Update zsh completion file (#606)

- Complete variable names after `--set`
- Complete recipe names
- Display recipe signature and body below command line
- Modify completions subcommand to produce enhanced zsh completion script

completions/just.zsh

@@ -14,18 +14,18 @@ _just() {
     fi
 
     local context curcontext="$curcontext" state line
-    _arguments "${_arguments_options[@]}" \
+    local common=(
 '--color=[Print colorful output]: :(auto always never)' \
 '-f+[Use <JUSTFILE> as justfile.]' \
 '--justfile=[Use <JUSTFILE> as justfile.]' \
-'*--set=[Override <VARIABLE> with <VALUE>]' \
+'*--set[Override <VARIABLE> with <VALUE>]: :_just_variables' \
 '--shell=[Invoke <SHELL> to run recipes]' \
 '*--shell-arg=[Invoke shell with <SHELL-ARG> as an argument]' \
 '-d+[Use <WORKING-DIRECTORY> as working directory. --justfile must also be set]' \
 '--working-directory=[Use <WORKING-DIRECTORY> as working directory. --justfile must also be set]' \
 '--completions=[Print shell completion script for <SHELL>]: :(zsh bash fish powershell elvish)' \
-'-s+[Show information about <RECIPE>]' \
-'--show=[Show information about <RECIPE>]' \
+'-s+[Show information about <RECIPE>]: :_just_commands' \
+'--show=[Show information about <RECIPE>]: :_just_commands' \
 '(-q --quiet)--dry-run[Print what just would do without doing it]' \
 '--highlight[Highlight echoed recipe lines in bold]' \
 '--no-highlight[Don'\''t highlight echoed recipe lines in bold]' \
@@ -47,17 +47,50 @@ _just() {
 '--help[Print help information]' \
 '-V[Print version information]' \
 '--version[Print version information]' \
-'::ARGUMENTS -- Overrides and recipe(s) to run, defaulting to the first recipe in the justfile:_files' \
-&& ret=0
+)
 
+    _arguments "${_arguments_options[@]}" $common \
+        '1: :_just_commands' \
+        '*: :->args' \
+        && ret=0
+
+    case $state in
+        args)
+            curcontext="${curcontext%:*}-${words[2]}:"
+
+            local lastarg=${words[${#words}]}
+
+            if [[ ${lastarg} = */* ]]; then
+                # Arguments contain slash would be recognised as a file
+                _arguments -s -S $common '*:: :_files'
+            else
+                # Show usage message
+                _message "`just --show ${words[2]}`"
+                # Or complete with other commands
+                #_arguments -s -S $common '*:: :_just_commands'
+            fi
+        ;;
+    esac
+
+    return ret
 }
 
 (( $+functions[_just_commands] )) ||
 _just_commands() {
     local commands; commands=(
-        
+        ${${${(M)"${(f)$(_call_program commands just --list)}":#    *}/ ##/}/ ##/:Args: }
     )
+
     _describe -t commands 'just commands' commands "$@"
 }
 
+(( $+functions[_just_variables] )) ||
+_just_variables() {
+    local variables; variables=(
+        ${(s: :)$(_call_program commands just --variables)}
+    )
+
+    _describe -t variables 'variables' variables
+}
+
 _just "$@"

src/config.rs

@@ -417,7 +417,7 @@ impl Config {
     }
 
     if let Completions { shell } = self.subcommand {
-      return Self::completions(&shell);
+      return Subcommand::completions(&shell);
     }
 
     let search =
@@ -459,21 +459,6 @@ impl Config {
     }
   }
 
-  fn completions(shell: &str) -> Result<(), i32> {
-    let shell = shell
-      .parse::<clap::Shell>()
-      .expect("Invalid value for clap::Shell");
-
-    let buffer = Vec::new();
-    let mut cursor = Cursor::new(buffer);
-    Self::app().gen_completions_to(env!("CARGO_PKG_NAME"), shell, &mut cursor);
-    let buffer = cursor.into_inner();
-    let text = String::from_utf8(buffer).expect("Clap completion not UTF-8");
-    println!("{}", text.trim());
-
-    Ok(())
-  }
-
   fn dump(justfile: Justfile) -> Result<(), i32> {
     println!("{}", justfile);
     Ok(())

src/subcommand.rs

@@ -22,3 +22,113 @@ pub(crate) enum Subcommand {
   Summary,
   Variables,
 }
+
+const ZSH_COMPLETION_REPLACEMENTS: &[(&str, &str)] = &[
+  (
+    r#"    _arguments "${_arguments_options[@]}" \"#,
+    r#"    local common=("#,
+  ),
+  (
+    r#"'*--set=[Override <VARIABLE> with <VALUE>]' \"#,
+    r#"'*--set[Override <VARIABLE> with <VALUE>]: :_just_variables' \"#,
+  ),
+  (
+    r#"'-s+[Show information about <RECIPE>]' \
+'--show=[Show information about <RECIPE>]' \"#,
+    r#"'-s+[Show information about <RECIPE>]: :_just_commands' \
+'--show=[Show information about <RECIPE>]: :_just_commands' \"#,
+  ),
+  (
+    "'::ARGUMENTS -- Overrides and recipe(s) to run, defaulting to the first recipe in the \
+     justfile:_files' \\
+&& ret=0
+\x20\x20\x20\x20
+",
+    r#")
+
+    _arguments "${_arguments_options[@]}" $common \
+        '1: :_just_commands' \
+        '*: :->args' \
+        && ret=0
+
+    case $state in
+        args)
+            curcontext="${curcontext%:*}-${words[2]}:"
+
+            local lastarg=${words[${#words}]}
+
+            if [[ ${lastarg} = */* ]]; then
+                # Arguments contain slash would be recognised as a file
+                _arguments -s -S $common '*:: :_files'
+            else
+                # Show usage message
+                _message "`just --show ${words[2]}`"
+                # Or complete with other commands
+                #_arguments -s -S $common '*:: :_just_commands'
+            fi
+        ;;
+    esac
+
+    return ret
+"#,
+  ),
+  (
+    "    local commands; commands=(
+\x20\x20\x20\x20\x20\x20\x20\x20
+    )",
+    r#"    local commands; commands=(
+        ${${${(M)"${(f)$(_call_program commands just --list)}":#    *}/ ##/}/ ##/:Args: }
+    )
+"#,
+  ),
+  (
+    r#"_just "$@""#,
+    r#"(( $+functions[_just_variables] )) ||
+_just_variables() {
+    local variables; variables=(
+        ${(s: :)$(_call_program commands just --variables)}
+    )
+
+    _describe -t variables 'variables' variables
+}
+
+_just "$@""#,
+  ),
+];
+
+impl Subcommand {
+  pub(crate) fn completions(shell: &str) -> Result<(), i32> {
+    fn replace(haystack: &mut String, needle: &str, replacement: &str) -> Result<(), i32> {
+      if let Some(index) = haystack.find(needle) {
+        haystack.replace_range(index..index + needle.len(), replacement);
+        Ok(())
+      } else {
+        eprintln!("Failed to find text:");
+        eprintln!("{}", needle);
+        eprintln!("…in completion script:");
+        eprintln!("{}", haystack);
+        Err(EXIT_FAILURE)
+      }
+    }
+
+    let shell = shell
+      .parse::<clap::Shell>()
+      .expect("Invalid value for clap::Shell");
+
+    let buffer = Vec::new();
+    let mut cursor = Cursor::new(buffer);
+    Config::app().gen_completions_to(env!("CARGO_PKG_NAME"), shell, &mut cursor);
+    let buffer = cursor.into_inner();
+    let mut script = String::from_utf8(buffer).expect("Clap completion not UTF-8");
+
+    if let clap::Shell::Zsh = shell {
+      for (needle, replacement) in ZSH_COMPLETION_REPLACEMENTS {
+        replace(&mut script, needle, replacement)?;
+      }
+    }
+
+    println!("{}", script.trim());
+
+    Ok(())
+  }
+}