fix(migrate): treat any two Oxc configs in a directory as a conflict

The conflict guard fired only when a directory held a JSON *and* a dynamic
config for the same tool. Running the pinned binaries shows the rule both
tools enforce is one config per directory, not one config form: oxlint
1.78.0 and oxfmt 0.63.0 each fail with "Both '<a>' and '<b>' found in
<dir>" for `.oxlintrc.json` + `.oxlintrc.jsonc` and for
`oxlint.config.ts` + `oxlint.config.mts`, exactly as they do for the mixed
pair. Both of those shapes previously migrated through, consuming one
config and leaving the other on disk unreferenced.

Detection now flags any tool with more than one config present, and the
conflict carries a single `configs` list in the tool's candidate order
instead of the JSON/dynamic split. The rendered line is unchanged for the
two-config case and gains comma separation beyond it.

Author: m0g3r

packages/cli/src/migration/__tests__/detector.spec.ts

@@ -84,28 +84,25 @@ describe('detectOxcConfigConflicts', () => {
     expect(detectOxcConfigConflicts(tmpDir)).toEqual([]);
   });
 
-  // Two JSON forms are deliberately NOT a conflict here: the ambiguity this
-  // guard exists for is JSON-vs-dynamic, which is the combination oxlint itself
-  // rejects and the one that leaves an unreferenced config shadowing the
-  // inlined block after migration.
-  it('reports no conflict for two JSON forms of the same tool', () => {
-    write('.oxlintrc.json');
-    write('.oxlintrc.jsonc');
-
-    expect(detectOxcConfigConflicts(tmpDir)).toEqual([]);
-  });
-
+  // The rule both tools enforce is one config per directory, not one config
+  // *form*: `.oxlintrc.json` + `.oxlintrc.jsonc` and `oxlint.config.ts` +
+  // `oxlint.config.mts` fail the same way the mixed pair does, so every
+  // two-config shape below is a conflict.
   it.each([
     ['oxlint', '.oxlintrc.json', 'oxlint.config.ts'],
     ['oxlint', '.oxlintrc.jsonc', 'oxlint.config.mts'],
+    ['oxlint', '.oxlintrc.json', '.oxlintrc.jsonc'],
+    ['oxlint', 'oxlint.config.ts', 'oxlint.config.mts'],
     ['oxfmt', '.oxfmtrc.json', 'oxfmt.config.ts'],
     ['oxfmt', '.oxfmtrc.jsonc', 'oxfmt.config.mts'],
-  ] as const)('flags %s when %s and %s coexist', (tool, jsonConfig, dynamicConfig) => {
-    write(jsonConfig);
-    write(dynamicConfig);
+    ['oxfmt', '.oxfmtrc.json', '.oxfmtrc.jsonc'],
+    ['oxfmt', 'oxfmt.config.ts', 'oxfmt.config.mts'],
+  ] as const)('flags %s when %s and %s coexist', (tool, firstConfig, secondConfig) => {
+    write(firstConfig);
+    write(secondConfig);
 
     expect(detectOxcConfigConflicts(tmpDir)).toEqual([
-      { tool, dir: '.', jsonConfigs: [jsonConfig], dynamicConfigs: [dynamicConfig] },
+      { tool, dir: '.', configs: [firstConfig, secondConfig] },
     ]);
   });
 
@@ -121,18 +118,17 @@ describe('detectOxcConfigConflicts', () => {
     ]);
   });
 
-  it('lists every present form on both sides of a conflict', () => {
-    write('.oxlintrc.json');
+  it('lists every config present, in the tool candidate order', () => {
+    write('oxlint.config.mts');
     write('.oxlintrc.jsonc');
     write('oxlint.config.ts');
-    write('oxlint.config.mts');
+    write('.oxlintrc.json');
 
     expect(detectOxcConfigConflicts(tmpDir)).toEqual([
       {
         tool: 'oxlint',
         dir: '.',
-        jsonConfigs: ['.oxlintrc.json', '.oxlintrc.jsonc'],
-        dynamicConfigs: ['oxlint.config.ts', 'oxlint.config.mts'],
+        configs: ['.oxlintrc.json', '.oxlintrc.jsonc', 'oxlint.config.ts', 'oxlint.config.mts'],
       },
     ]);
   });
@@ -145,8 +141,7 @@ describe('detectOxcConfigConflicts', () => {
       {
         tool: 'oxlint',
         dir: 'packages/app',
-        jsonConfigs: ['.oxlintrc.json'],
-        dynamicConfigs: ['oxlint.config.ts'],
+        configs: ['.oxlintrc.json', 'oxlint.config.ts'],
       },
     ]);
   });
@@ -188,8 +183,7 @@ describe('collectOxcConfigConflicts', () => {
       {
         tool: 'oxlint',
         dir: 'packages/app',
-        jsonConfigs: ['.oxlintrc.json'],
-        dynamicConfigs: ['oxlint.config.ts'],
+        configs: ['.oxlintrc.json', 'oxlint.config.ts'],
       },
     ]);
   });
@@ -225,8 +219,7 @@ describe('formatOxcConfigConflict', () => {
       formatOxcConfigConflict({
         tool: 'oxlint',
         dir: '.',
-        jsonConfigs: ['.oxlintrc.json'],
-        dynamicConfigs: ['oxlint.config.ts'],
+        configs: ['.oxlintrc.json', 'oxlint.config.ts'],
       }),
     ).toBe(
       'the project root has `.oxlintrc.json` and `oxlint.config.ts` — oxlint allows only one config per directory.',
@@ -238,11 +231,22 @@ describe('formatOxcConfigConflict', () => {
       formatOxcConfigConflict({
         tool: 'oxfmt',
         dir: 'packages/app',
-        jsonConfigs: ['.oxfmtrc.json'],
-        dynamicConfigs: ['oxfmt.config.mts'],
+        configs: ['.oxfmtrc.json', 'oxfmt.config.mts'],
       }),
     ).toBe(
       'packages/app has `.oxfmtrc.json` and `oxfmt.config.mts` — oxfmt allows only one config per directory.',
     );
   });
+
+  it('separates three or more configs with commas', () => {
+    expect(
+      formatOxcConfigConflict({
+        tool: 'oxlint',
+        dir: '.',
+        configs: ['.oxlintrc.json', '.oxlintrc.jsonc', 'oxlint.config.ts'],
+      }),
+    ).toBe(
+      'the project root has `.oxlintrc.json`, `.oxlintrc.jsonc` and `oxlint.config.ts` — oxlint allows only one config per directory.',
+    );
+  });
 });

packages/cli/src/migration/detector.ts

@@ -47,8 +47,8 @@ export const PRETTIER_CONFIG_FILES = [
 // The JSON forms are inlined into `vite.config.*` during migration and deleted;
 // the dynamic forms are preserved and imported instead. Detection takes the
 // first match in each list, so the two forms are ordered JSON-first only to keep
-// the historical precedence — `detectOxcConfigConflicts` rejects the ambiguous
-// state before that precedence can matter.
+// the historical precedence — `detectOxcConfigConflicts` rejects any directory
+// holding more than one of these before that precedence can matter.
 // https://oxc.rs/docs/guide/usage/linter/config.html#configuration-file-format
 export const OXLINT_JSON_CONFIG_FILES = ['.oxlintrc.json', '.oxlintrc.jsonc'] as const;
 export const OXLINT_DYNAMIC_CONFIG_FILES = ['oxlint.config.ts', 'oxlint.config.mts'] as const;
@@ -68,25 +68,25 @@ export const OXFMT_CONFIG_FILES = [
 export interface OxcConfigConflict {
   /** `oxlint` or `oxfmt` — the tool whose config is ambiguous. */
   tool: 'oxlint' | 'oxfmt';
-  /** Directory holding both forms, relative to the workspace root ('.' for the root). */
+  /** Directory holding the competing configs, relative to the workspace root ('.' for the root). */
   dir: string;
-  /** Every JSON-form config present in `dir`. */
-  jsonConfigs: string[];
-  /** Every dynamic-form config present in `dir`. */
-  dynamicConfigs: string[];
+  /** Every config for `tool` present in `dir`, in the tool's own candidate order. */
+  configs: string[];
 }
 
 /**
- * Detect directories that hold both a JSON and a dynamic config for the same Oxc
- * tool.
+ * Detect directories that hold more than one config for the same Oxc tool.
  *
- * Oxlint itself refuses to run in that state ("Only one of `.oxlintrc.json` and
- * `oxlint.config.ts` is allowed per directory"), so such a project is already
- * broken before migration sees it. Migration cannot repair it either: first-match
- * detection would inline and delete the JSON config and leave the dynamic one on
- * disk unreferenced, where it then silently shadows the freshly inlined `lint`
- * block for direct `oxlint` invocations. Erroring out and letting the user pick a
- * single config first is the only outcome that does not quietly lose settings.
+ * Both tools refuse to run in that state — `oxlint` and `oxfmt` each fail with
+ * "Both '<a>' and '<b>' found in <dir>" — so such a project is already broken
+ * before migration sees it. The rule is one config per directory, not one config
+ * *form*: two JSON forms (`.oxlintrc.json` + `.oxlintrc.jsonc`) and two dynamic
+ * forms (`oxlint.config.ts` + `oxlint.config.mts`) are rejected exactly like the
+ * mixed pair. Migration cannot repair any of them either: first-match detection
+ * would consume one config and leave the rest on disk unreferenced, where they
+ * then silently shadow the freshly inlined `lint` block for direct `oxlint`
+ * invocations. Erroring out and letting the user pick a single config first is
+ * the only outcome that does not quietly lose settings.
  *
  * `dir` is `'.'` for the workspace root; other values are workspace-relative
  * package paths with forward slashes.
@@ -98,27 +98,15 @@ export function detectOxcConfigConflicts(
   const conflicts: OxcConfigConflict[] = [];
 
   const tools = [
-    {
-      tool: 'oxlint',
-      jsonForms: OXLINT_JSON_CONFIG_FILES,
-      dynamicForms: OXLINT_DYNAMIC_CONFIG_FILES,
-    },
-    {
-      tool: 'oxfmt',
-      jsonForms: OXFMT_JSON_CONFIG_FILES,
-      dynamicForms: OXFMT_DYNAMIC_CONFIG_FILES,
-    },
+    { tool: 'oxlint', configFiles: OXLINT_CONFIG_FILES },
+    { tool: 'oxfmt', configFiles: OXFMT_CONFIG_FILES },
   ] as const;
 
-  for (const { tool, jsonForms, dynamicForms } of tools) {
-    const present = (candidates: readonly string[]) =>
-      candidates.filter((config) => fs.existsSync(path.join(projectPath, config)));
+  for (const { tool, configFiles } of tools) {
+    const configs = configFiles.filter((config) => fs.existsSync(path.join(projectPath, config)));
 
-    const jsonConfigs = present(jsonForms);
-    const dynamicConfigs = present(dynamicForms);
-
-    if (jsonConfigs.length > 0 && dynamicConfigs.length > 0) {
-      conflicts.push({ tool, dir: relativeDir, jsonConfigs, dynamicConfigs });
+    if (configs.length > 1) {
+      conflicts.push({ tool, dir: relativeDir, configs });
     }
   }
 
@@ -146,9 +134,9 @@ export function collectOxcConfigConflicts(
 /** Render one conflict as a user-facing line for the migration abort message. */
 export function formatOxcConfigConflict(conflict: OxcConfigConflict): string {
   const location = conflict.dir === '.' ? 'the project root' : conflict.dir;
-  const files = [...conflict.jsonConfigs, ...conflict.dynamicConfigs]
-    .map((file) => `\`${file}\``)
-    .join(' and ');
+  const quoted = conflict.configs.map((file) => `\`${file}\``);
+  // `a and b` for the common pair, `a, b and c` once a directory holds more.
+  const files = [quoted.slice(0, -1).join(', '), quoted.at(-1)].filter(Boolean).join(' and ');
   return `${location} has ${files} — ${conflict.tool} allows only one config per directory.`;
 }