Allow arbitrary expressions as default arguments (#400)

GRAMMAR.md

@@ -63,6 +63,7 @@ value         : NAME '(' arguments? ')'
               | RAW_STRING
               | BACKTICK
               | NAME
+              | '(' expression ')'
 
 arguments     : expression ',' arguments
               | expression ','?
@@ -70,8 +71,7 @@ arguments     : expression ',' arguments
 recipe        : '@'? NAME parameter* ('+' parameter)? ':' dependencies? body?
 
 parameter     : NAME
-              | NAME '=' STRING
+              | NAME '=' value
-              | NAME '=' RAW_STRING
 
 dependencies  : NAME+
 

README.adoc

@@ -480,7 +480,9 @@ cd my-awesome-project && make
 Parameters may have default values:
 
 ```make
-test target tests='all':
+default = 'all'
+
+test target tests=default:
     @echo 'Testing {{target}}:{{tests}}...'
     ./test --tests {{tests}} {{target}}
 ```
@@ -501,6 +503,15 @@ Testing server:unit...
 ./test --tests unit server
 ```
 
+Default values may be arbitrary expressions, but concatenations must be parenthesized:
+
+```make
+arch = "wasm"
+
+test triple=(arch + "-unknown-unknown"):
+  ./test {{triple}}
+```
+
 The last parameter of a recipe may be variadic, indicated with a `+` before the argument name:
 
 ```make

src/alias.rs

@@ -1,5 +1,6 @@
 use crate::common::*;
 
+#[derive(Debug)]
 pub struct Alias<'a> {
   pub name: &'a str,
   pub target: &'a str,

src/assignment_evaluator.rs

@@ -83,7 +83,7 @@ impl<'a, 'b> AssignmentEvaluator<'a, 'b> {
     Ok(())
   }
 
-  fn evaluate_expression(
+  pub fn evaluate_expression(
     &mut self,
     expression: &Expression<'a>,
     arguments: &BTreeMap<&str, Cow<str>>,
@@ -120,7 +120,7 @@ impl<'a, 'b> AssignmentEvaluator<'a, 'b> {
         };
         evaluate_function(token, name, &context, &call_arguments)
       }
-      Expression::String { ref cooked_string } => Ok(cooked_string.cooked.clone()),
+      Expression::String { ref cooked_string } => Ok(cooked_string.cooked.to_string()),
       Expression::Backtick { raw, ref token } => {
         if self.dry_run {
           Ok(format!("`{}`", raw))
@@ -131,6 +131,7 @@ impl<'a, 'b> AssignmentEvaluator<'a, 'b> {
       Expression::Concatination { ref lhs, ref rhs } => {
         Ok(self.evaluate_expression(lhs, arguments)? + &self.evaluate_expression(rhs, arguments)?)
       }
+      Expression::Group { ref expression } => self.evaluate_expression(&expression, arguments),
     }
   }
 

src/assignment_resolver.rs

@@ -56,7 +56,7 @@ impl<'a: 'b, 'b> AssignmentResolver<'a, 'b> {
   }
 
   fn resolve_expression(&mut self, expression: &Expression<'a>) -> CompilationResult<'a, ()> {
-    match *expression {
+    match expression {
       Expression::Variable { name, ref token } => {
         if self.evaluated.contains(name) {
           return Ok(());
@@ -83,6 +83,7 @@ impl<'a: 'b, 'b> AssignmentResolver<'a, 'b> {
         self.resolve_expression(rhs)?;
       }
       Expression::String { .. } | Expression::Backtick { .. } => {}
+      Expression::Group { expression } => self.resolve_expression(expression)?,
     }
     Ok(())
   }

src/cooked_string.rs

@@ -3,7 +3,7 @@ use crate::common::*;
 #[derive(PartialEq, Debug)]
 pub struct CookedString<'a> {
   pub raw: &'a str,
-  pub cooked: String,
+  pub cooked: Cow<'a, str>,
 }
 
 impl<'a> CookedString<'a> {
@@ -12,7 +12,7 @@ impl<'a> CookedString<'a> {
 
     if let TokenKind::RawString = token.kind {
       Ok(CookedString {
-        cooked: raw.to_string(),
+        cooked: Cow::Borrowed(raw),
         raw,
       })
     } else if let TokenKind::StringToken = token.kind {
@@ -41,7 +41,10 @@ impl<'a> CookedString<'a> {
         }
         cooked.push(c);
       }
-      Ok(CookedString { raw, cooked })
+      Ok(CookedString {
+        raw,
+        cooked: Cow::Owned(cooked),
+      })
     } else {
       Err(token.error(CompilationErrorKind::Internal {
         message: "cook_string() called on non-string token".to_string(),
@@ -49,3 +52,12 @@ impl<'a> CookedString<'a> {
     }
   }
 }
+
+impl<'a> Display for CookedString<'a> {
+  fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+    match self.cooked {
+      Cow::Borrowed(raw) => write!(f, "'{}'", raw),
+      Cow::Owned(_) => write!(f, "\"{}\"", self.raw),
+    }
+  }
+}

src/expression.rs

@@ -22,6 +22,9 @@ pub enum Expression<'a> {
     name: &'a str,
     token: Token<'a>,
   },
+  Group {
+    expression: Box<Expression<'a>>,
+  },
 }
 
 impl<'a> Expression<'a> {
@@ -39,7 +42,7 @@ impl<'a> Display for Expression<'a> {
     match *self {
       Expression::Backtick { raw, .. } => write!(f, "`{}`", raw)?,
       Expression::Concatination { ref lhs, ref rhs } => write!(f, "{} + {}", lhs, rhs)?,
-      Expression::String { ref cooked_string } => write!(f, "\"{}\"", cooked_string.raw)?,
+      Expression::String { ref cooked_string } => write!(f, "{}", cooked_string)?,
       Expression::Variable { name, .. } => write!(f, "{}", name)?,
       Expression::Call {
         name,
@@ -56,6 +59,7 @@ impl<'a> Display for Expression<'a> {
         }
         write!(f, ")")?;
       }
+      Expression::Group { ref expression } => write!(f, "({})", expression)?,
     }
     Ok(())
   }
@@ -71,15 +75,19 @@ impl<'a> Iterator for Variables<'a> {
   fn next(&mut self) -> Option<&'a Token<'a>> {
     match self.stack.pop() {
       None
-      | Some(&Expression::String { .. })
+      | Some(Expression::String { .. })
-      | Some(&Expression::Backtick { .. })
+      | Some(Expression::Backtick { .. })
-      | Some(&Expression::Call { .. }) => None,
+      | Some(Expression::Call { .. }) => None,
-      Some(&Expression::Variable { ref token, .. }) => Some(token),
+      Some(Expression::Variable { token, .. }) => Some(token),
-      Some(&Expression::Concatination { ref lhs, ref rhs }) => {
+      Some(Expression::Concatination { lhs, rhs }) => {
         self.stack.push(lhs);
         self.stack.push(rhs);
         self.next()
       }
+      Some(Expression::Group { expression }) => {
+        self.stack.push(expression);
+        self.next()
+      }
     }
   }
 }
@@ -94,19 +102,21 @@ impl<'a> Iterator for Functions<'a> {
   fn next(&mut self) -> Option<Self::Item> {
     match self.stack.pop() {
       None
-      | Some(&Expression::String { .. })
+      | Some(Expression::String { .. })
-      | Some(&Expression::Backtick { .. })
+      | Some(Expression::Backtick { .. })
-      | Some(&Expression::Variable { .. }) => None,
+      | Some(Expression::Variable { .. }) => None,
-      Some(&Expression::Call {
+      Some(Expression::Call {
-        ref token,
+        token, arguments, ..
-        ref arguments,
-        ..
       }) => Some((token, arguments.len())),
-      Some(&Expression::Concatination { ref lhs, ref rhs }) => {
+      Some(Expression::Concatination { lhs, rhs }) => {
         self.stack.push(lhs);
         self.stack.push(rhs);
         self.next()
       }
+      Some(Expression::Group { expression }) => {
+        self.stack.push(expression);
+        self.next()
+      }
     }
   }
 }

src/justfile.rs

@@ -1,5 +1,6 @@
 use crate::common::*;
 
+#[derive(Debug)]
 pub struct Justfile<'a> {
   pub recipes: BTreeMap<&'a str, Recipe<'a>>,
   pub assignments: BTreeMap<&'a str, Expression<'a>>,

src/lexer.rs

@@ -617,6 +617,12 @@ c: b
     "#$#$.",
   }
 
+  summary_test! {
+    multiple_recipes,
+    "a:\n  foo\nb:",
+    "N:$>^_$<N:.",
+  }
+
   error_test! {
     name:  tokenize_space_then_tab,
     input: "a:

src/parameter.rs

@@ -2,7 +2,7 @@ use crate::common::*;
 
 #[derive(PartialEq, Debug)]
 pub struct Parameter<'a> {
-  pub default: Option<String>,
+  pub default: Option<Expression<'a>>,
   pub name: &'a str,
   pub token: Token<'a>,
   pub variadic: bool,
@@ -16,11 +16,7 @@ impl<'a> Display for Parameter<'a> {
     }
     write!(f, "{}", color.parameter().paint(self.name))?;
     if let Some(ref default) = self.default {
-      let escaped = default
+      write!(f, "={}", color.string().paint(&default.to_string()))?;
-        .chars()
-        .flat_map(char::escape_default)
-        .collect::<String>();;
-      write!(f, r#"='{}'"#, color.string().paint(&escaped))?;
     }
     Ok(())
   }

src/parser.rs

@@ -49,15 +49,6 @@ impl<'a> Parser<'a> {
     }
   }
 
-  fn accept_any(&mut self, kinds: &[TokenKind]) -> Option<Token<'a>> {
-    for kind in kinds {
-      if self.peek(*kind) {
-        return self.tokens.next();
-      }
-    }
-    None
-  }
-
   fn accepted(&mut self, kind: TokenKind) -> bool {
     self.accept(kind).is_some()
   }
@@ -137,12 +128,7 @@ impl<'a> Parser<'a> {
 
       let default;
       if self.accepted(Equals) {
-        if let Some(string) = self.accept_any(&[StringToken, RawString]) {
+        default = Some(self.value()?);
-          default = Some(CookedString::new(&string)?.cooked);
-        } else {
-          let unexpected = self.tokens.next().unwrap();
-          return Err(self.unexpected_token(&unexpected, &[StringToken, RawString]));
-        }
       } else {
         default = None
       }
@@ -243,6 +229,10 @@ impl<'a> Parser<'a> {
       }
     }
 
+    while lines.last().map(Vec::is_empty).unwrap_or(false) {
+      lines.pop();
+    }
+
     self.recipes.insert(
       name.lexeme,
       Recipe {
@@ -262,9 +252,10 @@ impl<'a> Parser<'a> {
     Ok(())
   }
 
-  fn expression(&mut self) -> CompilationResult<'a, Expression<'a>> {
+  fn value(&mut self) -> CompilationResult<'a, Expression<'a>> {
     let first = self.tokens.next().unwrap();
-    let lhs = match first.kind {
+
+    match first.kind {
       Name => {
         if self.peek(ParenL) {
           if let Some(token) = self.expect(ParenL) {
@@ -274,30 +265,46 @@ impl<'a> Parser<'a> {
           if let Some(token) = self.expect(ParenR) {
             return Err(self.unexpected_token(&token, &[Name, StringToken, ParenR]));
           }
-          Expression::Call {
+          Ok(Expression::Call {
             name: first.lexeme,
             token: first,
             arguments,
-          }
+          })
         } else {
-          Expression::Variable {
+          Ok(Expression::Variable {
             name: first.lexeme,
             token: first,
-          }
+          })
         }
       }
-      Backtick => Expression::Backtick {
+      Backtick => Ok(Expression::Backtick {
         raw: &first.lexeme[1..first.lexeme.len() - 1],
         token: first,
-      },
+      }),
-      RawString | StringToken => Expression::String {
+      RawString | StringToken => Ok(Expression::String {
         cooked_string: CookedString::new(&first)?,
-      },
+      }),
-      _ => return Err(self.unexpected_token(&first, &[Name, StringToken])),
+      ParenL => {
-    };
+        let expression = self.expression()?;
+
+        if let Some(token) = self.expect(ParenR) {
+          return Err(self.unexpected_token(&token, &[ParenR]));
+        }
+
+        Ok(Expression::Group {
+          expression: Box::new(expression),
+        })
+      }
+      _ => Err(self.unexpected_token(&first, &[Name, StringToken])),
+    }
+  }
+
+  fn expression(&mut self) -> CompilationResult<'a, Expression<'a>> {
+    let lhs = self.value()?;
 
     if self.accepted(Plus) {
       let rhs = self.expression()?;
+
       Ok(Expression::Concatination {
         lhs: Box::new(lhs),
         rhs: Box::new(rhs),
@@ -463,6 +470,8 @@ impl<'a> Parser<'a> {
       }));
     }
 
+    AssignmentResolver::resolve_assignments(&self.assignments, &self.assignment_tokens)?;
+
     RecipeResolver::resolve_recipes(&self.recipes, &self.assignments, self.text)?;
 
     for recipe in self.recipes.values() {
@@ -486,8 +495,6 @@ impl<'a> Parser<'a> {
 
     AliasResolver::resolve_aliases(&self.aliases, &self.recipes, &self.alias_tokens)?;
 
-    AssignmentResolver::resolve_assignments(&self.assignments, &self.assignment_tokens)?;
-
     Ok(Justfile {
       recipes: self.recipes,
       assignments: self.assignments,
@@ -513,9 +520,17 @@ mod test {
         let actual = format!("{:#}", justfile);
         if actual != expected {
           println!("got:\n\"{}\"\n", actual);
-          println!("\texpected:\n\"{}\"", expected);
+          println!("expected:\n\"{}\"", expected);
           assert_eq!(actual, expected);
         }
+        println!("Re-parsing...");
+        let reparsed = parse_success(&actual);
+        let redumped = format!("{:#}", reparsed);
+        if redumped != actual {
+          println!("reparsed:\n\"{}\"\n", redumped);
+          println!("expected:\n\"{}\"", actual);
+          assert_eq!(redumped, actual);
+        }
       }
     };
   }
@@ -539,7 +554,18 @@ foo a="b\t":
 
 
   "#,
-    r#"foo a='b\t':"#,
+    r#"foo a="b\t":"#,
+  }
+
+  summary_test! {
+  parse_multiple,
+    r#"
+a:
+b:
+"#,
+    r#"a:
+
+b:"#,
   }
 
   summary_test! {
@@ -561,7 +587,7 @@ foo +a="Hello":
 
 
   "#,
-    r#"foo +a='Hello':"#,
+    r#"foo +a="Hello":"#,
   }
 
   summary_test! {
@@ -572,7 +598,7 @@ foo a='b\t':
 
 
   "#,
-    r#"foo a='b\\t':"#,
+    r#"foo a='b\t':"#,
   }
 
   summary_test! {
@@ -671,7 +697,7 @@ install:
 \t\treturn
 \tfi
 ",
-    "practicum = \"hello\"
+    "practicum = 'hello'
 
 install:
     #!/bin/sh
@@ -765,10 +791,76 @@ x = env_var('foo',)
 
 a:
   {{env_var_or_default('foo' + 'bar', 'baz',)}} {{env_var(env_var("baz"))}}"#,
-    r#"x = env_var("foo")
+    r#"x = env_var('foo')
 
 a:
-    {{env_var_or_default("foo" + "bar", "baz")}} {{env_var(env_var("baz"))}}"#,
+    {{env_var_or_default('foo' + 'bar', 'baz')}} {{env_var(env_var("baz"))}}"#,
+  }
+
+  summary_test! {
+    parameter_default_string,
+    r#"
+f x="abc":
+"#,
+    r#"f x="abc":"#,
+  }
+
+  summary_test! {
+    parameter_default_raw_string,
+    r#"
+f x='abc':
+"#,
+    r#"f x='abc':"#,
+  }
+
+  summary_test! {
+    parameter_default_backtick,
+    r#"
+f x=`echo hello`:
+"#,
+    r#"f x=`echo hello`:"#,
+  }
+
+  summary_test! {
+    parameter_default_concatination_string,
+    r#"
+f x=(`echo hello` + "foo"):
+"#,
+    r#"f x=(`echo hello` + "foo"):"#,
+  }
+
+  summary_test! {
+    parameter_default_concatination_variable,
+    r#"
+x = "10"
+f y=(`echo hello` + x) +z="foo":
+"#,
+    r#"x = "10"
+
+f y=(`echo hello` + x) +z="foo":"#,
+  }
+
+  summary_test! {
+    parameter_default_multiple,
+    r#"
+x = "10"
+f y=(`echo hello` + x) +z=("foo" + "bar"):
+"#,
+    r#"x = "10"
+
+f y=(`echo hello` + x) +z=("foo" + "bar"):"#,
+  }
+
+  summary_test! {
+    concatination_in_group,
+    "x = ('0' + '1')",
+    "x = ('0' + '1')",
+  }
+
+  summary_test! {
+    string_in_group,
+    "x = ('0'   )",
+    "x = ('0')",
   }
 
   compilation_error_test! {
@@ -848,7 +940,7 @@ a:
     line:   0,
     column: 10,
     width:  Some(1),
-    kind:   UnexpectedToken{expected: vec![StringToken, RawString], found: Eol},
+    kind:   UnexpectedToken{expected: vec![Name, StringToken], found: Eol},
   }
 
   compilation_error_test! {
@@ -858,27 +950,7 @@ a:
     line:   0,
     column: 10,
     width:  Some(0),
-    kind:   UnexpectedToken{expected: vec![StringToken, RawString], found: Eof},
+    kind:   UnexpectedToken{expected: vec![Name, StringToken], found: Eof},
-  }
-
-  compilation_error_test! {
-    name:   missing_default_colon,
-    input:  "hello arg=:",
-    index:  10,
-    line:   0,
-    column: 10,
-    width:  Some(1),
-    kind:   UnexpectedToken{expected: vec![StringToken, RawString], found: Colon},
-  }
-
-  compilation_error_test! {
-    name:   missing_default_backtick,
-    input:  "hello arg=`hello`",
-    index:  10,
-    line:   0,
-    column: 10,
-    width:  Some(7),
-    kind:   UnexpectedToken{expected: vec![StringToken, RawString], found: Backtick},
   }
 
   compilation_error_test! {
@@ -1065,4 +1137,33 @@ a:
       parse_success(&justfile);
     }
   }
+
+  #[test]
+  fn empty_recipe_lines() {
+    let text = "a:";
+    let justfile = parse_success(&text);
+
+    assert_eq!(justfile.recipes["a"].lines.len(), 0);
+  }
+
+  #[test]
+  fn simple_recipe_lines() {
+    let text = "a:\n foo";
+    let justfile = parse_success(&text);
+
+    assert_eq!(justfile.recipes["a"].lines.len(), 1);
+  }
+
+  #[test]
+  fn complex_recipe_lines() {
+    let text = "a:
+  foo
+
+b:
+";
+
+    let justfile = parse_success(&text);
+
+    assert_eq!(justfile.recipes["a"].lines.len(), 1);
+  }
 }

src/recipe.rs

@@ -86,11 +86,24 @@ impl<'a> Recipe<'a> {
 
     let mut argument_map = BTreeMap::new();
 
+    let mut evaluator = AssignmentEvaluator {
+      assignments: &empty(),
+      dry_run: configuration.dry_run,
+      evaluated: empty(),
+      invocation_directory: context.invocation_directory,
+      overrides: &empty(),
+      quiet: configuration.quiet,
+      scope: &context.scope,
+      shell: configuration.shell,
+      dotenv,
+      exports,
+    };
+
     let mut rest = arguments;
     for parameter in &self.parameters {
       let value = if rest.is_empty() {
         match parameter.default {
-          Some(ref default) => Cow::Borrowed(default.as_str()),
+          Some(ref default) => Cow::Owned(evaluator.evaluate_expression(default, &empty())?),
           None => {
             return Err(RuntimeError::Internal {
               message: "missing parameter without default".to_string(),
@@ -109,19 +122,6 @@ impl<'a> Recipe<'a> {
       argument_map.insert(parameter.name, value);
     }
 
-    let mut evaluator = AssignmentEvaluator {
-      assignments: &empty(),
-      dry_run: configuration.dry_run,
-      evaluated: empty(),
-      invocation_directory: context.invocation_directory,
-      overrides: &empty(),
-      quiet: configuration.quiet,
-      scope: &context.scope,
-      shell: configuration.shell,
-      dotenv,
-      exports,
-    };
-
     if self.shebang {
       let mut evaluated_lines = vec![];
       for line in &self.lines {

src/recipe_resolver.rs

@@ -2,11 +2,23 @@ use crate::common::*;
 
 use CompilationErrorKind::*;
 
+// There are borrow issues here that seems too difficult to solve.
+// The errors derived from the variable token has too short a lifetime,
+// so we create a new error from its contents, which do live long
+// enough.
+//
+// I suspect the solution here is to give recipes, pieces, and expressions
+// two lifetime parameters instead of one, with one being the lifetime
+// of the struct, and the second being the lifetime of the tokens
+// that it contains.
+
 pub struct RecipeResolver<'a: 'b, 'b> {
   stack: Vec<&'a str>,
   seen: BTreeSet<&'a str>,
   resolved: BTreeSet<&'a str>,
   recipes: &'b BTreeMap<&'a str, Recipe<'a>>,
+  assignments: &'b BTreeMap<&'a str, Expression<'a>>,
+  text: &'a str,
 }
 
 impl<'a, 'b> RecipeResolver<'a, 'b> {
@@ -19,6 +31,8 @@ impl<'a, 'b> RecipeResolver<'a, 'b> {
       seen: empty(),
       stack: empty(),
       resolved: empty(),
+      assignments,
+      text,
       recipes,
     };
 
@@ -27,51 +41,26 @@ impl<'a, 'b> RecipeResolver<'a, 'b> {
       resolver.seen = empty();
     }
 
-    // There are borrow issues here that seems too difficult to solve.
-    // The errors derived from the variable token has too short a lifetime,
-    // so we create a new error from its contents, which do live long
-    // enough.
-    //
-    // I suspect the solution here is to give recipes, pieces, and expressions
-    // two lifetime parameters instead of one, with one being the lifetime
-    // of the struct, and the second being the lifetime of the tokens
-    // that it contains.
-
     for recipe in recipes.values() {
+      for parameter in &recipe.parameters {
+        if let Some(expression) = &parameter.default {
+          for (function, argc) in expression.functions() {
+            resolver.resolve_function(function, argc)?;
+          }
+          for variable in expression.variables() {
+            resolver.resolve_variable(variable, &[])?;
+          }
+        }
+      }
+
       for line in &recipe.lines {
         for fragment in line {
           if let Fragment::Expression { ref expression, .. } = *fragment {
             for (function, argc) in expression.functions() {
-              if let Err(error) = resolve_function(function, argc) {
+              resolver.resolve_function(function, argc)?;
-                return Err(CompilationError {
-                  index: error.index,
-                  line: error.line,
-                  column: error.column,
-                  width: error.width,
-                  kind: UnknownFunction {
-                    function: &text[error.index..error.index + error.width.unwrap()],
-                  },
-                  text,
-                });
-              }
             }
             for variable in expression.variables() {
-              let name = variable.lexeme;
+              resolver.resolve_variable(variable, &recipe.parameters)?;
-              let undefined = !assignments.contains_key(name)
-                && !recipe.parameters.iter().any(|p| p.name == name);
-              if undefined {
-                let error = variable.error(UndefinedVariable { variable: name });
-                return Err(CompilationError {
-                  index: error.index,
-                  line: error.line,
-                  column: error.column,
-                  width: error.width,
-                  kind: UndefinedVariable {
-                    variable: &text[error.index..error.index + error.width.unwrap()],
-                  },
-                  text,
-                });
-              }
             }
           }
         }
@@ -81,6 +70,44 @@ impl<'a, 'b> RecipeResolver<'a, 'b> {
     Ok(())
   }
 
+  fn resolve_function(&self, function: &Token, argc: usize) -> CompilationResult<'a, ()> {
+    resolve_function(function, argc).map_err(|error| CompilationError {
+      index: error.index,
+      line: error.line,
+      column: error.column,
+      width: error.width,
+      kind: UnknownFunction {
+        function: &self.text[error.index..error.index + error.width.unwrap()],
+      },
+      text: self.text,
+    })
+  }
+
+  fn resolve_variable(
+    &self,
+    variable: &Token,
+    parameters: &[Parameter],
+  ) -> CompilationResult<'a, ()> {
+    let name = variable.lexeme;
+    let undefined =
+      !self.assignments.contains_key(name) && !parameters.iter().any(|p| p.name == name);
+    if undefined {
+      let error = variable.error(UndefinedVariable { variable: name });
+      return Err(CompilationError {
+        index: error.index,
+        line: error.line,
+        column: error.column,
+        width: error.width,
+        kind: UndefinedVariable {
+          variable: &self.text[error.index..error.index + error.width.unwrap()],
+        },
+        text: self.text,
+      });
+    }
+
+    Ok(())
+  }
+
   fn resolve_recipe(&mut self, recipe: &Recipe<'a>) -> CompilationResult<'a, ()> {
     if self.resolved.contains(recipe.name) {
       return Ok(());
@@ -186,4 +213,24 @@ mod test {
     width:  Some(3),
     kind:   UnknownFunction{function: "bar"},
   }
+
+  compilation_error_test! {
+    name:   unknown_function_in_default,
+    input:  "a f=baz():",
+    index:  4,
+    line:   0,
+    column: 4,
+    width:  Some(3),
+    kind:   UnknownFunction{function: "baz"},
+  }
+
+  compilation_error_test! {
+    name:   unknown_variable_in_default,
+    input:  "a f=foo:",
+    index:  4,
+    line:   0,
+    column: 4,
+    width:  Some(3),
+    kind:   UndefinedVariable{variable: "foo"},
+  }
 }

src/summary.rs

@@ -18,7 +18,7 @@ use std::{
   path::Path,
 };
 
-use crate::{expression, fragment, justfile::Justfile, parser::Parser, recipe};
+use crate::{expression, fragment, justfile::Justfile, parameter, parser::Parser, recipe};
 
 pub fn summary(path: impl AsRef<Path>) -> Result<Result<Summary, String>, io::Error> {
   let path = path.as_ref();
@@ -46,7 +46,7 @@ impl Summary {
     for alias in justfile.aliases.values() {
       aliases
         .entry(alias.target)
-        .or_insert(Vec::new())
+        .or_insert_with(Vec::new)
         .push(alias.name.to_string());
     }
 
@@ -57,7 +57,7 @@ impl Summary {
         .map(|(name, recipe)| {
           (
             name.to_string(),
-            Recipe::new(recipe, aliases.remove(name).unwrap_or(Vec::new())),
+            Recipe::new(recipe, aliases.remove(name).unwrap_or_default()),
           )
         })
         .collect(),
@@ -83,6 +83,7 @@ pub struct Recipe {
   pub private: bool,
   pub quiet: bool,
   pub shebang: bool,
+  pub parameters: Vec<Parameter>,
 }
 
 impl Recipe {
@@ -93,11 +94,31 @@ impl Recipe {
       quiet: recipe.quiet,
       dependencies: recipe.dependencies.into_iter().map(str::to_owned).collect(),
       lines: recipe.lines.into_iter().map(Line::new).collect(),
+      parameters: recipe.parameters.into_iter().map(Parameter::new).collect(),
       aliases,
     }
   }
 }
 
+#[derive(Eq, PartialEq, Hash, Ord, PartialOrd, Debug, Clone)]
+pub struct Parameter {
+  pub variadic: bool,
+  pub name: String,
+  pub default: Option<Expression>,
+}
+
+impl Parameter {
+  fn new(parameter: parameter::Parameter) -> Parameter {
+    Parameter {
+      variadic: parameter.variadic,
+      name: parameter.name.to_owned(),
+      default: parameter
+        .default
+        .map(|expression| Expression::new(expression)),
+    }
+  }
+}
+
 #[derive(Eq, PartialEq, Hash, Ord, PartialOrd, Debug, Clone)]
 pub struct Line {
   pub fragments: Vec<Fragment>,
@@ -184,11 +205,12 @@ impl Expression {
         rhs: Box::new(Expression::new(*rhs)),
       },
       String { cooked_string } => Expression::String {
-        text: cooked_string.cooked,
+        text: cooked_string.cooked.to_string(),
       },
       Variable { name, .. } => Expression::Variable {
         name: name.to_owned(),
       },
+      Group { expression } => Expression::new(*expression),
     }
   }
 }

tests/integration.rs

@@ -1,8 +1,6 @@
 use executable_path::executable_path;
 use libc::{EXIT_FAILURE, EXIT_SUCCESS};
-use std::env;
+use std::{env, fs, process, str};
-use std::process;
-use std::str;
 use tempdir::TempDir;
 
 /// Instantiate integration tests for a given test case using
@@ -93,6 +91,46 @@ fn integration_test(
   if failure {
     panic!("test failed");
   }
+
+  if expected_status == EXIT_SUCCESS {
+    println!("Reparsing...");
+
+    let output = process::Command::new(&executable_path("just"))
+      .current_dir(tmp.path())
+      .arg("--dump")
+      .output()
+      .expect("just invocation failed");
+
+    if !output.status.success() {
+      panic!("dump failed: {}", output.status);
+    }
+
+    let dumped = String::from_utf8(output.stdout).unwrap();
+
+    let reparsed_path = tmp.path().join("reparsed.just");
+
+    fs::write(&reparsed_path, &dumped).unwrap();
+
+    let output = process::Command::new(&executable_path("just"))
+      .current_dir(tmp.path())
+      .arg("--justfile")
+      .arg(&reparsed_path)
+      .arg("--dump")
+      .output()
+      .expect("just invocation failed");
+
+    if !output.status.success() {
+      panic!("reparse failed: {}", output.status);
+    }
+
+    let reparsed = String::from_utf8(output.stdout).unwrap();
+
+    if reparsed != dumped {
+      print!("expected:\n{}", reparsed);
+      print!("got:\n{}", dumped);
+      assert_eq!(reparsed, dumped);
+    }
+  }
 }
 
 integration_test! {
@@ -1115,10 +1153,10 @@ a Z="\t z":
 _private-recipe:
 "#,
   args:     ("--list"),
-  stdout:   r"Available recipes:
+  stdout:   r#"Available recipes:
-    a Z='\t z'
+    a Z="\t z"
-    hello a b='B\t' c='C' # this does a thing
+    hello a b='B	' c='C' # this does a thing
-",
+"#,
   stderr:   "",
   status:   EXIT_SUCCESS,
 }
@@ -1138,10 +1176,10 @@ a Z="\t z":
 _private-recipe:
 "#,
   args:     ("--list"),
-  stdout:   r"Available recipes:
+  stdout:   r#"Available recipes:
-    a Z='\t z'            # something else
+    a Z="\t z"          # something else
-    hello a b='B\t' c='C' # this does a thing
+    hello a b='B	' c='C' # this does a thing
-",
+"#,
   stderr:   "",
   status:   EXIT_SUCCESS,
 }
@@ -1165,11 +1203,11 @@ this-recipe-is-very-very-very-important Z="\t z":
 _private-recipe:
 "#,
   args:     ("--list"),
-  stdout:   r"Available recipes:
+  stdout:   r#"Available recipes:
-    hello a b='B\t' c='C' # this does a thing
+    hello a b='B	' c='C' # this does a thing
-    this-recipe-is-very-very-very-important Z='\t z' # something else
+    this-recipe-is-very-very-very-important Z="\t z" # something else
-    x a b='B\t' c='C'     # this does another thing
+    x a b='B	' c='C'     # this does another thing
-",
+"#,
   stderr:   "",
   status:   EXIT_SUCCESS,
 }
@@ -1386,8 +1424,6 @@ b
 
 
 c
-
-
 ",
   stderr:   "",
   status:   EXIT_SUCCESS,
@@ -1809,8 +1845,8 @@ a B C +D='hello':
   args:     ("--color", "always", "--list"),
   stdout:   "Available recipes:\n    a \
     \u{1b}[36mB\u{1b}[0m \u{1b}[36mC\u{1b}[0m \u{1b}[35m+\
-    \u{1b}[0m\u{1b}[36mD\u{1b}[0m=\'\u{1b}[32mhello\u{1b}[0m\
+    \u{1b}[0m\u{1b}[36mD\u{1b}[0m=\u{1b}[32m'hello'\u{1b}[0m \
-    \' \u{1b}[34m#\u{1b}[0m \u{1b}[34mcomment\u{1b}[0m\n",
+     \u{1b}[34m#\u{1b}[0m \u{1b}[34mcomment\u{1b}[0m\n",
   stderr:   "",
   status:   EXIT_SUCCESS,
 }
@@ -1924,3 +1960,94 @@ X = "\'"
 "#,
    status:   EXIT_FAILURE,
 }
+
+integration_test! {
+   name:     unknown_variable_in_default,
+   justfile: "
+foo x=bar:
+",
+   args:     (),
+   stdout:   "",
+   stderr:   r#"error: Variable `bar` not defined
+  |
+2 | foo x=bar:
+  |       ^^^
+"#,
+   status:   EXIT_FAILURE,
+}
+
+integration_test! {
+   name:     unknown_function_in_default,
+   justfile: "
+foo x=bar():
+",
+   args:     (),
+   stdout:   "",
+   stderr:   r#"error: Call to unknown function `bar`
+  |
+2 | foo x=bar():
+  |       ^^^
+"#,
+   status:   EXIT_FAILURE,
+}
+
+integration_test! {
+   name:     default_string,
+   justfile: "
+foo x='bar':
+  echo {{x}}
+",
+   args:     (),
+   stdout:   "bar\n",
+   stderr:   "echo bar\n",
+   status:   EXIT_SUCCESS,
+}
+
+integration_test! {
+   name:     default_concatination,
+   justfile: "
+foo x=(`echo foo` + 'bar'):
+  echo {{x}}
+",
+   args:     (),
+   stdout:   "foobar\n",
+   stderr:   "echo foobar\n",
+   status:   EXIT_SUCCESS,
+}
+
+integration_test! {
+   name:     default_backtick,
+   justfile: "
+foo x=`echo foo`:
+  echo {{x}}
+",
+   args:     (),
+   stdout:   "foo\n",
+   stderr:   "echo foo\n",
+   status:   EXIT_SUCCESS,
+}
+
+integration_test! {
+   name:     default_variable,
+   justfile: "
+y = 'foo'
+foo x=y:
+  echo {{x}}
+",
+   args:     (),
+   stdout:   "foo\n",
+   stderr:   "echo foo\n",
+   status:   EXIT_SUCCESS,
+}
+
+integration_test! {
+  name:     test_os_arch_functions_in_default,
+  justfile: r#"
+foo a=arch() o=os() f=os_family():
+  echo {{a}} {{o}} {{f}}
+"#,
+  args:     (),
+  stdout:   format!("{} {} {}\n", target::arch(), target::os(), target::os_family()).as_str(),
+  stderr:   format!("echo {} {} {}\n", target::arch(), target::os(), target::os_family()).as_str(),
+  status:   EXIT_SUCCESS,
+}

tests/interrupts.rs

@@ -1,7 +1,6 @@
 use executable_path::executable_path;
 use std::{
   process::Command,
-  thread,
   time::{Duration, Instant},
 };
 use tempdir::TempDir;
@@ -33,7 +32,7 @@ fn interrupt_test(justfile: &str) {
     .spawn()
     .expect("just invocation failed");
 
-  thread::sleep(Duration::new(1, 0));
+  while start.elapsed() < Duration::from_millis(500) {}
 
   kill(child.id());
 
@@ -41,11 +40,11 @@ fn interrupt_test(justfile: &str) {
 
   let elapsed = start.elapsed();
 
-  if elapsed > Duration::new(4, 0) {
+  if elapsed > Duration::from_secs(2) {
     panic!("process returned too late: {:?}", elapsed);
   }
 
-  if elapsed < Duration::new(1, 0) {
+  if elapsed < Duration::from_millis(100) {
     panic!("process returned too early : {:?}", elapsed);
   }
 
@@ -59,7 +58,7 @@ fn interrupt_shebang() {
     "
 default:
   #!/usr/bin/env sh
-  sleep 2
+  sleep 1
 ",
   );
 }
@@ -70,7 +69,7 @@ fn interrupt_line() {
   interrupt_test(
     "
 default:
-  @sleep 2
+  @sleep 1
 ",
   );
 }
@@ -80,7 +79,7 @@ default:
 fn interrupt_backtick() {
   interrupt_test(
     "
-foo = `sleep 2`
+foo = `sleep 1`
 
 default:
   @echo hello