set.add_decl(decl);
-        }
-    }
-}
-
-pub fn parse_def(
-    working_set: &mut StateWorkingSet,
-    spans: &[Span],
-) -> (Statement, Option<ParseError>) {
-    let mut error = None;
-    let name = working_set.get_span_contents(spans[0]);
-
-    if name == b"def" && spans.len() >= 4 {
-        //FIXME: don't use expect here
-        let (name_expr, err) = parse_string(working_set, spans[1]);
-        error = error.or(err);
-
-        working_set.enter_scope();
-        let (sig, err) = parse_signature(working_set, spans[2]);
-        error = error.or(err);
-
-        let (block, err) =
-            parse_block_expression(working_set, &SyntaxShape::Block(Some(vec![])), spans[3]);
-        error = error.or(err);
-        working_set.exit_scope();
-
-        if error.is_some() {
-            return (
-                Statement::Pipeline(Pipeline::from_vec(vec![garbage(span(spans))])),
-                error,
-            );
-        }
-
-        let name = name_expr.as_string();
-
-        let signature = sig.as_signature();
-
-        let block_id = block.as_block();
-
-        match (name, signature, block_id) {
-            (Some(name), Some(mut signature), Some(block_id)) => {
-                let decl_id = working_set
-                    .find_decl(name.as_bytes())
-                    .expect("internal error: predeclaration failed to add definition");
-
-                let declaration = working_set.get_decl_mut(decl_id);
-
-                signature.name = name;
-
-                *declaration = signature.into_block_command(block_id);
-
-                let def_decl_id = working_set
-                    .find_decl(b"def")
-                    .expect("internal error: missing def command");
-
-                let call = Box::new(Call {
-                    head: spans[0],
-                    decl_id: def_decl_id,
-                    positional: vec![name_expr, sig, block],
-                    named: vec![],
-                });
-
-                (
-                    Statement::Pipeline(Pipeline::from_vec(vec![Expression {
-                        expr: Expr::Call(call),
-                        span: span(spans),
-                        ty: Type::Unknown,
-                        custom_completion: None,
-                    }])),
-                    error,
-                )
-            }
-            _ => (
-                Statement::Pipeline(Pipeline::from_vec(vec![garbage(span(spans))])),
-                error,
-            ),
-        }
-    } else {
-        (
-            garbage_statement(spans),
-            Some(ParseError::UnknownState(
-                "Expected structure: def <name> [] {}".into(),
-                span(spans),
-            )),
-        )
-    }
-}
-
-pub fn parse_alias(
-    working_set: &mut StateWorkingSet,
-    spans: &[Span],
-) -> (Statement, Option<ParseError>) {
-    let name = working_set.get_span_contents(spans[0]);
-
-    if name == b"alias" {
-        if let Some((span, err)) = check_name(working_set, spans) {
-            return (
-                Statement::Pipeline(Pipeline::from_vec(vec![garbage(*span)])),
-                Some(err),
-            );
-        }
-
-        if let Some(decl_id) = working_set.find_decl(b"alias") {
-            let (call, call_span, _) =
-                parse_internal_call(working_set, spans[0], &spans[1..], decl_id);
-
-            if spans.len() >= 4 {
-                let alias_name = working_set.get_span_contents(spans[1]);
-
-                let alias_name = if alias_name.starts_with(b"\"")
-                    && alias_name.ends_with(b"\"")
-                    && alias_name.len() > 1
-                {
-                    alias_name[1..(alias_name.len() - 1)].to_vec()
-                } else {
-                    alias_name.to_vec()
-                };
-                let _equals = working_set.get_span_contents(spans[2]);
-
-                let replacement = spans[3..].to_vec();
-
-                //println!("{:?} {:?}", alias_name, replacement);
-
-                working_set.add_alias(alias_name, replacement);
-            }
-
-            return (
-                Statement::Pipeline(Pipeline::from_vec(vec![Expression {
-                    expr: Expr::Call(call),
-                    span: call_span,
-                    ty: Type::Unknown,
-                    custom_completion: None,
-                }])),
-                None,
-            );
-        }
-    }
-
-    (
-        garbage_statement(spans),
-        Some(ParseError::UnknownState(
-            "internal error: alias statement unparseable".into(),
-            span(spans),
-        )),
-    )
-}
-
-pub fn parse_module(
-    working_set: &mut StateWorkingSet,
-    spans: &[Span],
-) -> (Statement, Option<ParseError>) {
-    // TODO: Currently, module is closing over its parent scope (i.e., defs in the parent scope are
-    // visible and usable in this module's scope). We might want to disable that. How?
-
-    let mut error = None;
-    let bytes = working_set.get_span_contents(spans[0]);
-
-    // parse_def() equivalent
-    if bytes == b"module" && spans.len() >= 3 {
-        let (module_name_expr, err) = parse_string(working_set, spans[1]);
-        error = error.or(err);
-
-        let module_name = module_name_expr
-            .as_string()
-            .expect("internal error: module name is not a string");
-
-        // parse_block_expression() equivalent
-        let block_span = spans[2];
-        let block_bytes = working_set.get_span_contents(block_span);
-        let mut start = block_span.start;
-        let mut end = block_span.end;
-
-        if block_bytes.starts_with(b"{") {
-            start += 1;
-        } else {
-            return (
-                garbage_statement(spans),
-                Some(ParseError::Expected("block".into(), block_span)),
-            );
-        }
-
-        if block_bytes.ends_with(b"}") {
-            end -= 1;
-        } else {
-            error = error.or_else(|| {
-                Some(ParseError::Unclosed(
-                    "}".into(),
-                    Span {
-                        start: end,
-                        end: end + 1,
-                    },
-                ))
-            });
-        }
-
-        let block_span = Span { start, end };
-
-        let source = working_set.get_span_contents(block_span);
-
-        let (output, err) = lex(source, start, &[], &[]);
-        error = error.or(err);
-
-        working_set.enter_scope();
-
-        // Do we need block parameters?
-
-        let (output, err) = lite_parse(&output);
-        error = error.or(err);
-
-        // We probably don't need $it
-
-        // we're doing parse_block() equivalent
-        // let (mut output, err) = parse_block(working_set, &output, false);
-
-        for pipeline in &output.block {
-            if pipeline.commands.len() == 1 {
-                parse_def_predecl(working_set, &pipeline.commands[0].parts);
-            }
-        }
-
-        let mut exports: Vec<(Vec<u8>, DeclId)> = vec![];
-
-        let block: Block = output
-            .block
-            .iter()
-            .map(|pipeline| {
-                if pipeline.commands.len() == 1 {
-                    // this one here is doing parse_statement() equivalent
-                    // let (stmt, err) = parse_statement(working_set, &pipeline.commands[0].parts);
-                    let name = working_set.get_span_contents(pipeline.commands[0].parts[0]);
-
-                    let (stmt, err) = match name {
-                        // TODO: Here we can add other stuff that's alowed for modules
-                        b"def" => {
-                            let (stmt, err) = parse_def(working_set, &pipeline.commands[0].parts);
-
-                            if err.is_none() {
-                                let decl_name =
-                                    working_set.get_span_contents(pipeline.commands[0].parts[1]);
-
-                                let decl_id = working_set
-                                    .find_decl(decl_name)
-                                    .expect("internal error: failed to find added declaration");
-
-                                // TODO: Later, we want to put this behind 'export'
-                                exports.push((decl_name.into(), decl_id));
-                            }
-
-                            (stmt, err)
-                        }
-                        _ => (
-                            garbage_statement(&pipeline.commands[0].parts),
-                            Some(ParseError::Expected("def".into(), block_span)),
-                        ),
-                    };
-
-                    if error.is_none() {
-                        error = err;
-                    }
-
-                    stmt
-                } else {
-                    error = Some(ParseError::Expected("not a pipeline".into(), block_span));
-                    garbage_statement(spans)
-                }
-            })
-            .into();
-
-        let block = block.with_exports(exports);
-
-        working_set.exit_scope();
-
-        let block_id = working_set.add_module(&module_name, block);
-
-        let block_expr = Expression {
-            expr: Expr::Block(block_id),
-            span: block_span,
-            ty: Type::Block,
-            custom_completion: None,
-        };
-
-        let module_decl_id = working_set
-            .find_decl(b"module")
-            .expect("internal error: missing module command");
-
-        let call = Box::new(Call {
-            head: spans[0],
-            decl_id: module_decl_id,
-            positional: vec![module_name_expr, block_expr],
-            named: vec![],
-        });
-
-        (
-            Statement::Pipeline(Pipeline::from_vec(vec![Expression {
-                expr: Expr::Call(call),
-                span: span(spans),
-                ty: Type::Unknown,
-                custom_completion: None,
-            }])),
-            error,
-        )
-    } else {
-        (
-            garbage_statement(spans),
-            Some(ParseError::UnknownState(
-                "Expected structure: module <name> {}".into(),
-                span(spans),
-            )),
-        )
-    }
-}
-
-pub fn parse_use(
-    working_set: &mut StateWorkingSet,
-    spans: &[Span],
-) -> (Statement, Option<ParseError>) {
-    let mut error = None;
-    let bytes = working_set.get_span_contents(spans[0]);
-
-    // TODO: Currently, this directly imports the module's definitions into the current scope.
-    // Later, we want to put them behind the module's name and add selective importing
-    if bytes == b"use" && spans.len() >= 2 {
-        let (module_name_expr, err) = parse_string(working_set, spans[1]);
-        error = error.or(err);
-
-        let module_name = module_name_expr
-            .as_string()
-            .expect("internal error: module name is not a string");
-
-        let module_name_bytes = module_name.as_bytes().to_vec();
-
-        let exports = if let Some(block_id) = working_set.find_module(&module_name_bytes) {
-            // TODO: Since we don't use the Block at all, we might just as well create a separate
-            // Module that holds only the exports, without having Blocks in the way.
-            working_set.get_block(block_id).exports.clone()
-        } else {
-            return (
-                garbage_statement(spans),
-                Some(ParseError::ModuleNotFound(spans[1])),
-            );
-        };
-
-        // Extend the current scope with the module's exports
-        working_set.activate_overlay(exports);
-
-        // Create the Use command call
-        let use_decl_id = working_set
-            .find_decl(b"use")
-            .expect("internal error: missing use command");
-
-        let call = Box::new(Call {
-            head: spans[0],
-            decl_id: use_decl_id,
-            positional: vec![module_name_expr],
-            named: vec![],
-        });
-
-        (
-            Statement::Pipeline(Pipeline::from_vec(vec![Expression {
-                expr: Expr::Call(call),
-                span: span(spans),
-                ty: Type::Unknown,
-                custom_completion: None,
-            }])),
-            error,
-        )
-    } else {
-        (
-            garbage_statement(spans),
-            Some(ParseError::UnknownState(
-                "Expected structure: use <name>".into(),
-                span(spans),
-            )),
-        )
-    }
-}
-
-pub fn parse_let(
-    working_set: &mut StateWorkingSet,
-    spans: &[Span],
-) -> (Statement, Option<ParseError>) {
-    let name = working_set.get_span_contents(spans[0]);
-
-    if name == b"let" {
-        if let Some((span, err)) = check_name(working_set, spans) {
-            return (
-                Statement::Pipeline(Pipeline::from_vec(vec![garbage(*span)])),
-                Some(err),
-            );
-        }
-
-        if let Some(decl_id) = working_set.find_decl(b"let") {
-            let (call, call_span, err) =
-                parse_internal_call(working_set, spans[0], &spans[1..], decl_id);
-
-            // Update the variable to the known type if we can.
-            if err.is_none() {
-                let var_id = call.positional[0]
-                    .as_var()
-                    .expect("internal error: expected variable");
-                let rhs_type = call.positional[1].ty.clone();
-
-                working_set.set_variable_type(var_id, rhs_type);
-            }
-
-            return (
-                Statement::Pipeline(Pipeline::from_vec(vec![Expression {
-                    expr: Expr::Call(call),
-                    span: call_span,
-                    ty: Type::Unknown,
-                    custom_completion: None,
-                }])),
-                err,
-            );
-        }
-    }
-    (
-        garbage_statement(spans),
-        Some(ParseError::UnknownState(
-            "internal error: let statement unparseable".into(),
-            span(spans),
-        )),
-    )
-}
-
 pub fn parse_statement(
     working_set: &mut StateWorkingSet,
     spans: &[Span],

crates/nu-protocol/src/ast/import_pattern.rs

@@ -0,0 +1,13 @@
+use crate::Span;
+
+#[derive(Debug, Clone)]
+pub enum ImportPatternMember {
+    Glob { span: Span },
+    Name { name: Vec<u8>, span: Span },
+}
+
+#[derive(Debug, Clone)]
+pub struct ImportPattern {
+    pub head: Vec<u8>,
+    pub members: Vec<ImportPatternMember>,
+}

crates/nu-protocol/src/ast/mod.rs

@@ -3,6 +3,7 @@ mod call;
 mod cell_path;
 mod expr;
 mod expression;
+mod import_pattern;
 mod operator;
 mod pipeline;
 mod statement;
@@ -12,6 +13,7 @@ pub use call::*;
 pub use cell_path::*;
 pub use expr::*;
 pub use expression::*;
+pub use import_pattern::*;
 pub use operator::*;
 pub use pipeline::*;
 pub use statement::*;

crates/nu-protocol/src/syntax_shape.rs

@@ -33,6 +33,9 @@ pub enum SyntaxShape {
     /// A glob pattern is allowed, eg `foo*`
     GlobPattern,
 
+    /// A module path pattern used for imports
+    ImportPattern,
+
     /// A block is allowed, eg `{start this thing}`
     Block(Option<Vec<SyntaxShape>>),
 
@@ -87,6 +90,7 @@ impl SyntaxShape {
             SyntaxShape::Filesize => Type::Filesize,
             SyntaxShape::FullCellPath => Type::Unknown,
             SyntaxShape::GlobPattern => Type::String,
+            SyntaxShape::ImportPattern => Type::Unknown,
             SyntaxShape::Int => Type::Int,
             SyntaxShape::List(x) => {
                 let contents = x.to_type();

crates/nu-protocol/src/value/mod.rs

@@ -177,9 +177,9 @@ impl Value {
         }
     }
 
-    pub fn follow_cell_path(self, column_path: &[PathMember]) -> Result<Value, ShellError> {
+    pub fn follow_cell_path(self, cell_path: &[PathMember]) -> Result<Value, ShellError> {
         let mut current = self;
-        for member in column_path {
+        for member in cell_path {
             // FIXME: this uses a few extra clones for simplicity, but there may be a way
             // to traverse the path without them
             match member {

src/tests.rs

@@ -342,3 +342,35 @@ fn better_block_types() -> TestResult {
         "1 is 2",
     )
 }
+
+#[test]
+fn module_imports_1() -> TestResult {
+    run_test(
+        r#"module foo { def a [] { 1 }; def b [] { 2 } }; use foo; foo.a"#,
+        "1",
+    )
+}
+
+#[test]
+fn module_imports_2() -> TestResult {
+    run_test(
+        r#"module foo { def a [] { 1 }; def b [] { 2 } }; use foo.a; a"#,
+        "1",
+    )
+}
+
+#[test]
+fn module_imports_3() -> TestResult {
+    run_test(
+        r#"module foo { def a [] { 1 }; def b [] { 2 } }; use foo.*; b"#,
+        "2",
+    )
+}
+
+#[test]
+fn module_imports_4() -> TestResult {
+    fail_test(
+        r#"module foo { def a [] { 1 }; def b [] { 2 } }; use foo.c"#,
+        "not find import",
+    )
+}