[POC] oxlint - with scripts

.github/workflows/oxlint.yml

@@ -0,0 +1,72 @@
+name: Oxlint check (non-blocking)
+
+on:
+  workflow_call:
+  pull_request:
+    types: [opened, synchronize]
+    branches-ignore: [staging, production]
+    paths: ['**.js', '**.ts', '**.tsx', '**.json', '**.mjs', '**.cjs', 'oxlint.config.mts', 'config/oxlint/**', 'scripts/lint/**', '.github/workflows/oxlint.yml']
+
+concurrency:
+  group: ${{ github.ref == 'refs/heads/main' && format('{0}-{1}', github.ref, github.sha) || github.ref }}-oxlint
+  cancel-in-progress: true
+
+jobs:
+  oxlint:
+    name: Oxlint check (non-blocking)
+    if: ${{ github.event.head_commit.author.name != 'OSBotify' || github.event_name == 'push' }}
+    runs-on: blacksmith-8vcpu-ubuntu-2404
+    steps:
+      - name: Checkout
+        uses: useblacksmith/checkout@0647fdbab2614a5eb86d2971070e325060d91056 # v1.7.0
+        with:
+          token: ${{ github.event_name == 'push' && secrets.OS_BOTIFY_COMMIT_TOKEN || github.token }}
+
+      - name: Setup Node
+        uses: ./.github/actions/composite/setupNode
+
+      - name: Lint JavaScript and TypeScript with Oxlint
+        id: oxlint
+        continue-on-error: true
+        # oxlint runs JS plugins on one thread (oxc#26621), so OxlintLinter splits them into 4 shards on this 8 vCPU runner.
+        # While oxlint is a non-blocking check, the post-merge run both adds and removes entries from the oxlint.seatbelt.tsv.
+        # Remove this once oxlint becomes the blocking linter.
+        env:
+          SEATBELT_INCREASE: ${{ github.event_name == 'push' && github.event.head_commit.author.name != 'OSBotify' && 'all' || '' }}
+        run: npm run lint -- --linter=oxlint --shards=4
+
+      - name: Check for an updated oxlint-seatbelt baseline
+        id: seatbelt_diff
+        if: github.event_name == 'push'
+        run: |
+          if git diff --quiet config/oxlint/oxlint.seatbelt.tsv; then
+            echo "updated=false" >> "$GITHUB_OUTPUT"
+          else
+            echo "updated=true" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Report the Oxlint result without failing the job
+        run: |
+          if [[ "${{ steps.oxlint.outcome }}" != "success" ]]; then
+            echo "::warning::Oxlint found errors this PR adds (see the step log). This check is temporarily non-blocking while oxlint runs next to ESLint."
+          elif [[ "${{ steps.seatbelt_diff.outputs.updated }}" == "true" ]]; then
+            echo "::notice::This merge changed the list of known oxlint errors (config/oxlint/oxlint.seatbelt.tsv). OSBotify commits the update. Temporary while oxlint runs next to ESLint."
+          else
+            echo "::notice::Oxlint found no new errors."
+          fi
+
+      - name: Setup git for OSBotify
+        if: steps.seatbelt_diff.outputs.updated == 'true'
+        uses: Expensify/GitHub-Actions/setupGitForOSBotify@main
+        with:
+          OP_VAULT: ${{ vars.OP_VAULT }}
+          OP_SERVICE_ACCOUNT_TOKEN: ${{ secrets.OP_SERVICE_ACCOUNT_TOKEN }}
+          SETUP_AS_APP: false
+
+      - name: Auto-commit updated oxlint-seatbelt baseline
+        if: steps.seatbelt_diff.outputs.updated == 'true'
+        continue-on-error: true
+        run: |
+          git add config/oxlint/oxlint.seatbelt.tsv
+          git commit -m "Auto-update oxlint-seatbelt baseline"
+          git push origin main

.github/workflows/preDeploy.yml

@@ -14,6 +14,11 @@ jobs:
     uses: ./.github/workflows/lint.yml
     secrets: inherit
 
+  # Left out of confirmPassingBuild's `needs` on purpose: Oxlint is a shadow gate that runs here to auto-tighten its baseline.
+  oxlint:
+    uses: ./.github/workflows/oxlint.yml
+    secrets: inherit
+
   oxfmt:
     uses: ./.github/workflows/oxfmt.yml
 

.gitignore

@@ -185,3 +185,19 @@ server/victory-chart-renderer/.dev/
 
 # Bun lockfiles (VCR uses npm workspaces + package-lock.json; bun is runtime-only)
 bun.lock
+
+# Oxlint migration investigation: generated rule inventory (npm run oxlint-rule-inventory)
+oxlint-migration/rule-inventory.json
+oxlint-migration/rule-availability.json
+
+# Oxlint migration investigation: raw no-deprecated report dumps from the obstacle #4 probe
+oxlint-migration/dep-cmp.json
+oxlint-migration/dep-only-api.json
+
+# Python caches from the oxlint-migration comparison scripts
+__pycache__/
+oxlint-migration/port-probe/oxlint.fixtures.merged*.json
+
+# Per-run Oxlint configs written by scripts/lint/oxlint/OxlintLinter.ts
+.oxlintrc.js-plugins.*.json
+.oxlintrc.type-aware.*.json

.npmrc

@@ -10,3 +10,8 @@ min-release-age-exclude[]=@expensify/react-native-wallet
 min-release-age-exclude[]=react-fast-pdf
 min-release-age-exclude[]=react-native-key-command
 min-release-age-exclude[]=react-native-qrcode-svg
+# List each native binding scope too, or npm silently skips the optional dependency.
+min-release-age-exclude[]=oxlint
+min-release-age-exclude[]=@oxlint/*
+min-release-age-exclude[]=oxc-transform-react
+min-release-age-exclude[]=@oxc-transform-react/*

.oxfmtrc.json

@@ -72,7 +72,8 @@
         "src/libs/SearchParser/searchParser.js",
         "src/libs/SearchParser/autocompleteParser.js",
         "Mobile-Expensify",
-        "modules/group-ib-fp"
+        "modules/group-ib-fp",
+        "oxlint-migration/port-probe/fixtures"
     ],
     "overrides": [
         {

config/eslint/eslint.config.mjs

@@ -833,6 +833,12 @@ const config = defineConfig([
     globalIgnores([
         '!**/.storybook',
         '!**/.github',
+        // Oxlint migration harness, deleted with ESLint (see oxlint-migration/README.md).
+        // config/oxlint/ is deliberately NOT ignored: it is production lint config, not an artifact.
+        'oxlint-migration/**',
+        // Conductor scratch directory, gitignored. Oxlint already skips it, so ESLint has to as
+        // well or the two legs lint different file sets.
+        '.context/**',
         '.github/actions/**/index.js',
         '**/*.config.js',
         '**/*.config.mjs',

config/oxlint/eslintDirectives.mjs

@@ -0,0 +1,176 @@
+/**
+ * oxlint runs some ESLint rules as JS plugins under a new name. For example,
+ * `@typescript-eslint/naming-convention` becomes `hosted/naming-convention`. oxlint doesn't know the
+ * two are the same rule, so an existing `eslint-disable-next-line @typescript-eslint/naming-convention`
+ * comment wouldn't hide its report. The wrappers here read those comments and drop what ESLint would hide.
+ */
+
+const JUSTIFICATION = /\s-{2,}\s/;
+const KINDS = ['eslint-disable-next-line', 'eslint-disable-line', 'eslint-disable', 'eslint-enable'];
+const ALL_RULES = ' all';
+
+const cache = new Map();
+
+/**
+ * Turns a comment like `eslint-disable-next-line rule-a, rule-b -- reason` into its kind and the rules
+ * it names. A directive that names no rule applies to every rule.
+ * @param {{type: 'Line' | 'Block', value: string, loc?: {start: {line: number, column: number}, end: {line: number, column: number}}}} comment
+ * @returns {{kind: string, ruleIds: string[]} | null} null when the comment is not a directive
+ */
+function parseComment(comment) {
+    const text = String(comment.value ?? '').trim();
+    const kind = KINDS.find((candidate) => text === candidate || (text.startsWith(candidate) && /^\s/.test(text.slice(candidate.length))));
+    if (!kind) {
+        return null;
+    }
+    const body = text.slice(kind.length).split(JUSTIFICATION)[0];
+    const ruleIds = body
+        .split(',')
+        .map((id) => id.trim())
+        .filter(Boolean);
+    return {kind, ruleIds: ruleIds.length ? ruleIds : [ALL_RULES]};
+}
+
+/**
+ * Collects a file's disable comments in a form that is quick to check for each report. A
+ * `-line`/`-next-line` comment becomes the line it covers. `eslint-disable`/`eslint-enable` comments
+ * stay in source order, because the last one before a report decides.
+ * @param {Array<Parameters<typeof parseComment>[0]>} comments
+ * @returns {{lines: Map<string, Set<number>>, blocks: Array<{line: number, column: number, ruleId: string, disable: boolean}>}}
+ */
+function parseDirectives(comments) {
+    const lines = new Map();
+    const blocks = [];
+
+    for (const comment of comments) {
+        const parsed = parseComment(comment);
+        const start = comment.loc?.start?.line;
+        const end = comment.loc?.end?.line;
+        if (!parsed || start == null || end == null) {
+            continue;
+        }
+        // ESLint reads `eslint-disable` and `eslint-enable` only from block comments.
+        const isBlockKind = parsed.kind === 'eslint-disable' || parsed.kind === 'eslint-enable';
+        if (isBlockKind && comment.type !== 'Block') {
+            continue;
+        }
+        for (const ruleId of parsed.ruleIds) {
+            if (parsed.kind === 'eslint-disable-next-line' || parsed.kind === 'eslint-disable-line') {
+                // ESLint ignores a multi-line `-line` directive but applies a multi-line `-next-line`
+                // to the line after the comment ends.
+                if (parsed.kind === 'eslint-disable-line' && start !== end) {
+                    continue;
+                }
+                if (!lines.has(ruleId)) {
+                    lines.set(ruleId, new Set());
+                }
+                lines.get(ruleId).add(parsed.kind === 'eslint-disable-line' ? start : end + 1);
+            } else {
+                blocks.push({line: start, column: comment.loc.start.column ?? 0, ruleId, disable: parsed.kind === 'eslint-disable'});
+            }
+        }
+    }
+
+    return {lines, blocks};
+}
+
+/**
+ * Every wrapped rule checks the same file's comments, so they are parsed once per file.
+ * @param {string | undefined} filename
+ * @param {Array<Parameters<typeof parseComment>[0]>} comments
+ * @returns {ReturnType<typeof parseDirectives>}
+ */
+function directivesFor(filename, comments) {
+    const key = filename ?? '<unknown>';
+    if (!cache.has(key)) {
+        cache.set(key, parseDirectives(comments));
+    }
+    return cache.get(key);
+}
+
+/**
+ * Tells whether ESLint would hide a report of `eslintRuleId` at `position`. As in ESLint, the last
+ * `eslint-disable`/`eslint-enable` before the report, by line and then column, that names the rule
+ * (or no rule) wins.
+ * @param {ReturnType<typeof parseDirectives>} directives
+ * @param {string} eslintRuleId
+ * @param {{line: number, column: number} | null} position
+ * @returns {boolean}
+ */
+function isSuppressed(directives, eslintRuleId, position) {
+    if (position == null) {
+        return false;
+    }
+    const {line, column} = position;
+    if (directives.lines.get(eslintRuleId)?.has(line) || directives.lines.get(ALL_RULES)?.has(line)) {
+        return true;
+    }
+    let disabled = false;
+    for (const block of directives.blocks) {
+        const isAfterReport = block.line > line || (block.line === line && block.column > column);
+        if (isAfterReport || (block.ruleId !== ALL_RULES && block.ruleId !== eslintRuleId)) {
+            continue;
+        }
+        disabled = block.disable;
+    }
+    return disabled;
+}
+
+/**
+ * Finds the line and column a report points at, to check it against the disable comments. Rules pass
+ * either a descriptor with `loc` or `node`, or a node in the legacy `report(node, message)` form.
+ * @param {unknown[]} args
+ * @returns {{line: number, column: number} | null}
+ */
+function reportPosition(args) {
+    const first = args[0];
+    const candidates = [first?.loc?.start, first?.loc, first?.node?.loc?.start, first?.node?.loc];
+    const point = candidates.find((candidate) => typeof candidate?.line === 'number');
+    return point ? {line: point.line, column: typeof point.column === 'number' ? point.column : 0} : null;
+}
+
+/**
+ * Makes an oxlint JS plugin rule respect `eslint-disable` comments written for the ESLint rule it
+ * copies. Without it, `// eslint-disable-next-line react-hooks/exhaustive-deps` would not hide the
+ * oxlint copy's report, because oxlint calls that copy `hosted/exhaustive-deps`.
+ * @param {import('eslint').Rule.RuleModule} rule
+ * @param {string} eslintRuleId the ID ESLint reports this rule under, like `react-hooks/exhaustive-deps`
+ * @returns {import('eslint').Rule.RuleModule}
+ */
+function withEslintDirectiveIDs(rule, eslintRuleId) {
+    return {
+        ...rule,
+        create(context) {
+            const filteredContext = Object.create(context, {
+                report: {
+                    // Keeps every argument: ESLint also accepts the legacy `report(node, message)` form.
+                    value(...args) {
+                        const position = reportPosition(args);
+                        if (position != null) {
+                            const sourceCode = context.sourceCode ?? context.getSourceCode();
+                            const filename = context.filename ?? context.getFilename();
+                            if (isSuppressed(directivesFor(filename, sourceCode.getAllComments()), eslintRuleId, position)) {
+                                return;
+                            }
+                        }
+                        return context.report(...args);
+                    },
+                },
+            });
+            return rule.create(filteredContext);
+        },
+    };
+}
+
+/**
+ * withEslintDirectiveIDs for a whole plugin at once. `toEslintId` gives the ESLint name of each rule,
+ * like `naming-convention` to `@typescript-eslint/naming-convention`.
+ * @param {Record<string, import('eslint').Rule.RuleModule>} rules
+ * @param {(name: string) => string} toEslintId maps an oxlint rule name to its ESLint ID
+ * @returns {Record<string, import('eslint').Rule.RuleModule>}
+ */
+function withEslintDirectiveIDsFor(rules, toEslintId) {
+    return Object.fromEntries(Object.entries(rules).map(([name, rule]) => [name, withEslintDirectiveIDs(rule, toEslintId(name))]));
+}
+
+export {withEslintDirectiveIDs, withEslintDirectiveIDsFor};