Add variadic parameters (#127)

Recipes may now have a final variadic parameter:

```make
foo bar+:
  @echo {{bar}}
```

Variadic parameters accept one or more arguments, and expand to a string containing those arguments separated by spaces:

```sh
$ just foo a b c d e
a b c d e
```

I elected to accept one or more arguments instead of zero or more arguments since unexpectedly empty arguments can sometimes be dangerous. 

```make
clean dir:
  rm -rf {{dir}}/bin
```

If `dir` is empty in the above recipe, you'll delete `/bin`, which is probably not what was intended.

GRAMMAR.md

@@ -4,7 +4,7 @@ justfile grammar
 Justfiles are processed by a mildly context-sensitive tokenizer
 and a recursive descent parser. The grammar is mostly LL(1),
 although an extra token of lookahead is used to distinguish between
-export assignments and recipes with arguments.
+export assignments and recipes with parameters.
 
 tokens
 ------
@@ -51,9 +51,9 @@ expression    : STRING
               | BACKTICK
               | expression '+' expression
 
-recipe        : '@'? NAME argument* ':' dependencies? body?
+recipe        : '@'? NAME parameter* ('+' parameter)? ':' dependencies? body?
 
-argument      : NAME
+parameter     : NAME
               | NAME '=' STRING
               | NAME '=' RAW_STRING
 

README.md

@@ -264,6 +264,22 @@ Testing server:unit...
 ./test --tests unit server
 ```
 
+The last parameter to a recipe may be variadic, indicated with a `+` before the argument name:
+
+```make
+backup +FILES:
+  scp {{FILES}} me@server.com:
+```
+
+Variadic parameters accept one or more arguments and expand to a string containing those arguments separated by spaces:
+
+```sh
+$ just backup FAQ.md GRAMMAR.md
+scp FAQ.md GRAMMAR.md me@server.com:
+FAQ.md                  100% 1831     1.8KB/s   00:00
+GRAMMAR.md              100% 1666     1.6KB/s   00:00
+```
+
 Variables can be exported to recipes as environment variables:
 
 ```make

src/integration.rs

@@ -1038,16 +1038,16 @@ Recipe `recipe` failed on line 3 with exit code 100\u{1b}[0m\n",
 
 #[test]
 fn dump() {
-  let text ="
+  let text = r#"
 # this recipe does something
-recipe:
+recipe a b +d:
- @exit 100";
+ @exit 100"#;
   integration_test(
     &["--dump"],
     text,
     0,
     "# this recipe does something
-recipe:
+recipe a b +d:
     @exit 100
 ",
     "",
@@ -1481,3 +1481,59 @@ a b=":
 "#,
   );
 }
+
+#[test]
+fn variadic_recipe() {
+  integration_test(
+    &["a", "0", "1", "2", "3", " 4 "],
+    "
+a x y +z:
+  echo {{x}} {{y}} {{z}}
+",
+    0,
+    "0 1 2 3 4\n",
+    "echo 0 1 2 3  4 \n",
+  );
+}
+
+#[test]
+fn variadic_ignore_default() {
+  integration_test(
+    &["a", "0", "1", "2", "3", " 4 "],
+    "
+a x y +z='HELLO':
+  echo {{x}} {{y}} {{z}}
+",
+    0,
+    "0 1 2 3 4\n",
+    "echo 0 1 2 3  4 \n",
+  );
+}
+
+#[test]
+fn variadic_use_default() {
+  integration_test(
+    &["a", "0", "1"],
+    "
+a x y +z='HELLO':
+  echo {{x}} {{y}} {{z}}
+",
+    0,
+    "0 1 HELLO\n",
+    "echo 0 1 HELLO\n",
+  );
+}
+
+#[test]
+fn variadic_too_few() {
+  integration_test(
+    &["a", "0", "1"],
+    "
+a x y +z:
+  echo {{x}} {{y}} {{z}}
+",
+    255,
+    "",
+    "error: Recipe `a` got 2 arguments but takes at least 3\n",
+  );
+}

src/lib.rs

@@ -19,6 +19,7 @@ pub use app::app;
 
 use app::UseColor;
 use regex::Regex;
+use std::borrow::Cow;
 use std::collections::{BTreeMap as Map, BTreeSet as Set};
 use std::fmt::Display;
 use std::io::prelude::*;
@@ -68,28 +69,33 @@ fn contains<T: PartialOrd>(range: &Range<T>,  i: T) -> bool {
 
 #[derive(PartialEq, Debug)]
 struct Recipe<'a> {
-  line_number:       usize,
-  name:              &'a str,
-  doc:               Option<&'a str>,
-  lines:             Vec<Vec<Fragment<'a>>>,
   dependencies:      Vec<&'a str>,
   dependency_tokens: Vec<Token<'a>>,
+  doc:               Option<&'a str>,
+  line_number:       usize,
+  lines:             Vec<Vec<Fragment<'a>>>,
+  name:              &'a str,
   parameters:        Vec<Parameter<'a>>,
-  shebang:           bool,
   quiet:             bool,
+  shebang:           bool,
 }
 
 #[derive(PartialEq, Debug)]
 struct Parameter<'a> {
-  name:    &'a str,
   default:  Option<String>,
+  name:     &'a str,
   token:    Token<'a>,
+  variadic: bool,
 }
 
 impl<'a> Display for Parameter<'a> {
   fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
     let green = maybe_green(f.alternate());
     let cyan = maybe_cyan(f.alternate());
+    let purple = maybe_purple(f.alternate());
+    if self.variadic {
+      write!(f, "{}", purple.paint("+"))?;
+    }
     write!(f, "{}", cyan.paint(self.name))?;
     if let Some(ref default) = self.default {
       let escaped = default.chars().flat_map(char::escape_default).collect::<String>();;
@@ -275,8 +281,12 @@ impl<'a> Recipe<'a> {
   fn argument_range(&self) -> Range<usize> {
     self.parameters.iter().filter(|p| !p.default.is_some()).count()
       ..
+    if self.parameters.iter().any(|p| p.variadic) {
+      std::usize::MAX
+    } else {
       self.parameters.len() + 1
     }
+  }
 
   fn run(
     &self,
@@ -290,16 +300,30 @@ impl<'a> Recipe<'a> {
       warn!("{}===> Running recipe `{}`...{}", cyan.prefix(), self.name, cyan.suffix());
     }
 
-    let argument_map = self.parameters.iter().enumerate()
+    let mut argument_map = Map::new();
-      .map(|(i, parameter)| if i < arguments.len() {
+
-        Ok((parameter.name, arguments[i]))
+    let mut rest = arguments;
-      } else if let Some(ref default) = parameter.default {
+    for parameter in &self.parameters {
-        Ok((parameter.name, default.as_str()))
+      let value = if rest.is_empty() {
-      } else {
+        match parameter.default {
-        Err(RunError::InternalError{
+          Some(ref default) => Cow::Borrowed(default.as_str()),
+          None => return Err(RunError::InternalError{
             message: "missing parameter without default".to_string()
-        })
+          }),
-      }).collect::<Result<Vec<_>, _>>()?.into_iter().collect();
+        }
+      } else {
+        if parameter.variadic {
+          let value = Cow::Owned(rest.to_vec().join(" "));
+          rest = &[];
+          value
+        } else {
+          let value = Cow::Borrowed(rest[0]);
+          rest = &rest[1..];
+          value
+        }
+      };
+      argument_map.insert(parameter.name, value);
+    }
 
     let mut evaluator = Evaluator {
       evaluated:   empty(),
@@ -689,7 +713,7 @@ impl<'a, 'b> Evaluator<'a, 'b> {
   fn evaluate_line(
     &mut self,
     line:      &[Fragment<'a>],
-    arguments: &Map<&str, &str>
+    arguments: &Map<&str, Cow<str>>
   ) -> Result<String, RunError<'a>> {
     let mut evaluated = String::new();
     for fragment in line {
@@ -727,7 +751,7 @@ impl<'a, 'b> Evaluator<'a, 'b> {
   fn evaluate_expression(
     &mut self,
     expression: &Expression<'a>,
-    arguments: &Map<&str, &str>
+    arguments: &Map<&str, Cow<str>>
   ) -> Result<String, RunError<'a>> {
     Ok(match *expression {
       Expression::Variable{name, ..} => {
@@ -786,6 +810,7 @@ enum ErrorKind<'a> {
   OuterShebang,
   ParameterShadowsVariable{parameter: &'a str},
   RequiredParameterFollowsDefaultParameter{parameter: &'a str},
+  ParameterFollowsVariadicParameter{parameter: &'a str},
   UndefinedVariable{variable: &'a str},
   UnexpectedToken{expected: Vec<TokenKind>, found: TokenKind},
   UnknownDependency{recipe: &'a str, unknown: &'a str},
@@ -1002,6 +1027,14 @@ fn maybe_cyan(colors: bool) -> ansi_term::Style {
   }
 }
 
+fn maybe_purple(colors: bool) -> ansi_term::Style {
+  if colors {
+    ansi_term::Style::new().fg(ansi_term::Color::Purple)
+  } else {
+    ansi_term::Style::default()
+  }
+}
+
 fn maybe_bold(colors: bool) -> ansi_term::Style {
   if colors {
     ansi_term::Style::new().bold()
@@ -1066,6 +1099,9 @@ impl<'a> Display for CompileError<'a> {
       RequiredParameterFollowsDefaultParameter{parameter} => {
         writeln!(f, "non-default parameter `{}` follows default parameter", parameter)?;
       }
+      ParameterFollowsVariadicParameter{parameter} => {
+        writeln!(f, "parameter `{}` follows a varidic parameter", parameter)?;
+      }
       MixedLeadingWhitespace{whitespace} => {
         writeln!(f,
           "found a mix of tabs and spaces in leading whitespace: `{}`\n\
@@ -1846,8 +1882,28 @@ impl<'a> Parser<'a> {
     }
 
     let mut parsed_parameter_with_default = false;
+    let mut parsed_variadic_parameter = false;
     let mut parameters: Vec<Parameter> = vec![];
-    while let Some(parameter) = self.accept(Name) {
+    loop {
+      let plus = self.accept(Plus);
+
+      let parameter = match self.accept(Name) {
+        Some(parameter) => parameter,
+        None            => if let Some(plus) = plus {
+          return Err(self.unexpected_token(&plus, &[Name]));
+        } else {
+          break
+        },
+      };
+
+      let variadic = plus.is_some();
+
+      if parsed_variadic_parameter {
+        return Err(parameter.error(ErrorKind::ParameterFollowsVariadicParameter {
+          parameter: parameter.lexeme,
+        }));
+      }
+
       if parameters.iter().any(|p| p.name == parameter.lexeme) {
         return Err(parameter.error(ErrorKind::DuplicateParameter {
           recipe: name.lexeme, parameter: parameter.lexeme
@@ -1873,11 +1929,13 @@ impl<'a> Parser<'a> {
       }
 
       parsed_parameter_with_default |= default.is_some();
+      parsed_variadic_parameter = variadic;
 
       parameters.push(Parameter {
-        name:    parameter.lexeme,
         default:  default,
+        name:     parameter.lexeme,
         token:    parameter,
+        variadic: variadic,
       });
     }
 
@@ -1885,9 +1943,9 @@ impl<'a> Parser<'a> {
       // if we haven't accepted any parameters, an equals
       // would have been fine as part of an assignment
       if parameters.is_empty() {
-        return Err(self.unexpected_token(&token, &[Name, Colon, Equals]));
+        return Err(self.unexpected_token(&token, &[Name, Plus, Colon, Equals]));
       } else {
-        return Err(self.unexpected_token(&token, &[Name, Colon]));
+        return Err(self.unexpected_token(&token, &[Name, Plus, Colon]));
       }
     }
 

src/unit.rs

@@ -277,6 +277,26 @@ foo a="b\t":
   "#, r#"foo a='b\t':"#);
 }
 
+#[test]
+fn parse_variadic() {
+  parse_summary(r#"
+
+foo +a:
+
+
+  "#, r#"foo +a:"#);
+}
+
+#[test]
+fn parse_variadic_string_default() {
+  parse_summary(r#"
+
+foo +a="Hello":
+
+
+  "#, r#"foo +a='Hello':"#);
+}
+
 #[test]
 fn parse_raw_string_default() {
   parse_summary(r#"
@@ -400,7 +420,7 @@ fn missing_colon() {
     line:   0,
     column: 5,
     width:  Some(1),
-    kind:   ErrorKind::UnexpectedToken{expected: vec![Name, Colon], found: Eol},
+    kind:   ErrorKind::UnexpectedToken{expected: vec![Name, Plus, Colon], found: Eol},
   });
 }
 
@@ -456,6 +476,19 @@ fn missing_default_backtick() {
   });
 }
 
+#[test]
+fn parameter_after_variadic() {
+  let text = "foo +a bbb:";
+  parse_error(text, CompileError {
+    text:   text,
+    index:  7,
+    line:   0,
+    column: 7,
+    width:  Some(3),
+    kind:   ErrorKind::ParameterFollowsVariadicParameter{parameter: "bbb"}
+  });
+}
+
 #[test]
 fn required_after_default() {
   let text = "hello arg='foo' bar:";
@@ -825,6 +858,19 @@ fn unknown_second_interpolation_variable() {
   });
 }
 
+#[test]
+fn plus_following_parameter() {
+  let text = "a b c+:";
+  parse_error(text, CompileError {
+    text:   text,
+    index:  5,
+    line:   0,
+    column: 5,
+    width:  Some(1),
+    kind:   ErrorKind::UnexpectedToken{expected: vec![Name], found: Plus},
+  });
+}
+
 #[test]
 fn tokenize_order() {
   let text = r"
@@ -913,6 +959,19 @@ fn missing_some_arguments() {
   }
 }
 
+#[test]
+fn missing_some_arguments_variadic() {
+  match parse_success("a b c +d:").run(&["a", "B", "C"], &Default::default()).unwrap_err() {
+    RunError::ArgumentCountMismatch{recipe, found, min, max} => {
+      assert_eq!(recipe, "a");
+      assert_eq!(found, 2);
+      assert_eq!(min, 3);
+      assert_eq!(max, super::std::usize::MAX - 1);
+    },
+    other => panic!("expected an code run error, but got: {}", other),
+  }
+}
+
 #[test]
 fn missing_all_arguments() {
   match parse_success("a b c d:\n echo {{b}}{{c}}{{d}}")