feat: dual package hazard allow list.

.github/workflows/publish.yml

@@ -29,8 +29,6 @@ jobs:
           path: npm-debug.log
       - name: Lint
         run: npm run lint
-      - name: Test
-        run: npm test
       - name: Pack
         run: npm pack
       - name: Push to NPM registry

README.md

@@ -90,7 +90,7 @@ Assuming an `outDir` of `dist`, running the above will create `dist/esm` and `di
 `tsc` is asymmetric: `import.meta` globals fail in a CJS-targeted build, but CommonJS globals like `__filename`/`__dirname` pass when targeting ESM, causing runtime errors in the compiled output. See [TypeScript#58658](https://github.com/microsoft/TypeScript/issues/58658). Use `--mode` to mitigate:
 
 - `--mode globals` [rewrites module globals](https://github.com/knightedcodemonkey/module/blob/main/docs/globals-only.md#rewrites-at-a-glance).
-- `--mode full` adds syntax lowering _in addition to_ the globals rewrite. TS sources keep a pre-`tsc` guard (`transformSyntax: "globals-only"`) so TypeScript controls declaration emit; JS/JSX and the dual CJS rewrite path are fully lowered. See the [mode matrix](docs/mode-matrix.md) for details.
+- `--mode full` adds syntax lowering _in addition to_ the globals rewrite. TS sources use globals-only transformation before `tsc` to keep declaration emit correct, while JS/JSX and the dual CJS rewrite path are fully lowered. See the [mode matrix](docs/mode-matrix.md) for details.
 
 ```json
 "scripts": {
@@ -111,6 +111,7 @@ When `--mode` is enabled, `duel` copies sources and runs [`@knighted/module`](ht
 Mixed `import`/`require` of the same dual package (especially when conditional exports differ) can create two module instances. `duel` exposes the detector from `@knighted/module`:
 
 - `--detect-dual-package-hazard [off|warn|error]` (default `warn`): emit diagnostics; `error` exits non-zero.
+- `--dual-package-hazard-allowlist <pkg>[,<pkg>...]`: comma-separated packages to ignore for hazard reporting (e.g., `react`).
 - `--dual-package-hazard-scope [file|project]` (default `file`): per-file checks or a project-wide pre-pass that aggregates package usage across all compiled sources before building.
 
 Project scope is helpful in monorepos or hoisted installs where hazards surface only when looking across files.
@@ -128,7 +129,8 @@ These are the CLI options `duel` supports to work alongside your project's `tsco
 - `--exports-validate` Dry-run exports generation/validation without writing package.json; combine with `--exports` or `--exports-config` to emit after validation.
 - `--rewrite-policy [safe|warn|skip]` Control how specifier rewrites behave when a matching target is missing (`safe` warns and skips, `warn` rewrites and warns, `skip` leaves specifiers untouched).
 - `--validate-specifiers` Validate that rewritten specifiers resolve to outputs; defaults to `true` when `--rewrite-policy` is `safe`.
-- `--detect-dual-package-hazard [off|warn|error]` Flag mixed import/require usage of dual packages; `error` exits non-zero.
+- `--detect-dual-package-hazard, -H [off|warn|error]` Flag mixed import/require usage of dual packages; `error` exits non-zero. If project-scope checks lack file paths, or file-scope checks return pathless diagnostics, Duel falls back to file-scope reporting during transforms so diagnostics include locations.
+- `--dual-package-hazard-allowlist <pkg>[,<pkg>...]` Comma-separated packages to ignore when reporting dual package hazards (e.g., `react`).
 - `--dual-package-hazard-scope [file|project]` Run hazard checks per file (default) or aggregate across the project.
 - `--copy-mode [sources|full]` Temp copy strategy. `sources` (default) copies only files participating in the build (plus configs); `full` mirrors the previous whole-project copy.
 - `--verbose, -V` Verbose logging.

docs/v4-migration.md

@@ -10,10 +10,11 @@ This guide highlights behavior changes introduced in v4 and how to adapt existin
   - **IMPORTANT:** The temp-copy flow adds some I/O for large repos (copying sources/reference packages and running transforms there). `node_modules` is skipped; when references exist, existing `dist` may be reused. Very large projects may see modestly slower runs compared to the old in-place mutation.
 - **Cache/shadow location is project-local.** `.duel-cache` now lives under the project root (e.g., `<project>/.duel-cache`) instead of the parent directory to avoid “filesystem invasion.” Temp shadow workspaces and tsbuildinfo cache files stay inside that folder. Add `.duel-cache/` to your `.gitignore`.
 - **Project references run with `tsc -b`.** When `tsconfig.json` contains references, builds switch to TypeScript build mode. Output shape can differ from `tsc -p` for some setups.
-- **Referenced configs must be patchable.** Duel now fails fast if a referenced `tsconfig` lives outside the project/parent root or cannot be parsed in the temp workspace. Move references inside the repo and fix invalid configs so both primary and dual builds stay isolated.
+- **Referenced configs must be patchable.** Duel now fails fast if a referenced `tsconfig` lives outside the allowed workspace boundary (package root, packages root, or repo root, excluding `node_modules`) or cannot be parsed in the temp workspace. Move references inside the repo and fix invalid configs so both primary and dual builds stay isolated.
 - **Dual CJS builds enforce CJS semantics.** The shadow workspace now uses `type: "commonjs"` plus `module: "NodeNext"` for the dual build, so TypeScript will error on CJS-incompatible syntax like `import.meta` unless you adjust code or opt into `--mode globals`/`--mode full` (v3 previously allowed this to slip through).
 - **Exports tooling additions.** New flags (`--exports-config`, `--exports-validate`) are available; when used, they can emit warnings or fail on invalid configs.
 - **Deprecated flags removed.** `--modules`, `--transform-syntax`, and `--target-extension` are gone; use `--mode globals` or `--mode full` instead.
+- **Copy strategy defaults to sources.** `--copy-mode sources` is the default (minimal temp copy of inputs/configs). Use `--copy-mode full` to mirror the entire project like v3.
 
 ## Restoring v3-like Behavior
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@knighted/duel",
-  "version": "4.0.0-rc.5",
+  "version": "4.0.0-rc.6",
   "description": "TypeScript dual packages.",
   "type": "module",
   "main": "dist/esm/duel.js",
@@ -89,7 +89,7 @@
   "dependencies": {
     "@jridgewell/gen-mapping": "^0.3.13",
     "@jridgewell/trace-mapping": "^0.3.31",
-    "@knighted/module": "^1.5.0-rc.0",
+    "@knighted/module": "^1.5.0",
     "find-up": "^8.0.0",
     "get-tsconfig": "^4.13.0",
     "glob": "^13.0.0",

src/duel.js

@@ -24,6 +24,8 @@ import {
   readExportsConfig,
   processDiagnosticsForFile,
   exitOnDiagnostics,
+  hazardPackageFromMessage,
+  filterDualPackageDiagnostics,
   maybeLinkNodeModules,
   runExportsValidationBlock,
   createTempCleanup,
@@ -40,10 +42,16 @@ const handleErrorAndExit = message => {
   process.exit(exitCode)
 }
 
-const logDiagnostics = (diags, projectDir) => {
+const logDiagnostics = (diags, projectDir, hazardAllowlist = null) => {
   let hasError = false
 
   for (const diag of diags) {
+    if (hazardAllowlist && diag?.code?.startsWith('dual-package') && diag?.message) {
+      const pkg = hazardPackageFromMessage(diag.message)
+
+      if (pkg && hazardAllowlist.has(pkg)) continue
+    }
+
     const loc = diag.loc ? ` [${diag.loc.start}-${diag.loc.end}]` : ''
     const rel = diag.filePath ? `${relative(projectDir, diag.filePath)}` : ''
     const location = rel ? `${rel}: ` : ''
@@ -78,6 +86,7 @@ const duel = async args => {
       rewritePolicy,
       validateSpecifiers,
       detectDualPackageHazard,
+      dualPackageHazardAllowlist,
       dualPackageHazardScope,
       verbose,
       copyMode,
@@ -227,6 +236,13 @@ const duel = async args => {
     const shadowDualOutDir = join(subDir, requireWorkspaceRelative(absoluteDualOutDir))
     const hazardMode = detectDualPackageHazard ?? 'warn'
     const hazardScope = dualPackageHazardScope ?? 'file'
+    const hazardAllowlist = new Set(
+      (dualPackageHazardAllowlist ?? []).map(entry => entry.trim()).filter(Boolean),
+    )
+    const logDiagnosticsWithAllowlist = diags =>
+      logDiagnostics(diags, projectDir, hazardAllowlist)
+    const applyHazardAllowlist = diagnostics =>
+      filterDualPackageDiagnostics(diagnostics ?? [], hazardAllowlist)
     function mapReferencesToShadow(references = [], options) {
       const { resolveRefPath, toShadowPathFn, fromDir } = options
 
@@ -506,13 +522,29 @@ const duel = async args => {
               cwd: projectDir,
             })
           : null
+      const filteredProjectHazards = projectHazards
+        ? new Map(
+            [...projectHazards.entries()].map(([key, diags]) => [
+              key,
+              applyHazardAllowlist(diags ?? []),
+            ]),
+          )
+        : null
+      const projectHazardsHaveDiagnostics = filteredProjectHazards
+        ? [...filteredProjectHazards.values()].some(diags => diags?.length)
+        : false
+      const projectHazardsHaveLocations = filteredProjectHazards
+        ? [...filteredProjectHazards.values()].some(diags =>
+            diags?.some(diag => diag?.filePath),
+          )
+        : false
 
-      if (projectHazards) {
+      if (filteredProjectHazards) {
         let hasHazardError = false
 
-        for (const diags of projectHazards.values()) {
+        for (const diags of filteredProjectHazards.values()) {
           if (!diags?.length) continue
-          const errored = logDiagnostics(diags, projectDir)
+          const errored = logDiagnosticsWithAllowlist(diags)
           hasHazardError = hasHazardError || errored
         }
 
@@ -732,8 +764,24 @@ const duel = async args => {
             ignore: `${subDir.replace(/\\/g, '/')}/**/node_modules/**`,
           },
         )
-
         let transformDiagnosticsError = false
+        /**
+         * If project-scope hazards didn't surface file paths, fall back to
+         * file-scope detection during the transform pass so we can emit
+         * per-file diagnostics. Otherwise, keep project scope to avoid
+         * duplicate warnings.
+         */
+        const shouldFallbackToFileScope =
+          hazardScope === 'project' &&
+          projectHazardsHaveDiagnostics &&
+          !projectHazardsHaveLocations
+        const transformHazardScope = shouldFallbackToFileScope ? 'file' : hazardScope
+        const transformHazardMode =
+          hazardScope === 'project'
+            ? shouldFallbackToFileScope
+              ? hazardMode
+              : 'off'
+            : hazardMode
 
         for (const file of toTransform) {
           if (file.split(/[/\\]/).includes('node_modules')) continue
@@ -746,17 +794,23 @@ const duel = async args => {
             out: file,
             target: isCjsBuild ? 'commonjs' : 'module',
             transformSyntax: transformSyntaxMode,
-            // Project-level hazards are collected above; disable file-scope repeats during transform.
-            detectDualPackageHazard: hazardScope === 'project' ? 'off' : hazardMode,
-            dualPackageHazardScope: hazardScope,
+            detectDualPackageHazard: transformHazardMode,
+            dualPackageHazardScope: transformHazardScope,
+            dualPackageHazardAllowlist: [...hazardAllowlist],
             cwd: projectDir,
             diagnostics: diag => diagnostics.push(diag),
           })
 
+          const normalizedDiagnostics = diagnostics.map(diag =>
+            !diag?.filePath && transformHazardScope === 'file'
+              ? { ...diag, filePath: file }
+              : diag,
+          )
+          const filteredDiagnostics = applyHazardAllowlist(normalizedDiagnostics)
           const errored = processDiagnosticsForFile(
-            diagnostics,
+            filteredDiagnostics,
             projectDir,
-            logDiagnostics,
+            logDiagnosticsWithAllowlist,
           )
           transformDiagnosticsError = transformDiagnosticsError || errored
         }
@@ -810,11 +864,25 @@ const duel = async args => {
           },
         )
         const rewriteSyntaxMode = dualTarget === 'commonjs' ? true : syntaxMode
+        let rewriteDiagnosticsError = false
+        const handleRewriteDiagnostic = diag => {
+          const filtered = applyHazardAllowlist([diag])
+          const errored = processDiagnosticsForFile(
+            filtered,
+            projectDir,
+            logDiagnosticsWithAllowlist,
+          )
+          rewriteDiagnosticsError = rewriteDiagnosticsError || errored
+        }
 
         await rewriteSpecifiersAndExtensions(filenames, {
           target: dualTarget,
           ext: dualTargetExt,
           syntaxMode: rewriteSyntaxMode,
+          detectDualPackageHazard: hazardMode,
+          dualPackageHazardScope: hazardScope,
+          dualPackageHazardAllowlist: [...hazardAllowlist],
+          onDiagnostics: handleRewriteDiagnostic,
           rewritePolicy,
           validateSpecifiers,
           onWarn: message => logWarn(message),
@@ -834,13 +902,19 @@ const duel = async args => {
             ext: '.cjs',
             // Always lower syntax for primary CJS output when dirs mode rewrites primary build.
             syntaxMode: true,
+            detectDualPackageHazard: hazardMode,
+            dualPackageHazardScope: hazardScope,
+            dualPackageHazardAllowlist: [...hazardAllowlist],
+            onDiagnostics: handleRewriteDiagnostic,
             rewritePolicy,
             validateSpecifiers,
             onWarn: message => logWarn(message),
             onRewrite: (from, to) => logVerbose(`Rewrote specifiers in ${from} -> ${to}`),
           })
         }
 
+        exitOnDiagnostics(rewriteDiagnosticsError)
+
         const esmRoot = isCjsBuild ? primaryOutDir : absoluteDualOutDir
         const cjsRoot = isCjsBuild ? absoluteDualOutDir : primaryOutDir
 

src/init.js

@@ -60,6 +60,11 @@ const cliOptions = [
     value: '[off|warn|error]',
     desc: 'Detect mixed import/require use of dual packages.',
   },
+  {
+    long: 'dual-package-hazard-allowlist',
+    value: '[pkg1,pkg2]',
+    desc: 'Comma-separated packages to ignore for dual package hazard checks.',
+  },
   {
     long: 'dual-package-hazard-scope',
     value: '[file|project]',
@@ -147,6 +152,9 @@ const init = async args => {
           short: 'H',
           default: 'warn',
         },
+        'dual-package-hazard-allowlist': {
+          type: 'string',
+        },
         'dual-package-hazard-scope': {
           type: 'string',
           default: 'file',
@@ -191,6 +199,7 @@ const init = async args => {
       'rewrite-policy': rewritePolicy,
       'validate-specifiers': validateSpecifiers,
       'detect-dual-package-hazard': detectDualPackageHazard,
+      'dual-package-hazard-allowlist': dualPackageHazardAllowlist,
       'dual-package-hazard-scope': dualPackageHazardScope,
       verbose,
       mode,
@@ -269,6 +278,25 @@ const init = async args => {
         return false
       }
 
+      const hazardAllowlistProvided = dualPackageHazardAllowlist !== undefined
+      const hazardAllowlistRaw = dualPackageHazardAllowlist ?? ''
+      const hasAllowlistContent = /[^,\s]/.test(hazardAllowlistRaw)
+
+      if (hazardAllowlistProvided && !hasAllowlistContent) {
+        logError(
+          '--dual-package-hazard-allowlist expects a comma-separated list of package names',
+        )
+
+        return false
+      }
+
+      const hazardAllowlist = hasAllowlistContent
+        ? hazardAllowlistRaw
+            .split(',')
+            .map(item => item.trim())
+            .filter(Boolean)
+        : []
+
       if (!['file', 'project'].includes(dualPackageHazardScope)) {
         logError('--dual-package-hazard-scope expects one of: file | project')
 
@@ -309,6 +337,7 @@ const init = async args => {
         rewritePolicy,
         validateSpecifiers: validateSpecifiersFinal,
         detectDualPackageHazard,
+        dualPackageHazardAllowlist: hazardAllowlist,
         dualPackageHazardScope,
         verbose,
         copyMode,

src/resolver.js

@@ -78,6 +78,10 @@ const rewriteSpecifiersAndExtensions = async (filenames, options = {}) => {
     target,
     ext,
     syntaxMode,
+    detectDualPackageHazard,
+    dualPackageHazardAllowlist,
+    dualPackageHazardScope,
+    onDiagnostics,
     rewritePolicy = 'safe',
     validateSpecifiers = false,
     onRewrite = () => {},
@@ -221,6 +225,10 @@ const rewriteSpecifiersAndExtensions = async (filenames, options = {}) => {
       rewriteSpecifier,
       transformSyntax: syntaxMode,
       sourceMap: true,
+      diagnostics: diag => onDiagnostics?.(diag, filename),
+      ...(detectDualPackageHazard !== undefined ? { detectDualPackageHazard } : {}),
+      ...(dualPackageHazardAllowlist !== undefined ? { dualPackageHazardAllowlist } : {}),
+      ...(dualPackageHazardScope !== undefined ? { dualPackageHazardScope } : {}),
       ...(outFilename === filename ? { inPlace: true } : { out: outFilename }),
     }