fix(stylelint): resolve extends/plugins against tool install directory (#2757)

Fixes #2700.

## Summary

Users on stylelint ≥17 hit `ConfigurationError: Could not find
"stylelint-config-standard"` even though qlty had installed the package
into its tool cache via `package_filters`. This PR makes two small,
targeted fixes:

1. **`qlty-plugins/plugins/linters/stylelint/plugin.toml`** — pass
`--config-basedir "${linter}"` to the `lint` (both version matchers) and
`format` scripts. `${linter}` interpolates to the plugin's tool install
directory, which is where qlty already installs the user's filtered npm
deps.
2. **`qlty-check/src/parser/stylelint.rs`** — harden the JSON parser to
skip leading non-JSON lines (Node 21 emits `ExperimentalWarning` to
stderr before stylelint's JSON report; stylelint ≥16 routes its report
to stderr). Slice from the first `[` so the parser tolerates the warning
while still surfacing genuinely malformed input.

## Why both changes are necessary

Without (1), the user hits the reported `ConfigurationError`. Stylelint
17's `resolveSilent` uses `import-meta-resolve` exclusively, which
doesn't honor `NODE_PATH`; stylelint 16 fell back to `resolve-from`
which did, which is why stylelint 16 users don't see the bug. Setting
`configBasedir` to the tool dir makes it stylelint's first resolution
root.

Without (2), applying (1) alone exchanges the `ConfigurationError` for a
parser failure, because Node 21 prints `ExperimentalWarning: Importing
JSON modules ...` to stderr before stylelint's JSON. The reporter would
hit this second error immediately after (1) lands.

## Verification

Added a plugin test fixture at
`qlty-plugins/plugins/linters/stylelint/fixtures/extends.in/` pinning
stylelint 17.3.0 + stylelint-config-standard 39.0.0. End-to-end
behaviour confirmed:

- **With both fixes applied:** test passes; `block-no-empty` violation
reported as expected. Snapshot: `__snapshots__/extends_v17.3.0.shot`.
- **Plugin.toml fix reverted (parser fix kept):** test fails with the
exact `ConfigurationError` from #2700. Confirms the plugin.toml change
is load-bearing.
- **Both reverted:** test fails with the parser error, confirming fix
(2) is also load-bearing.

Existing `basic` fixture at 14.6.1 and 16.15.0 still passes — no
regression.

Also added a `parse_strips_node_warning_prefix` unit test in
`qlty-check/src/parser/stylelint.rs`.

## Test plan

- [x] `cargo check` — clean
- [x] `cargo test --workspace` — all pass
- [x] `cd qlty-plugins/plugins && npm test --
--testPathPattern='linters/stylelint'` — 3/3 pass
- [x] Revert-and-reproduce verified the fixture genuinely exercises the
bug path at stylelint 17.3.0
- [x] `qlty fmt` / `qlty check --level=low --fix` on touched files —
clean

## Notes / caveats

- The `${linter}` interpolation is quoted (`"${linter}"`) to survive
tool-cache paths with spaces, matching the `editorconfig-checker`
plugin's pattern.
- `--config-basedir` has been a stylelint CLI flag since 7.x (2017), so
both `<16.0.0` and `>=16.0.0` version matchers are safe.
- The parser's `extract_json_array` helper uses a simple `find('[')`
rather than line-by-line scanning. Stylelint's top-level output is
always a JSON array, and any leading `[` inside a warning message would
be rare and would still produce a parse error on the right-hand slice.
If this proves fragile we can tighten to line-scan.

Author: davehenton

qlty-check/src/parser/stylelint.rs

@@ -28,7 +28,8 @@ pub struct Stylelint {}
 impl Parser for Stylelint {
     fn parse(&self, _plugin_name: &str, output: &str) -> Result<Vec<Issue>> {
         let mut issues = vec![];
-        let files: Vec<StylelintFile> = serde_json::from_str(output)?;
+        let json = extract_json_array(output);
+        let files: Vec<StylelintFile> = serde_json::from_str(json)?;
 
         for file in files {
             for message in file.warnings {
@@ -62,6 +63,19 @@ impl Parser for Stylelint {
     }
 }
 
+// Node emits diagnostic warnings like `(node:XXX) ExperimentalWarning: ...`
+// to stderr before stylelint's own output, and stylelint >=16 routes its
+// JSON report to stderr. Skip leading non-JSON lines so the parser works
+// regardless of Node's diagnostic chatter. We scan for the first `[`, which
+// always begins stylelint's top-level array, and fall back to the full
+// output if none is found so malformed input still surfaces as a parse error.
+fn extract_json_array(output: &str) -> &str {
+    match output.find('[') {
+        Some(idx) => &output[idx..],
+        None => output,
+    }
+}
+
 fn severity_to_level(severity: String) -> Level {
     match severity.as_str() {
         // In eslint, issues come with a `fatal` attribute that we use to determine if the issue is Level::High or Level::Medium.
@@ -168,4 +182,25 @@ mod test {
               endColumn: 4
         "#);
     }
+
+    #[test]
+    fn parse_strips_node_warning_prefix() {
+        let input = "(node:543) ExperimentalWarning: Importing JSON modules is an experimental feature\n(Use `node --trace-warnings ...` to show where the warning was created)\n[{\"source\":\"/src/main.css\",\"warnings\":[{\"line\":1,\"column\":3,\"endLine\":1,\"endColumn\":5,\"rule\":\"block-no-empty\",\"severity\":\"error\",\"text\":\"Unexpected empty block (block-no-empty)\"}]}]";
+
+        let issues = Stylelint::default().parse("stylelint", input);
+        insta::assert_yaml_snapshot!(issues.unwrap(), @r#"
+        - tool: stylelint
+          ruleKey: block-no-empty
+          message: Unexpected empty block (block-no-empty)
+          level: LEVEL_MEDIUM
+          category: CATEGORY_LINT
+          location:
+            path: /src/main.css
+            range:
+              startLine: 1
+              startColumn: 3
+              endLine: 1
+              endColumn: 5
+        "#);
+    }
 }

qlty-plugins/plugins/linters/stylelint/fixtures/__snapshots__/extends_v17.3.0.shot

@@ -0,0 +1,27 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`linter=stylelint fixture=extends version=17.3.0 1`] = `
+{
+  "issues": [
+    {
+      "category": "CATEGORY_LINT",
+      "level": "LEVEL_MEDIUM",
+      "location": {
+        "path": "basic.in.css",
+        "range": {
+          "endColumn": 5,
+          "endLine": 1,
+          "startColumn": 3,
+          "startLine": 1,
+        },
+      },
+      "message": "Empty block (block-no-empty)",
+      "mode": "MODE_BLOCK",
+      "ruleKey": "block-no-empty",
+      "snippet": "a {}",
+      "snippetWithContext": "a {}",
+      "tool": "stylelint",
+    },
+  ],
+}
+`;

qlty-plugins/plugins/linters/stylelint/fixtures/extends.in/.qlty/qlty.toml

@@ -0,0 +1,12 @@
+config_version = "0"
+
+[[source]]
+name = "default"
+default = true
+
+[[plugin]]
+name = "stylelint"
+version = "17.3.0"
+package_file = "package.json"
+package_filters = ["stylelint"]
+config_files = [".stylelintrc.json"]

qlty-plugins/plugins/linters/stylelint/fixtures/extends.in/.stylelintrc.json

@@ -0,0 +1,3 @@
+{
+  "extends": ["stylelint-config-standard"]
+}

qlty-plugins/plugins/linters/stylelint/fixtures/extends.in/basic.in.css

@@ -0,0 +1 @@
+a {}

qlty-plugins/plugins/linters/stylelint/fixtures/extends.in/package.json

@@ -0,0 +1,9 @@
+{
+  "name": "stylelint-extends-fixture",
+  "version": "0.0.0",
+  "private": true,
+  "devDependencies": {
+    "stylelint": "17.3.0",
+    "stylelint-config-standard": "39.0.0"
+  }
+}

qlty-plugins/plugins/linters/stylelint/plugin.toml

@@ -34,7 +34,7 @@ package_file_candidate_filters = ["stylelint"]
 
 [[plugins.definitions.stylelint.drivers.lint.version]]
 version_matcher = "<16.0.0"
-script = "stylelint --formatter json ${target}"
+script = 'stylelint --config-basedir "${linter}" --formatter json ${target}'
 success_codes = [0, 2]
 error_codes = [1, 78]
 output = "stdout"
@@ -47,7 +47,7 @@ output_missing = "error"
 
 [[plugins.definitions.stylelint.drivers.lint.version]]
 version_matcher = ">=16.0.0"
-script = "stylelint --formatter json ${target}"
+script = 'stylelint --config-basedir "${linter}" --formatter json ${target}'
 success_codes = [0, 2]
 error_codes = [1, 78]
 output = "stderr"
@@ -59,7 +59,7 @@ suggested = "config"
 output_missing = "error"
 
 [plugins.definitions.stylelint.drivers.format]
-script = "stylelint --fix ${target}"
+script = 'stylelint --config-basedir "${linter}" --fix ${target}'
 success_codes = [0, 2]
 error_codes = [1, 78]
 cache_results = true