Allow ignore line endings inside delimiters (#717)

Modify the lexer to keep track of opening `({[` and closing `]})` delimiters.
When the lexer would emit an eol or indent outside of a recipe when there
is at least one open delimiter, emit a whitespace token instead.

This allows expressions to be split on multiple lines, like so:

    x := if 'a' == 'b' {
      'x'
    } else {
      'y'
    }

This does not work inside of recipe body interpolations, although this
restriction might relaxed in the future.

src/common.rs

@@ -45,16 +45,16 @@ pub(crate) use crate::{
   assignment_resolver::AssignmentResolver, binding::Binding, color::Color,
   compilation_error::CompilationError, compilation_error_kind::CompilationErrorKind,
   compiler::Compiler, config::Config, config_error::ConfigError, count::Count,
-  dependency::Dependency, enclosure::Enclosure, evaluator::Evaluator, expression::Expression,
-  fragment::Fragment, function::Function, function_context::FunctionContext,
-  interrupt_guard::InterruptGuard, interrupt_handler::InterruptHandler, item::Item,
-  justfile::Justfile, keyword::Keyword, lexer::Lexer, line::Line, list::List,
-  load_error::LoadError, module::Module, name::Name, output_error::OutputError,
-  parameter::Parameter, parameter_kind::ParameterKind, parser::Parser, platform::Platform,
-  position::Position, positional::Positional, recipe::Recipe, recipe_context::RecipeContext,
-  recipe_resolver::RecipeResolver, runtime_error::RuntimeError, scope::Scope, search::Search,
-  search_config::SearchConfig, search_error::SearchError, set::Set, setting::Setting,
-  settings::Settings, shebang::Shebang, show_whitespace::ShowWhitespace,
+  delimiter::Delimiter, dependency::Dependency, enclosure::Enclosure, evaluator::Evaluator,
+  expression::Expression, fragment::Fragment, function::Function,
+  function_context::FunctionContext, interrupt_guard::InterruptGuard,
+  interrupt_handler::InterruptHandler, item::Item, justfile::Justfile, keyword::Keyword,
+  lexer::Lexer, line::Line, list::List, load_error::LoadError, module::Module, name::Name,
+  output_error::OutputError, parameter::Parameter, parameter_kind::ParameterKind, parser::Parser,
+  platform::Platform, position::Position, positional::Positional, recipe::Recipe,
+  recipe_context::RecipeContext, recipe_resolver::RecipeResolver, runtime_error::RuntimeError,
+  scope::Scope, search::Search, search_config::SearchConfig, search_error::SearchError, set::Set,
+  setting::Setting, settings::Settings, shebang::Shebang, show_whitespace::ShowWhitespace,
   string_literal::StringLiteral, subcommand::Subcommand, suggestion::Suggestion, table::Table,
   thunk::Thunk, token::Token, token_kind::TokenKind, unresolved_dependency::UnresolvedDependency,
   unresolved_recipe::UnresolvedRecipe, use_color::UseColor, variables::Variables,

src/compilation_error.rs

@@ -209,6 +209,22 @@ impl Display for CompilationError<'_> {
       UnknownStartOfToken => {
         writeln!(f, "Unknown start of token:")?;
       },
+      MismatchedClosingDelimiter {
+        open,
+        open_line,
+        close,
+      } => {
+        writeln!(
+          f,
+          "Mismatched closing delimiter `{}`. (Did you mean to close the `{}` on line {}?)",
+          close.close(),
+          open.open(),
+          open_line.ordinal(),
+        )?;
+      },
+      UnexpectedClosingDelimiter { close } => {
+        writeln!(f, "Unexpected closing delimiter `{}`", close.close())?;
+      },
       UnpairedCarriageReturn => {
         writeln!(f, "Unpaired carriage return")?;
       },

src/compilation_error_kind.rs

@@ -97,6 +97,14 @@ pub(crate) enum CompilationErrorKind<'src> {
     setting: &'src str,
   },
   UnpairedCarriageReturn,
+  UnexpectedClosingDelimiter {
+    close: Delimiter,
+  },
+  MismatchedClosingDelimiter {
+    close:     Delimiter,
+    open:      Delimiter,
+    open_line: usize,
+  },
   UnterminatedInterpolation,
   UnterminatedString,
   UnterminatedBacktick,

src/delimiter.rs

@@ -0,0 +1,24 @@
+#[derive(PartialEq, Eq, Debug, Copy, Clone)]
+pub(crate) enum Delimiter {
+  Brace,
+  Bracket,
+  Paren,
+}
+
+impl Delimiter {
+  pub(crate) fn open(self) -> char {
+    match self {
+      Self::Brace => '{',
+      Self::Bracket => '[',
+      Self::Paren => '(',
+    }
+  }
+
+  pub(crate) fn close(self) -> char {
+    match self {
+      Self::Brace => '}',
+      Self::Bracket => ']',
+      Self::Paren => ')',
+    }
+  }
+}

src/lexer.rs

@@ -32,6 +32,8 @@ pub(crate) struct Lexer<'src> {
   indentation:         Vec<&'src str>,
   /// Current interpolation start token
   interpolation_start: Option<Token<'src>>,
+  /// Current open delimiters
+  open_delimiters:     Vec<(Delimiter, usize)>,
 }
 
 impl<'src> Lexer<'src> {
@@ -59,6 +61,7 @@ impl<'src> Lexer<'src> {
       recipe_body_pending: false,
       recipe_body: false,
       interpolation_start: None,
+      open_delimiters: Vec::new(),
       chars,
       next,
       src,
@@ -431,14 +434,15 @@ impl<'src> Lexer<'src> {
           self.advance()?;
         }
 
-        let indentation = self.lexeme();
-
-        self.indentation.push(indentation);
-
-        self.token(Indent);
-
-        if self.recipe_body_pending {
-          self.recipe_body = true;
+        if self.open_delimiters() {
+          self.token(Whitespace);
+        } else {
+          let indentation = self.lexeme();
+          self.indentation.push(indentation);
+          self.token(Indent);
+          if self.recipe_body_pending {
+            self.recipe_body = true;
+          }
         }
 
         Ok(())
@@ -452,23 +456,24 @@ impl<'src> Lexer<'src> {
       '!' => self.lex_bang(),
       '*' => self.lex_single(Asterisk),
       '@' => self.lex_single(At),
-      '[' => self.lex_single(BracketL),
-      ']' => self.lex_single(BracketR),
+      '[' => self.lex_delimiter(BracketL),
+      ']' => self.lex_delimiter(BracketR),
       '=' => self.lex_choice('=', EqualsEquals, Equals),
       ',' => self.lex_single(Comma),
       ':' => self.lex_colon(),
-      '(' => self.lex_single(ParenL),
-      ')' => self.lex_single(ParenR),
-      '{' => self.lex_single(BraceL),
-      '}' => self.lex_single(BraceR),
+      '(' => self.lex_delimiter(ParenL),
+      ')' => self.lex_delimiter(ParenR),
+      '{' => self.lex_delimiter(BraceL),
+      '}' => self.lex_delimiter(BraceR),
       '+' => self.lex_single(Plus),
-      '\n' => self.lex_single(Eol),
-      '\r' => self.lex_cr_lf(),
       '#' => self.lex_comment(),
       '`' => self.lex_backtick(),
-      ' ' | '\t' => self.lex_whitespace(),
-      '\'' => self.lex_raw_string(),
+      ' ' => self.lex_whitespace(),
       '"' => self.lex_cooked_string(),
+      '\'' => self.lex_raw_string(),
+      '\n' => self.lex_eol(),
+      '\r' => self.lex_eol(),
+      '\t' => self.lex_whitespace(),
       _ if Self::is_identifier_start(start) => self.lex_identifier(),
       _ => {
         self.advance()?;
@@ -589,6 +594,53 @@ impl<'src> Lexer<'src> {
     Ok(())
   }
 
+  /// Lex an opening or closing delimiter
+  fn lex_delimiter(&mut self, kind: TokenKind) -> CompilationResult<'src, ()> {
+    use Delimiter::*;
+
+    match kind {
+      BraceL => self.open_delimiter(Brace),
+      BraceR => self.close_delimiter(Brace)?,
+      BracketL => self.open_delimiter(Bracket),
+      BracketR => self.close_delimiter(Bracket)?,
+      ParenL => self.open_delimiter(Paren),
+      ParenR => self.close_delimiter(Paren)?,
+      _ =>
+        return Err(self.internal_error(format!(
+          "Lexer::lex_delimiter called with non-delimiter token: `{}`",
+          kind,
+        ))),
+    }
+
+    // Emit the delimiter token
+    self.lex_single(kind)
+  }
+
+  /// Push a delimiter onto the open delimiter stack
+  fn open_delimiter(&mut self, delimiter: Delimiter) {
+    self
+      .open_delimiters
+      .push((delimiter, self.token_start.line));
+  }
+
+  /// Pop a delimiter from the open delimiter stack and error if incorrect type
+  fn close_delimiter(&mut self, close: Delimiter) -> CompilationResult<'src, ()> {
+    match self.open_delimiters.pop() {
+      Some((open, _)) if open == close => Ok(()),
+      Some((open, open_line)) => Err(self.error(MismatchedClosingDelimiter {
+        open,
+        close,
+        open_line,
+      })),
+      None => Err(self.error(UnexpectedClosingDelimiter { close })),
+    }
+  }
+
+  /// Return true if there are any unclosed delimiters
+  fn open_delimiters(&self) -> bool {
+    !self.open_delimiters.is_empty()
+  }
+
   /// Lex a token starting with '!'
   fn lex_bang(&mut self) -> CompilationResult<'src, ()> {
     self.presume('!')?;
@@ -621,14 +673,22 @@ impl<'src> Lexer<'src> {
   }
 
   /// Lex a carriage return and line feed
-  fn lex_cr_lf(&mut self) -> CompilationResult<'src, ()> {
-    self.presume('\r')?;
-
-    if !self.accepted('\n')? {
-      return Err(self.error(UnpairedCarriageReturn));
+  fn lex_eol(&mut self) -> CompilationResult<'src, ()> {
+    if self.accepted('\r')? {
+      if !self.accepted('\n')? {
+        return Err(self.error(UnpairedCarriageReturn));
+      }
+    } else {
+      self.presume('\n')?;
     }
 
-    self.token(Eol);
+    // Emit an eol if there are no open delimiters, otherwise emit a whitespace
+    // token.
+    if self.open_delimiters() {
+      self.token(Whitespace);
+    } else {
+      self.token(Eol);
+    }
 
     Ok(())
   }
@@ -958,8 +1018,8 @@ mod tests {
 
   test! {
     name:   brace_r,
-    text:   "}",
-    tokens: (BraceR),
+    text:   "{}",
+    tokens: (BraceL, BraceR),
   }
 
   test! {
@@ -970,8 +1030,8 @@ mod tests {
 
   test! {
     name:   brace_rrr,
-    text:   "}}}",
-    tokens: (BraceR, BraceR, BraceR),
+    text:   "{{{}}}",
+    tokens: (BraceL, BraceL, BraceL, BraceR, BraceR, BraceR),
   }
 
   test! {
@@ -1801,7 +1861,7 @@ mod tests {
 
   test! {
     name: tokenize_parens,
-    text: "((())) )abc(+",
+    text: "((())) ()abc(+",
     tokens: (
       ParenL,
       ParenL,
@@ -1810,6 +1870,7 @@ mod tests {
       ParenR,
       ParenR,
       Whitespace,
+      ParenL,
       ParenR,
       Identifier:"abc",
       ParenL,
@@ -1846,8 +1907,18 @@ mod tests {
 
   test! {
     name:   brackets,
-    text:   "][",
-    tokens: (BracketR, BracketL),
+    text:   "[][]",
+    tokens: (BracketL, BracketR, BracketL, BracketR),
+  }
+
+  test! {
+    name:   open_delimiter_eol,
+    text:   "[\n](\n){\n}",
+    tokens: (
+      BracketL, Whitespace:"\n", BracketR,
+      ParenL, Whitespace:"\n", ParenR,
+      BraceL, Whitespace:"\n", BraceR
+    ),
   }
 
   error! {
@@ -2049,6 +2120,20 @@ mod tests {
     kind:   UnexpectedCharacter { expected: '=' },
   }
 
+  error! {
+    name:   mismatched_closing_brace,
+    input:  "(]",
+    offset: 1,
+    line:   0,
+    column: 1,
+    width:  0,
+    kind:   MismatchedClosingDelimiter {
+      open:      Delimiter::Paren,
+      close:     Delimiter::Bracket,
+      open_line: 0,
+    },
+  }
+
   #[test]
   fn presume_error() {
     assert_matches!(

src/lib.rs

@@ -65,6 +65,7 @@ mod config;
 mod config_error;
 mod count;
 mod default;
+mod delimiter;
 mod dependency;
 mod empty;
 mod enclosure;

src/summary.rs

@@ -244,8 +244,8 @@ impl Expression {
       } => Expression::Conditional {
         lhs:       Box::new(Expression::new(lhs)),
         rhs:       Box::new(Expression::new(rhs)),
-        then:      Box::new(Expression::new(lhs)),
-        otherwise: Box::new(Expression::new(rhs)),
+        then:      Box::new(Expression::new(then)),
+        otherwise: Box::new(Expression::new(otherwise)),
         inverted:  *inverted,
       },
       StringLiteral { string_literal } => Expression::String {

tests/delimiters.rs

@@ -0,0 +1,104 @@
+use crate::common::*;
+
+test! {
+  name: mismatched_delimiter,
+  justfile: "(]",
+  stderr: "
+    error: Mismatched closing delimiter `]`. (Did you mean to close the `(` on line 1?)
+      |
+    1 | (]
+      |  ^
+  ",
+  status: EXIT_FAILURE,
+}
+
+test! {
+  name: unexpected_delimiter,
+  justfile: "]",
+  stderr: "
+    error: Unexpected closing delimiter `]`
+      |
+    1 | ]
+      | ^
+  ",
+  status: EXIT_FAILURE,
+}
+
+test! {
+  name: paren_continuation,
+  justfile: "
+    x := (
+          'a'
+              +
+      'b'
+    )
+
+    foo:
+      echo {{x}}
+  ",
+  stdout: "ab\n",
+  stderr: "echo ab\n",
+}
+
+test! {
+  name: brace_continuation,
+  justfile: "
+    x := if '' == '' {
+      'a'
+    } else {
+      'b'
+    }
+
+    foo:
+      echo {{x}}
+  ",
+  stdout: "a\n",
+  stderr: "echo a\n",
+}
+
+test! {
+  name: bracket_continuation,
+  justfile: "
+    set shell := [
+      'sh',
+      '-cu',
+    ]
+
+    foo:
+      echo foo
+  ",
+  stdout: "foo\n",
+  stderr: "echo foo\n",
+}
+
+test! {
+  name: dependency_continuation,
+  justfile: "
+    foo: (
+    bar 'bar'
+    )
+      echo foo
+
+    bar x:
+      echo {{x}}
+  ",
+  stdout: "bar\nfoo\n",
+  stderr: "echo bar\necho foo\n",
+}
+
+test! {
+  name: no_interpolation_continuation,
+  justfile: "
+    foo:
+      echo {{ (
+        'a' + 'b')}}
+  ",
+  stdout: "",
+  stderr: "
+    error: Unterminated interpolation
+      |
+    2 |   echo {{ (
+      |        ^^
+  ",
+  status: EXIT_FAILURE,
+}

tests/lib.rs

@@ -6,6 +6,7 @@ mod common;
 mod choose;
 mod completions;
 mod conditional;
+mod delimiters;
 mod dotenv;
 mod edit;
 mod error_messages;