Reorder simple command words in display

yash-syntax/CHANGELOG.md

@@ -18,6 +18,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
  is not followed by any name characters. Previously, it returned
  `Err(SyntaxError::UnclosedParam{…})` if `{` was followed by a non-name
  character other than `}`.
+- `impl std::fmt::Display for SimpleCommand` now prints the command words
+ after the redirections if there are no assignments and the first word looks
+ like a keyword.
 
 ### Fixed
 

yash-syntax/src/syntax.rs

@@ -73,6 +73,7 @@
 //! here-document contents omitted. To pretty-format an AST in multiple lines
 //! with here-document contents included, you can use ... TODO TBD.
 
+use crate::parser::lex::Keyword;
 use crate::parser::lex::Operator;
 use crate::parser::lex::TryFromOperatorError;
 use crate::source::Location;
@@ -964,15 +965,35 @@ impl SimpleCommand {
  pub fn is_one_word(&self) -> bool {
  self.assigns.is_empty() && self.words.len() == 1 && self.redirs.is_empty()
  }
+
+ /// Tests whether the first word of the simple command is a keyword.
+ #[must_use]
+ fn first_word_is_keyword(&self) -> bool {
+ let Some(word) = self.words.first() else {
+ return false;
+ };
+ let Some(literal) = word.to_string_if_literal() else {
+ return false;
+ };
+ literal.parse::<Keyword>().is_ok()
+ }
 }
 
 impl fmt::Display for SimpleCommand {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  let i1 = self.assigns.iter().map(|x| x as &dyn fmt::Display);
  let i2 = self.words.iter().map(|x| x as &dyn fmt::Display);
  let i3 = self.redirs.iter().map(|x| x as &dyn fmt::Display);
- write!(f, "{}", i1.chain(i2).chain(i3).format(" "))
- // TODO Avoid printing a keyword as the first word
+
+ if !self.assigns.is_empty() || !self.first_word_is_keyword() {
+ write!(f, "{}", i1.chain(i2).chain(i3).format(" "))
+ } else {
+ // If the simple command starts with an assignment or redirection,
+ // the first word may be a keyword which is treated as a plain word.
+ // In this case, we need to avoid the word being interpreted as a
+ // keyword by printing the assignment or redirection first.
+ write!(f, "{}", i3.chain(i2).format(" "))
+ }
  }
 }
 
@@ -1925,6 +1946,16 @@ mod tests {
  assert_eq!(command.to_string(), "foo=bar <<END 1<<-here");
  }
 
+ #[test]
+ fn simple_command_display_with_keyword() {
+ let command = SimpleCommand {
+ assigns: vec![],
+ words: vec!["if".parse().unwrap()],
+ redirs: vec!["<foo".parse().unwrap()].into(),
+ };
+ assert_eq!(command.to_string(), "<foo if");
+ }
+
  #[test]
  fn elif_then_display() {
  let condition: List = "c 1& c 2".parse().unwrap();