fix: match completion prefix against unescaped names (#460)

When using `complete ... descriptions=#true`, prefix matching was done
against escaped strings (e.g., `test\:integration`) instead of unescaped
names (`test:integration`). This caused completions to fail when user
input contained an unescaped colon.

Fix by moving the filter to after the map that unescapes the names.

This bug caused a problem with mise: there was no shell completion if
you entered `mise test:i<tab>` even if there was a `test:integration`
task. `mise run test:i<tab>` was *not* affected, that is treated
differently by `mise`'s `usage` spec.

------

I feel that the test could be more readable, I might do that in a
subsequent PR. I think all `complete_word` tests could use the fish
syntax instead of the zsh syntax, so e.g.

```rust
"test:unit\tRun unit tests\ntest:integration\tRun integration tests\nbuild\tBuild the project\n"
// instead of 
"'test\\\\:unit'\\:'Run unit tests'\n'test\\\\:integration'\\:'Run integration tests'\n'build'\\:'Build the project'\n"
```

Let me know if you prefer I do that refactor first to make the diff here
more readable (but it's not *that* bad)

**Update:** Apparently, that'd also make Copilot happer. Here's a draft:
ilyagr@fish-refactor . Again, I'm happy
to reorder the commits so that the cleaner syntax comes first. The
biggest win from the refactor is in the test added in this PR, but
others are also easier to read IMO for somebody unfamiliar with either
shell's syntax.

------

This was mostly debugged by AI. If the fix is not correct, it could be
considered a bug report (but it seems good to me).

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Fixes completion prefix matching when `complete ...
descriptions=#true` by filtering after unescaping `name:description`
outputs.
> 
> - In `complete_word.rs`, process command output lines first (unescape
and split) then filter by `ctoken`, so prefixes match unescaped names
containing colons
> - Adds test `complete_word_escaped_colons_in_completions` and example
`colon-in-completions.usage.kdl` to validate colon-containing
completions
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
e24490f. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Ilya Grigoriev <[email protected]>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

Author: ilyagr

cli/src/cli/complete_word.rs

@@ -281,7 +281,6 @@ impl CompleteWord {
             let re = regex!(r"[^\\]:");
             return Ok(stdout
                 .lines()
-                .filter(|l| l.starts_with(ctoken))
                 .map(|l| {
                     if complete.descriptions {
                         match re.find(l).map(|m| l.split_at(m.end() - 1)) {
@@ -298,6 +297,7 @@ impl CompleteWord {
                         (l.trim().to_string(), String::new())
                     }
                 })
+                .filter(|(name, _)| name.starts_with(ctoken))
                 .collect());
         }
 

cli/tests/complete_word.rs

@@ -252,6 +252,30 @@ fn complete_word_subcommands_without_shell() {
     cmd.assert().success().stdout(contains("install"));
 }
 
+#[test]
+fn complete_word_escaped_colons_in_completions() {
+    // When completions contain colons, they are escaped as \: in the name:description format.
+    // Prefix matching should work against the unescaped names.
+
+    // Typing "test:" should match "test:unit" and "test:integration" (unescaped)
+    assert_cmd("colon-in-completions.usage.kdl", &["--", "run", "test:"]).stdout(
+        "'test\\\\:unit'\\:'Run unit tests'\n'test\\\\:integration'\\:'Run integration tests'\n",
+    );
+
+    // Typing "test" should also match (prefix of the unescaped name)
+    assert_cmd("colon-in-completions.usage.kdl", &["--", "run", "test"]).stdout(
+        "'test\\\\:unit'\\:'Run unit tests'\n'test\\\\:integration'\\:'Run integration tests'\n",
+    );
+
+    // Typing "build" should only match "build"
+    assert_cmd("colon-in-completions.usage.kdl", &["--", "run", "build"])
+        .stdout("'build'\\:'Build the project'\n");
+
+    // Empty input should match all completions
+    assert_cmd("colon-in-completions.usage.kdl", &["--", "run", ""])
+        .stdout("'test\\\\:unit'\\:'Run unit tests'\n'test\\\\:integration'\\:'Run integration tests'\n'build'\\:'Build the project'\n");
+}
+
 fn cmd(example: &str, shell: Option<&str>) -> Command {
     let mut cmd = Command::new(cargo::cargo_bin!("usage"));
     cmd.args(["cw"]);

examples/colon-in-completions.usage.kdl

@@ -0,0 +1,9 @@
+// Test case for completions containing colons in their names
+// The completer outputs escaped colons (\:) per the usage spec
+
+cmd "run" {
+    arg "task"
+}
+
+// Completer outputs escaped colons in name:description format
+complete "task" descriptions=#true run="echo \"test\\:unit:Run unit tests\ntest\\:integration:Run integration tests\nbuild:Build the project\""