Add commands

Cargo.lock

@@ -162,6 +162,7 @@ dependencies = [
  "assert_cmd",
  "codespan-reporting",
  "nu-cli",
+ "nu-command",
  "nu-engine",
  "nu-parser",
  "nu-protocol",
@@ -300,6 +301,10 @@ dependencies = [
 [[package]]
 name = "nu-command"
 version = "0.1.0"
+dependencies = [
+ "nu-engine",
+ "nu-protocol",
+]
 
 [[package]]
 name = "nu-engine"

Cargo.toml

@@ -12,6 +12,7 @@ members = ["crates/nu-cli", "crates/nu-engine", "crates/nu-parser", "crates/nu-c
 reedline = { git = "https://github.com/jntrnr/reedline", branch = "main" }
 codespan-reporting = "0.11.1"
 nu-cli = { path="./crates/nu-cli" }
+nu-command = { path="./crates/nu-command" }
 nu-engine = { path="./crates/nu-engine" }
 nu-parser = { path="./crates/nu-parser" }
 nu-protocol = { path = "./crates/nu-protocol" }

crates/nu-cli/src/default_context.rs

@@ -1,118 +0,0 @@
-use std::{cell::RefCell, rc::Rc};
-
-use nu_protocol::{
-    engine::{EngineState, StateWorkingSet},
-    Signature, SyntaxShape,
-};
-
-pub fn create_default_context() -> Rc<RefCell<EngineState>> {
-    let engine_state = Rc::new(RefCell::new(EngineState::new()));
-    let delta = {
-        let engine_state = engine_state.borrow();
-        let mut working_set = StateWorkingSet::new(&*engine_state);
-
-        let sig =
-            Signature::build("where").required("cond", SyntaxShape::RowCondition, "condition");
-        working_set.add_decl(sig.predeclare());
-
-        let sig = Signature::build("if")
-            .required("cond", SyntaxShape::Expression, "condition")
-            .required("then_block", SyntaxShape::Block, "then block")
-            .optional(
-                "else",
-                SyntaxShape::Keyword(b"else".to_vec(), Box::new(SyntaxShape::Expression)),
-                "optional else followed by else block",
-            );
-        working_set.add_decl(sig.predeclare());
-
-        let sig = Signature::build("let")
-            .required("var_name", SyntaxShape::VarWithOptType, "variable name")
-            .required(
-                "initial_value",
-                SyntaxShape::Keyword(b"=".to_vec(), Box::new(SyntaxShape::Expression)),
-                "equals sign followed by value",
-            );
-        working_set.add_decl(sig.predeclare());
-
-        let sig = Signature::build("let-env")
-            .required("var_name", SyntaxShape::String, "variable name")
-            .required(
-                "initial_value",
-                SyntaxShape::Keyword(b"=".to_vec(), Box::new(SyntaxShape::String)),
-                "equals sign followed by value",
-            );
-        working_set.add_decl(sig.predeclare());
-
-        let sig = Signature::build("alias")
-            .required("name", SyntaxShape::String, "name of the alias")
-            .required(
-                "initial_value",
-                SyntaxShape::Keyword(b"=".to_vec(), Box::new(SyntaxShape::Expression)),
-                "equals sign followed by value",
-            );
-        working_set.add_decl(sig.predeclare());
-
-        let sig = Signature::build("build-string").rest(SyntaxShape::String, "list of string");
-        working_set.add_decl(sig.predeclare());
-
-        let sig = Signature::build("def")
-            .required("def_name", SyntaxShape::String, "definition name")
-            .required("params", SyntaxShape::Signature, "parameters")
-            .required("block", SyntaxShape::Block, "body of the definition");
-        working_set.add_decl(sig.predeclare());
-
-        let sig = Signature::build("for")
-            .required(
-                "var_name",
-                SyntaxShape::Variable,
-                "name of the looping variable",
-            )
-            .required(
-                "range",
-                SyntaxShape::Keyword(b"in".to_vec(), Box::new(SyntaxShape::Int)),
-                "range of the loop",
-            )
-            .required("block", SyntaxShape::Block, "the block to run");
-        working_set.add_decl(sig.predeclare());
-
-        let sig =
-            Signature::build("benchmark").required("block", SyntaxShape::Block, "the block to run");
-        working_set.add_decl(sig.predeclare());
-
-        // let sig = Signature::build("foo").named("--jazz", SyntaxShape::Int, "jazz!!", Some('j'));
-        // working_set.add_decl(sig.into());
-
-        // let sig = Signature::build("bar")
-        //     .named("--jazz", SyntaxShape::Int, "jazz!!", Some('j'))
-        //     .switch("--rock", "rock!!", Some('r'));
-        // working_set.add_decl(sig.into());
-        let sig = Signature::build("exit");
-        working_set.add_decl(sig.predeclare());
-        let sig = Signature::build("vars");
-        working_set.add_decl(sig.predeclare());
-        let sig = Signature::build("decls");
-        working_set.add_decl(sig.predeclare());
-        let sig = Signature::build("blocks");
-        working_set.add_decl(sig.predeclare());
-        let sig = Signature::build("stack");
-        working_set.add_decl(sig.predeclare());
-
-        let sig = Signature::build("add");
-        working_set.add_decl(sig.predeclare());
-        let sig = Signature::build("add it");
-        working_set.add_decl(sig.predeclare());
-
-        let sig = Signature::build("add it together")
-            .required("x", SyntaxShape::Int, "x value")
-            .required("y", SyntaxShape::Int, "y value");
-        working_set.add_decl(sig.predeclare());
-
-        working_set.render()
-    };
-
-    {
-        EngineState::merge_delta(&mut *engine_state.borrow_mut(), delta);
-    }
-
-    engine_state
-}

crates/nu-cli/src/lib.rs

@@ -1,7 +1,5 @@
-mod default_context;
 mod errors;
 mod syntax_highlight;
 
-pub use default_context::create_default_context;
 pub use errors::{report_parsing_error, report_shell_error};
 pub use syntax_highlight::NuHighlighter;

crates/nu-command/Cargo.toml

@@ -6,3 +6,5 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+nu-protocol = { path = "../nu-protocol" }
+nu-engine = { path = "../nu-engine" }

crates/nu-command/src/alias.rs

@@ -0,0 +1,34 @@
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EvaluationContext};
+use nu_protocol::{Signature, SyntaxShape, Value};
+
+pub struct Alias;
+
+impl Command for Alias {
+    fn name(&self) -> &str {
+        "alias"
+    }
+
+    fn usage(&self) -> &str {
+        "Alias a command (with optional flags) to a new name"
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("alias")
+            .required("name", SyntaxShape::String, "name of the alias")
+            .required(
+                "initial_value",
+                SyntaxShape::Keyword(b"=".to_vec(), Box::new(SyntaxShape::Expression)),
+                "equals sign followed by value",
+            )
+    }
+
+    fn run(
+        &self,
+        _context: &EvaluationContext,
+        call: &Call,
+        _input: Value,
+    ) -> Result<nu_protocol::Value, nu_protocol::ShellError> {
+        Ok(Value::Nothing { span: call.head })
+    }
+}

crates/nu-command/src/benchmark.rs

@@ -0,0 +1,44 @@
+use std::time::Instant;
+
+use nu_engine::eval_block;
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EvaluationContext};
+use nu_protocol::{Signature, SyntaxShape, Value};
+
+pub struct Benchmark;
+
+impl Command for Benchmark {
+    fn name(&self) -> &str {
+        "benchmark"
+    }
+
+    fn usage(&self) -> &str {
+        "Time the running time of a block"
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("benchmark").required("block", SyntaxShape::Block, "the block to run")
+    }
+
+    fn run(
+        &self,
+        context: &EvaluationContext,
+        call: &Call,
+        _input: Value,
+    ) -> Result<nu_protocol::Value, nu_protocol::ShellError> {
+        let block = call.positional[0]
+            .as_block()
+            .expect("internal error: expected block");
+        let engine_state = context.engine_state.borrow();
+        let block = engine_state.get_block(block);
+
+        let state = context.enter_scope();
+        let start_time = Instant::now();
+        eval_block(&state, block)?;
+        let end_time = Instant::now();
+        println!("{} ms", (end_time - start_time).as_millis());
+        Ok(Value::Nothing {
+            span: call.positional[0].span,
+        })
+    }
+}

crates/nu-command/src/build_string.rs

@@ -0,0 +1,39 @@
+use nu_engine::eval_expression;
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EvaluationContext};
+use nu_protocol::{Signature, SyntaxShape, Value};
+
+pub struct BuildString;
+
+impl Command for BuildString {
+    fn name(&self) -> &str {
+        "build-string"
+    }
+
+    fn usage(&self) -> &str {
+        "Create a string from the arguments."
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("build-string").rest(SyntaxShape::String, "list of string")
+    }
+
+    fn run(
+        &self,
+        context: &EvaluationContext,
+        call: &Call,
+        _input: Value,
+    ) -> Result<nu_protocol::Value, nu_protocol::ShellError> {
+        let mut output = vec![];
+
+        for expr in &call.positional {
+            let val = eval_expression(context, expr)?;
+
+            output.push(val.into_string());
+        }
+        Ok(Value::String {
+            val: output.join(""),
+            span: call.head,
+        })
+    }
+}

crates/nu-command/src/def.rs

@@ -0,0 +1,31 @@
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EvaluationContext};
+use nu_protocol::{Signature, SyntaxShape, Value};
+
+pub struct Def;
+
+impl Command for Def {
+    fn name(&self) -> &str {
+        "def"
+    }
+
+    fn usage(&self) -> &str {
+        "Define a custom command"
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("def")
+            .required("def_name", SyntaxShape::String, "definition name")
+            .required("params", SyntaxShape::Signature, "parameters")
+            .required("block", SyntaxShape::Block, "body of the definition")
+    }
+
+    fn run(
+        &self,
+        _context: &EvaluationContext,
+        call: &Call,
+        _input: Value,
+    ) -> Result<nu_protocol::Value, nu_protocol::ShellError> {
+        Ok(Value::Nothing { span: call.head })
+    }
+}

crates/nu-command/src/default_context.rs

@@ -0,0 +1,55 @@
+use std::{cell::RefCell, rc::Rc};
+
+use nu_protocol::{
+    engine::{EngineState, StateWorkingSet},
+    Signature, SyntaxShape,
+};
+
+use crate::{Alias, Benchmark, BuildString, Def, For, If, Let, LetEnv};
+
+pub fn create_default_context() -> Rc<RefCell<EngineState>> {
+    let engine_state = Rc::new(RefCell::new(EngineState::new()));
+    let delta = {
+        let engine_state = engine_state.borrow();
+        let mut working_set = StateWorkingSet::new(&*engine_state);
+
+        let sig =
+            Signature::build("where").required("cond", SyntaxShape::RowCondition, "condition");
+        working_set.add_decl(sig.predeclare());
+
+        working_set.add_decl(Box::new(If));
+
+        working_set.add_decl(Box::new(Let));
+
+        working_set.add_decl(Box::new(LetEnv));
+
+        working_set.add_decl(Box::new(Alias));
+
+        working_set.add_decl(Box::new(BuildString));
+
+        working_set.add_decl(Box::new(Def));
+
+        working_set.add_decl(Box::new(For));
+
+        working_set.add_decl(Box::new(Benchmark));
+
+        let sig = Signature::build("exit");
+        working_set.add_decl(sig.predeclare());
+        let sig = Signature::build("vars");
+        working_set.add_decl(sig.predeclare());
+        let sig = Signature::build("decls");
+        working_set.add_decl(sig.predeclare());
+        let sig = Signature::build("blocks");
+        working_set.add_decl(sig.predeclare());
+        let sig = Signature::build("stack");
+        working_set.add_decl(sig.predeclare());
+
+        working_set.render()
+    };
+
+    {
+        EngineState::merge_delta(&mut *engine_state.borrow_mut(), delta);
+    }
+
+    engine_state
+}

crates/nu-command/src/for_.rs

@@ -0,0 +1,75 @@
+use nu_engine::{eval_block, eval_expression};
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EvaluationContext};
+use nu_protocol::{Signature, Span, SyntaxShape, Value};
+
+pub struct For;
+
+impl Command for For {
+    fn name(&self) -> &str {
+        "for"
+    }
+
+    fn usage(&self) -> &str {
+        "Loop over a range"
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("for")
+            .required(
+                "var_name",
+                SyntaxShape::Variable,
+                "name of the looping variable",
+            )
+            .required(
+                "range",
+                SyntaxShape::Keyword(b"in".to_vec(), Box::new(SyntaxShape::Int)),
+                "range of the loop",
+            )
+            .required("block", SyntaxShape::Block, "the block to run")
+    }
+
+    fn run(
+        &self,
+        context: &EvaluationContext,
+        call: &Call,
+        _input: Value,
+    ) -> Result<nu_protocol::Value, nu_protocol::ShellError> {
+        let var_id = call.positional[0]
+            .as_var()
+            .expect("internal error: missing variable");
+
+        let keyword_expr = call.positional[1]
+            .as_keyword()
+            .expect("internal error: missing keyword");
+        let end_val = eval_expression(context, keyword_expr)?;
+
+        let block = call.positional[2]
+            .as_block()
+            .expect("internal error: expected block");
+        let engine_state = context.engine_state.borrow();
+        let block = engine_state.get_block(block);
+
+        let state = context.enter_scope();
+
+        let mut x = Value::Int {
+            val: 0,
+            span: Span::unknown(),
+        };
+
+        loop {
+            if x == end_val {
+                break;
+            } else {
+                state.add_var(var_id, x.clone());
+                eval_block(&state, block)?;
+            }
+            if let Value::Int { ref mut val, .. } = x {
+                *val += 1
+            }
+        }
+        Ok(Value::Nothing {
+            span: call.positional[0].span,
+        })
+    }
+}

crates/nu-command/src/if_.rs

@@ -0,0 +1,67 @@
+use nu_engine::{eval_block, eval_expression};
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EvaluationContext};
+use nu_protocol::{ShellError, Signature, SyntaxShape, Value};
+
+pub struct If;
+
+impl Command for If {
+    fn name(&self) -> &str {
+        "if"
+    }
+
+    fn usage(&self) -> &str {
+        "Create a variable and give it a value."
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("if")
+            .required("cond", SyntaxShape::Expression, "condition")
+            .required("then_block", SyntaxShape::Block, "then block")
+            .optional(
+                "else",
+                SyntaxShape::Keyword(b"else".to_vec(), Box::new(SyntaxShape::Expression)),
+                "optional else followed by else block",
+            )
+    }
+
+    fn run(
+        &self,
+        context: &EvaluationContext,
+        call: &Call,
+        _input: Value,
+    ) -> Result<nu_protocol::Value, nu_protocol::ShellError> {
+        let cond = &call.positional[0];
+        let then_block = call.positional[1]
+            .as_block()
+            .expect("internal error: expected block");
+        let else_case = call.positional.get(2);
+
+        let result = eval_expression(context, cond)?;
+        match result {
+            Value::Bool { val, span } => {
+                let engine_state = context.engine_state.borrow();
+                if val {
+                    let block = engine_state.get_block(then_block);
+                    let state = context.enter_scope();
+                    eval_block(&state, block)
+                } else if let Some(else_case) = else_case {
+                    if let Some(else_expr) = else_case.as_keyword() {
+                        if let Some(block_id) = else_expr.as_block() {
+                            let block = engine_state.get_block(block_id);
+                            let state = context.enter_scope();
+                            eval_block(&state, block)
+                        } else {
+                            eval_expression(context, else_expr)
+                        }
+                    } else {
+                        eval_expression(context, else_case)
+                    }
+                } else {
+                    Ok(Value::Nothing { span })
+                }
+            }
+            _ => Err(ShellError::CantConvert("bool".into(), result.span())),
+        }
+    }
+}

crates/nu-command/src/let_.rs

@@ -0,0 +1,50 @@
+use nu_engine::eval_expression;
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EvaluationContext};
+use nu_protocol::{Signature, SyntaxShape, Value};
+
+pub struct Let;
+
+impl Command for Let {
+    fn name(&self) -> &str {
+        "let"
+    }
+
+    fn usage(&self) -> &str {
+        "Create a variable and give it a value."
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("let")
+            .required("var_name", SyntaxShape::VarWithOptType, "variable name")
+            .required(
+                "initial_value",
+                SyntaxShape::Keyword(b"=".to_vec(), Box::new(SyntaxShape::Expression)),
+                "equals sign followed by value",
+            )
+    }
+
+    fn run(
+        &self,
+        context: &EvaluationContext,
+        call: &Call,
+        _input: Value,
+    ) -> Result<nu_protocol::Value, nu_protocol::ShellError> {
+        let var_id = call.positional[0]
+            .as_var()
+            .expect("internal error: missing variable");
+
+        let keyword_expr = call.positional[1]
+            .as_keyword()
+            .expect("internal error: missing keyword");
+
+        let rhs = eval_expression(context, keyword_expr)?;
+
+        //println!("Adding: {:?} to {}", rhs, var_id);
+
+        context.add_var(var_id, rhs);
+        Ok(Value::Nothing {
+            span: call.positional[0].span,
+        })
+    }
+}

crates/nu-command/src/let_env.rs

@@ -0,0 +1,51 @@
+use nu_engine::eval_expression;
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EvaluationContext};
+use nu_protocol::{Signature, SyntaxShape, Value};
+
+pub struct LetEnv;
+
+impl Command for LetEnv {
+    fn name(&self) -> &str {
+        "let-env"
+    }
+
+    fn usage(&self) -> &str {
+        "Create an environment variable and give it a value."
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("let-env")
+            .required("var_name", SyntaxShape::String, "variable name")
+            .required(
+                "initial_value",
+                SyntaxShape::Keyword(b"=".to_vec(), Box::new(SyntaxShape::String)),
+                "equals sign followed by value",
+            )
+    }
+
+    fn run(
+        &self,
+        context: &EvaluationContext,
+        call: &Call,
+        _input: Value,
+    ) -> Result<nu_protocol::Value, nu_protocol::ShellError> {
+        let env_var = call.positional[0]
+            .as_string()
+            .expect("internal error: missing variable");
+
+        let keyword_expr = call.positional[1]
+            .as_keyword()
+            .expect("internal error: missing keyword");
+
+        let rhs = eval_expression(context, keyword_expr)?;
+        let rhs = rhs.as_string()?;
+
+        //println!("Adding: {:?} to {}", rhs, var_id);
+
+        context.add_env_var(env_var, rhs);
+        Ok(Value::Nothing {
+            span: call.positional[0].span,
+        })
+    }
+}

crates/nu-command/src/lib.rs

@@ -1,7 +1,19 @@
-#[cfg(test)]
-mod tests {
-    #[test]
-    fn it_works() {
-        assert_eq!(2 + 2, 4);
-    }
-}
+mod alias;
+mod benchmark;
+mod build_string;
+mod def;
+mod default_context;
+mod for_;
+mod if_;
+mod let_;
+mod let_env;
+
+pub use alias::Alias;
+pub use benchmark::Benchmark;
+pub use build_string::BuildString;
+pub use def::Def;
+pub use default_context::create_default_context;
+pub use for_::For;
+pub use if_::If;
+pub use let_::Let;
+pub use let_env::LetEnv;

crates/nu-engine/src/eval.rs

@@ -1,5 +1,3 @@
-use std::time::Instant;
-
 use nu_protocol::ast::{Block, Call, Expr, Expression, Operator, Statement};
 use nu_protocol::engine::EvaluationContext;
 use nu_protocol::{IntoRowStream, IntoValueStream, ShellError, Span, Value};
@@ -14,11 +12,11 @@ pub fn eval_operator(op: &Expression) -> Result<Operator, ShellError> {
     }
 }
 
-fn eval_call(state: &EvaluationContext, call: &Call) -> Result<Value, ShellError> {
-    let engine_state = state.engine_state.borrow();
+fn eval_call(context: &EvaluationContext, call: &Call) -> Result<Value, ShellError> {
+    let engine_state = context.engine_state.borrow();
     let decl = engine_state.get_decl(call.decl_id);
     if let Some(block_id) = decl.get_custom_command() {
-        let state = state.enter_scope();
+        let state = context.enter_scope();
         for (arg, param) in call.positional.iter().zip(
             decl.signature()
                 .required_positional
@@ -35,158 +33,21 @@ fn eval_call(state: &EvaluationContext, call: &Call) -> Result<Value, ShellError
         let engine_state = state.engine_state.borrow();
         let block = engine_state.get_block(block_id);
         eval_block(&state, block)
-    } else if decl.signature().name == "let" {
-        let var_id = call.positional[0]
-            .as_var()
-            .expect("internal error: missing variable");
-
-        let keyword_expr = call.positional[1]
-            .as_keyword()
-            .expect("internal error: missing keyword");
-
-        let rhs = eval_expression(state, keyword_expr)?;
-
-        //println!("Adding: {:?} to {}", rhs, var_id);
-
-        state.add_var(var_id, rhs);
-        Ok(Value::Nothing {
-            span: call.positional[0].span,
-        })
-    } else if decl.signature().name == "let-env" {
-        let env_var = call.positional[0]
-            .as_string()
-            .expect("internal error: missing variable");
-
-        let keyword_expr = call.positional[1]
-            .as_keyword()
-            .expect("internal error: missing keyword");
-
-        let rhs = eval_expression(state, keyword_expr)?;
-        let rhs = rhs.as_string()?;
-
-        //println!("Adding: {:?} to {}", rhs, var_id);
-
-        state.add_env_var(env_var, rhs);
-        Ok(Value::Nothing {
-            span: call.positional[0].span,
-        })
-    } else if decl.signature().name == "if" {
-        let cond = &call.positional[0];
-        let then_block = call.positional[1]
-            .as_block()
-            .expect("internal error: expected block");
-        let else_case = call.positional.get(2);
-
-        let result = eval_expression(state, cond)?;
-        match result {
-            Value::Bool { val, span } => {
-                let engine_state = state.engine_state.borrow();
-                if val {
-                    let block = engine_state.get_block(then_block);
-                    let state = state.enter_scope();
-                    eval_block(&state, block)
-                } else if let Some(else_case) = else_case {
-                    if let Some(else_expr) = else_case.as_keyword() {
-                        if let Some(block_id) = else_expr.as_block() {
-                            let block = engine_state.get_block(block_id);
-                            let state = state.enter_scope();
-                            eval_block(&state, block)
-                        } else {
-                            eval_expression(state, else_expr)
-                        }
-                    } else {
-                        eval_expression(state, else_case)
-                    }
-                } else {
-                    Ok(Value::Nothing { span })
-                }
-            }
-            _ => Err(ShellError::CantConvert("bool".into(), result.span())),
-        }
-    } else if decl.signature().name == "build-string" {
-        let mut output = vec![];
-
-        for expr in &call.positional {
-            let val = eval_expression(state, expr)?;
-
-            output.push(val.into_string());
-        }
-        Ok(Value::String {
-            val: output.join(""),
-            span: call.head,
-        })
-    } else if decl.signature().name == "benchmark" {
-        let block = call.positional[0]
-            .as_block()
-            .expect("internal error: expected block");
-        let engine_state = state.engine_state.borrow();
-        let block = engine_state.get_block(block);
-
-        let state = state.enter_scope();
-        let start_time = Instant::now();
-        eval_block(&state, block)?;
-        let end_time = Instant::now();
-        println!("{} ms", (end_time - start_time).as_millis());
-        Ok(Value::Nothing {
-            span: call.positional[0].span,
-        })
-    } else if decl.signature().name == "for" {
-        let var_id = call.positional[0]
-            .as_var()
-            .expect("internal error: missing variable");
-
-        let keyword_expr = call.positional[1]
-            .as_keyword()
-            .expect("internal error: missing keyword");
-        let end_val = eval_expression(state, keyword_expr)?;
-
-        let block = call.positional[2]
-            .as_block()
-            .expect("internal error: expected block");
-        let engine_state = state.engine_state.borrow();
-        let block = engine_state.get_block(block);
-
-        let state = state.enter_scope();
-
-        let mut x = Value::Int {
-            val: 0,
-            span: Span::unknown(),
-        };
-
-        loop {
-            if x == end_val {
-                break;
-            } else {
-                state.add_var(var_id, x.clone());
-                eval_block(&state, block)?;
-            }
-            if let Value::Int { ref mut val, .. } = x {
-                *val += 1
-            }
-        }
-        Ok(Value::Nothing {
-            span: call.positional[0].span,
-        })
-    } else if decl.signature().name == "vars" {
-        state.engine_state.borrow().print_vars();
-        Ok(Value::Nothing { span: call.head })
-    } else if decl.signature().name == "decls" {
-        state.engine_state.borrow().print_decls();
-        Ok(Value::Nothing { span: call.head })
-    } else if decl.signature().name == "blocks" {
-        state.engine_state.borrow().print_blocks();
-        Ok(Value::Nothing { span: call.head })
-    } else if decl.signature().name == "stack" {
-        state.print_stack();
-        Ok(Value::Nothing { span: call.head })
-    } else if decl.signature().name == "def" || decl.signature().name == "alias" {
-        Ok(Value::Nothing { span: call.head })
     } else {
-        Err(ShellError::Unsupported(call.head))
+        decl.run(
+            context,
+            call,
+            Value::Nothing {
+                span: Span::unknown(),
+            },
+        )
     }
 }
 
-pub fn eval_expression(state: &EvaluationContext, expr: &Expression) -> Result<Value, ShellError> {
+pub fn eval_expression(
+    context: &EvaluationContext,
+    expr: &Expression,
+) -> Result<Value, ShellError> {
     match &expr.expr {
         Expr::Bool(b) => Ok(Value::Bool {
             val: *b,
@@ -200,17 +61,17 @@ pub fn eval_expression(state: &EvaluationContext, expr: &Expression) -> Result<V
             val: *f,
             span: expr.span,
         }),
-        Expr::Var(var_id) => state
+        Expr::Var(var_id) => context
             .get_var(*var_id)
             .map_err(move |_| ShellError::VariableNotFound(expr.span)),
-        Expr::Call(call) => eval_call(state, call),
+        Expr::Call(call) => eval_call(context, call),
         Expr::ExternalCall(_, _) => Err(ShellError::Unsupported(expr.span)),
         Expr::Operator(_) => Ok(Value::Nothing { span: expr.span }),
         Expr::BinaryOp(lhs, op, rhs) => {
             let op_span = op.span;
-            let lhs = eval_expression(state, lhs)?;
+            let lhs = eval_expression(context, lhs)?;
             let op = eval_operator(op)?;
-            let rhs = eval_expression(state, rhs)?;
+            let rhs = eval_expression(context, rhs)?;
 
             match op {
                 Operator::Plus => lhs.add(op_span, &rhs),
@@ -228,10 +89,10 @@ pub fn eval_expression(state: &EvaluationContext, expr: &Expression) -> Result<V
         }
 
         Expr::Subexpression(block_id) => {
-            let engine_state = state.engine_state.borrow();
+            let engine_state = context.engine_state.borrow();
             let block = engine_state.get_block(*block_id);
 
-            let state = state.enter_scope();
+            let state = context.enter_scope();
             eval_block(&state, block)
         }
         Expr::Block(block_id) => Ok(Value::Block {
@@ -241,7 +102,7 @@ pub fn eval_expression(state: &EvaluationContext, expr: &Expression) -> Result<V
         Expr::List(x) => {
             let mut output = vec![];
             for expr in x {
-                output.push(eval_expression(state, expr)?);
+                output.push(eval_expression(context, expr)?);
             }
             Ok(Value::List {
                 val: output.into_value_stream(),
@@ -251,14 +112,14 @@ pub fn eval_expression(state: &EvaluationContext, expr: &Expression) -> Result<V
         Expr::Table(headers, vals) => {
             let mut output_headers = vec![];
             for expr in headers {
-                output_headers.push(eval_expression(state, expr)?.as_string()?);
+                output_headers.push(eval_expression(context, expr)?.as_string()?);
             }
 
             let mut output_rows = vec![];
             for val in vals {
                 let mut row = vec![];
                 for expr in val {
-                    row.push(eval_expression(state, expr)?);
+                    row.push(eval_expression(context, expr)?);
                 }
                 output_rows.push(row);
             }
@@ -268,7 +129,7 @@ pub fn eval_expression(state: &EvaluationContext, expr: &Expression) -> Result<V
                 span: expr.span,
             })
         }
-        Expr::Keyword(_, _, expr) => eval_expression(state, expr),
+        Expr::Keyword(_, _, expr) => eval_expression(context, expr),
         Expr::String(s) => Ok(Value::String {
             val: s.clone(),
             span: expr.span,

crates/nu-parser/src/errors.rs

@@ -1,5 +1,4 @@
-use nu_protocol::{engine::StateWorkingSet, Span, Type};
-use std::ops::Range;
+use nu_protocol::{Span, Type};
 
 #[derive(Debug)]
 pub enum ParseError {

crates/nu-parser/src/parser.rs

@@ -7,7 +7,7 @@ use crate::{
 use nu_protocol::{
     ast::{Block, Call, Expr, Expression, Operator, Pipeline, Statement},
     engine::StateWorkingSet,
-    span, BlockId, DeclId, Flag, PositionalArg, Signature, Span, SyntaxShape, Type, VarId,
+    span, Flag, PositionalArg, Signature, Span, SyntaxShape, Type, VarId,
 };
 
 #[derive(Debug, Clone)]
@@ -416,9 +416,6 @@ pub fn parse_internal_call(
 
         // Parse a positional arg if there is one
         if let Some(positional) = signature.get_positional(positional_idx) {
-            //Make sure we leave enough spans for the remaining positionals
-            let decl = working_set.get_decl(decl_id);
-
             let end = calculate_end_span(working_set, &signature, spans, spans_idx, positional_idx);
 
             // println!(

crates/nu-protocol/src/engine/command.rs

@@ -1,6 +1,6 @@
-use crate::{BlockId, Example, ShellError, Signature, Value};
+use crate::{ast::Call, BlockId, Example, ShellError, Signature, Value};
 
-use super::CommandArgs;
+use super::EvaluationContext;
 
 pub trait Command {
     fn name(&self) -> &str;
@@ -15,19 +15,12 @@ pub trait Command {
         ""
     }
 
-    fn run(&self, args: CommandArgs) -> Result<Value, ShellError>;
-
-    // fn run(&self, args: CommandArgs) -> Result<InputStream, ShellError> {
-    //     let context = args.context.clone();
-    //     let stream = self.run_with_actions(args)?;
-
-    //     Ok(Box::new(crate::evaluate::internal::InternalIterator {
-    //         context,
-    //         input: stream,
-    //         leftovers: InputStream::empty(),
-    //     })
-    //     .into_output_stream())
-    // }
+    fn run(
+        &self,
+        context: &EvaluationContext,
+        call: &Call,
+        input: Value,
+    ) -> Result<Value, ShellError>;
 
     fn is_binary(&self) -> bool {
         false

crates/nu-protocol/src/engine/command_args.rs

@@ -1,7 +0,0 @@
-use super::{EvaluationContext, UnevaluatedCallInfo};
-
-pub struct CommandArgs {
-    pub context: EvaluationContext,
-    pub call_info: UnevaluatedCallInfo,
-    pub input: crate::Value,
-}

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

@@ -1,11 +1,9 @@
 mod call_info;
 mod command;
-mod command_args;
 mod engine_state;
 mod evaluation_context;
 
 pub use call_info::*;
 pub use command::*;
-pub use command_args::*;
 pub use engine_state::*;
 pub use evaluation_context::*;

crates/nu-protocol/src/signature.rs

@@ -1,6 +1,9 @@
+use crate::ast::Call;
 use crate::engine::Command;
+use crate::engine::EvaluationContext;
 use crate::BlockId;
 use crate::SyntaxShape;
+use crate::Value;
 use crate::VarId;
 
 #[derive(Debug, Clone)]
@@ -315,7 +318,12 @@ impl Command for Predeclaration {
         &self.signature.usage
     }
 
-    fn run(&self, _args: crate::engine::CommandArgs) -> Result<crate::Value, crate::ShellError> {
+    fn run(
+        &self,
+        _context: &EvaluationContext,
+        _call: &Call,
+        _input: Value,
+    ) -> Result<crate::Value, crate::ShellError> {
         panic!("Internal error: can't run a predeclaration without a body")
     }
 }
@@ -338,7 +346,12 @@ impl Command for BlockCommand {
         &self.signature.usage
     }
 
-    fn run(&self, _args: crate::engine::CommandArgs) -> Result<crate::Value, crate::ShellError> {
+    fn run(
+        &self,
+        _context: &EvaluationContext,
+        _call: &Call,
+        _input: Value,
+    ) -> Result<crate::Value, crate::ShellError> {
         panic!("Internal error: can't run custom command with 'run', use block_id");
     }
 

src/main.rs

@@ -1,4 +1,5 @@
-use nu_cli::{create_default_context, report_parsing_error, report_shell_error, NuHighlighter};
+use nu_cli::{report_parsing_error, report_shell_error, NuHighlighter};
+use nu_command::create_default_context;
 use nu_engine::eval_block;
 use nu_parser::parse_file;
 use nu_protocol::engine::{EngineState, EvaluationContext, StateWorkingSet};
@@ -68,8 +69,19 @@ fn main() -> std::io::Result<()> {
                 Ok(Signal::Success(s)) => {
                     if s.trim() == "exit" {
                         break;
+                    } else if s.trim() == "vars" {
+                        engine_state.borrow().print_vars();
+                        continue;
+                    } else if s.trim() == "decls" {
+                        engine_state.borrow().print_decls();
+                        continue;
+                    } else if s.trim() == "blocks" {
+                        engine_state.borrow().print_blocks();
+                        continue;
+                    } else if s.trim() == "stack" {
+                        stack.print_stack();
+                        continue;
                     }
-                    // println!("input: '{}'", s);
 
                     let (block, delta) = {
                         let engine_state = engine_state.borrow();