Add support for var/string interp for external names (#729)

crates/nu-command/src/system/run_external.rs

@@ -260,7 +260,18 @@ impl<'call> ExternalCommand<'call> {
 
     /// Spawn a command without shelling out to an external shell
     fn spawn_simple_command(&self, cwd: &str) -> std::process::Command {
-        let mut process = std::process::Command::new(&self.name.item);
+        let head = trim_enclosing_quotes(&self.name.item);
+        let head = if head.starts_with('~') || head.starts_with("..") {
+            nu_path::expand_path_with(head, cwd)
+                .to_string_lossy()
+                .to_string()
+        } else {
+            head
+        };
+
+        let head = head.replace("\\", "\\\\");
+
+        let mut process = std::process::Command::new(&head);
 
         for arg in &self.args {
             let arg = trim_enclosing_quotes(arg);

crates/nu-engine/src/eval.rs

@@ -6,7 +6,7 @@ use nu_protocol::ast::{Block, Call, Expr, Expression, Operator, Statement};
 use nu_protocol::engine::{EngineState, Stack};
 use nu_protocol::{
     IntoInterruptiblePipelineData, IntoPipelineData, PipelineData, Range, ShellError, Span,
-    Spanned, Type, Unit, Value, VarId, ENV_VARIABLE_ID,
+    Spanned, Unit, Value, VarId, ENV_VARIABLE_ID,
 };
 
 use crate::{current_dir_str, get_full_help};
@@ -139,26 +139,20 @@ fn eval_call(
 fn eval_external(
     engine_state: &EngineState,
     stack: &mut Stack,
-    name: &str,
-    name_span: &Span,
+    head: &Expression,
     args: &[Expression],
     input: PipelineData,
     last_expression: bool,
 ) -> Result<PipelineData, ShellError> {
     let decl_id = engine_state
         .find_decl("run_external".as_bytes())
-        .ok_or_else(|| ShellError::ExternalNotSupported(*name_span))?;
+        .ok_or(ShellError::ExternalNotSupported(head.span))?;
 
     let command = engine_state.get_decl(decl_id);
 
     let mut call = Call::new();
 
-    call.positional.push(Expression {
-        expr: Expr::String(name.trim_start_matches('^').to_string()),
-        span: *name_span,
-        ty: Type::String,
-        custom_completion: None,
-    });
+    call.positional.push(head.clone());
 
     for arg in args {
         call.positional.push(arg.clone())
@@ -168,7 +162,7 @@ fn eval_external(
         call.named.push((
             Spanned {
                 item: "last_expression".into(),
-                span: *name_span,
+                span: head.span,
             },
             None,
         ))
@@ -246,18 +240,18 @@ pub fn eval_expression(
                     .into_value(call.head),
             )
         }
-        Expr::ExternalCall(name, span, args) => {
+        Expr::ExternalCall(head, args) => {
+            let span = head.span;
             // FIXME: protect this collect with ctrl-c
             Ok(eval_external(
                 engine_state,
                 stack,
-                name,
-                span,
+                head,
                 args,
-                PipelineData::new(*span),
+                PipelineData::new(span),
                 false,
             )?
-            .into_value(*span))
+            .into_value(span))
         }
         Expr::Operator(_) => Ok(Value::Nothing { span: expr.span }),
         Expr::BinaryOp(lhs, op, rhs) => {
@@ -413,14 +407,13 @@ pub fn eval_block(
                         input = eval_call(engine_state, stack, call, input)?;
                     }
                     Expression {
-                        expr: Expr::ExternalCall(name, name_span, args),
+                        expr: Expr::ExternalCall(head, args),
                         ..
                     } => {
                         input = eval_external(
                             engine_state,
                             stack,
-                            name,
-                            name_span,
+                            head,
                             args,
                             input,
                             i == pipeline.expressions.len() - 1,
@@ -511,18 +504,10 @@ pub fn eval_subexpression(
                         input = eval_call(engine_state, stack, call, input)?;
                     }
                     Expression {
-                        expr: Expr::ExternalCall(name, name_span, args),
+                        expr: Expr::ExternalCall(head, args),
                         ..
                     } => {
-                        input = eval_external(
-                            engine_state,
-                            stack,
-                            name,
-                            name_span,
-                            args,
-                            input,
-                            false,
-                        )?;
+                        input = eval_external(engine_state, stack, head, args, input, false)?;
                     }
 
                     elem => {

crates/nu-parser/src/flatten.rs

@@ -156,8 +156,21 @@ pub fn flatten_expression(
             output.extend(args);
             output
         }
-        Expr::ExternalCall(_, name_span, args) => {
-            let mut output = vec![(*name_span, FlatShape::External)];
+        Expr::ExternalCall(head, args) => {
+            let mut output = vec![];
+
+            match **head {
+                Expression {
+                    expr: Expr::String(..),
+                    span,
+                    ..
+                } => {
+                    output.push((span, FlatShape::External));
+                }
+                _ => {
+                    output.extend(flatten_expression(working_set, head));
+                }
+            }
 
             for arg in args {
                 //output.push((*arg, FlatShape::ExternalArg));

crates/nu-parser/src/parser.rs

@@ -191,19 +191,35 @@ pub fn parse_external_call(
     spans: &[Span],
 ) -> (Expression, Option<ParseError>) {
     let mut args = vec![];
-    let name_span = spans[0];
-    let name = String::from_utf8_lossy(working_set.get_span_contents(name_span)).to_string();
-    let cwd = working_set.get_cwd();
-    let name = if name.starts_with('.') || name.starts_with('~') {
-        nu_path::expand_path_with(name, cwd)
-            .to_string_lossy()
-            .to_string()
+
+    let head_contents = working_set.get_span_contents(spans[0]);
+
+    let head_span = if head_contents.starts_with(b"^") {
+        Span {
+            start: spans[0].start + 1,
+            end: spans[0].end,
+        }
     } else {
-        name
+        spans[0]
     };
 
+    let head_contents = working_set.get_span_contents(head_span);
+
     let mut error = None;
 
+    let head = if head_contents.starts_with(b"$") || head_contents.starts_with(b"(") {
+        let (arg, err) = parse_expression(working_set, &[head_span], true);
+        error = error.or(err);
+        Box::new(arg)
+    } else {
+        Box::new(Expression {
+            expr: Expr::String(String::from_utf8_lossy(head_contents).to_string()),
+            span: head_span,
+            ty: Type::String,
+            custom_completion: None,
+        })
+    };
+
     for span in &spans[1..] {
         let contents = working_set.get_span_contents(*span);
 
@@ -222,7 +238,7 @@ pub fn parse_external_call(
     }
     (
         Expression {
-            expr: Expr::ExternalCall(name, name_span, args),
+            expr: Expr::ExternalCall(head, args),
             span: span(spans),
             ty: Type::Unknown,
             custom_completion: None,
@@ -3684,7 +3700,10 @@ pub fn find_captures_in_expr(
             }
         }
         Expr::CellPath(_) => {}
-        Expr::ExternalCall(_, _, exprs) => {
+        Expr::ExternalCall(head, exprs) => {
+            let result = find_captures_in_expr(working_set, head, seen);
+            output.extend(&result);
+
             for expr in exprs {
                 let result = find_captures_in_expr(working_set, expr, seen);
                 output.extend(&result);

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

@@ -15,7 +15,7 @@ pub enum Expr {
     Var(VarId),
     VarDecl(VarId),
     Call(Box<Call>),
-    ExternalCall(String, Span, Vec<Expression>),
+    ExternalCall(Box<Expression>, Vec<Expression>),
     Operator(Operator),
     RowCondition(BlockId),
     BinaryOp(Box<Expression>, Box<Expression>, Box<Expression>), //lhs, op, rhs

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

@@ -142,7 +142,10 @@ impl Expression {
                 false
             }
             Expr::CellPath(_) => false,
-            Expr::ExternalCall(_, _, args) => {
+            Expr::ExternalCall(head, args) => {
+                if head.has_in_variable(working_set) {
+                    return true;
+                }
                 for arg in args {
                     if arg.has_in_variable(working_set) {
                         return true;
@@ -298,7 +301,8 @@ impl Expression {
                 }
             }
             Expr::CellPath(_) => {}
-            Expr::ExternalCall(_, _, args) => {
+            Expr::ExternalCall(head, args) => {
+                head.replace_in_variable(working_set, new_var_id);
                 for arg in args {
                     arg.replace_in_variable(working_set, new_var_id)
                 }