fix(babel): suppress type errors when @types/babel__core is not installed

packages/babel/src/babelCompat.dummy.ts

@@ -0,0 +1,4 @@
+// oxlint-disable eslint-plugin-unicorn/no-empty-file
+
+// Empty file to emulate the case where `@babel/core` does not have types (pre v8)
+// and `@types/babel__core` is not installed.

packages/babel/src/babelCompat.ts

@@ -9,6 +9,14 @@ import * as babel from '@babel/core'
 // https://github.com/type-challenges/type-challenges/issues/29285
 type IsAny<T> = boolean extends (T extends never ? true : false) ? true : false
 
+/** **When using babel 7, install `@types/babel__core` to get proper types.** */
+type InputOptionsFallback = {
+  /** **When using babel 7, install `@types/babel__core` to get proper types.** */
+  plugins?: unknown[]
+  /** **When using babel 7, install `@types/babel__core` to get proper types.** */
+  presets?: unknown[]
+}
+
 // @ts-ignore -- InputOptions doesn't exist in Babel 7
 type InputOptions8 = babel.InputOptions
 // @ts-ignore -- PresetItem doesn't exist in Babel 7
@@ -25,7 +33,12 @@ type PluginObj<T> = babel.PluginObj<T>
 // @ts-ignore -- BabelFileResult doesn't exist in Babel 8
 type BabelFileResult = babel.BabelFileResult
 
-export type InputOptions = IsAny<InputOptions8> extends false ? InputOptions8 : TransformOptions
+export type InputOptions =
+  IsAny<InputOptions8> extends false
+    ? InputOptions8
+    : IsAny<TransformOptions> extends false
+      ? TransformOptions
+      : InputOptionsFallback
 export type PresetItem = IsAny<PresetItem8> extends false ? PresetItem8 : babel.PluginItem
 export type PluginObject<T = babel.PluginPass> =
   IsAny<PluginObject8<T>> extends false ? PluginObject8<T> : PluginObj<T>

packages/babel/src/babelCompat.typetest.ts

@@ -0,0 +1,9 @@
+import type { PluginOptions } from './options'
+
+export const _testPlugin: PluginOptions = {
+  plugins: ['some-plugin'],
+}
+
+export const _testPreset: PluginOptions = {
+  presets: ['some-preset'],
+}

packages/babel/src/options.ts

@@ -10,23 +10,25 @@ import {
 } from './rolldownPreset'
 import { filterMap } from './utils'
 
-export interface InnerTransformOptions extends Pick<
-  babel.InputOptions,
-  | 'assumptions'
-  | 'auxiliaryCommentAfter'
-  | 'auxiliaryCommentBefore'
-  | 'exclude'
-  | 'comments'
-  | 'compact'
-  | 'cwd'
-  | 'generatorOpts'
-  | 'include'
-  | 'parserOpts'
-  | 'plugins'
-  | 'retainLines'
-  | 'shouldPrintComment'
-  | 'targets'
-  | 'wrapPluginVisitorMethod'
+export interface InnerTransformOptions extends Partial<
+  Pick<
+    babel.InputOptions,
+    | 'assumptions'
+    | 'auxiliaryCommentAfter'
+    | 'auxiliaryCommentBefore'
+    | 'exclude'
+    | 'comments'
+    | 'compact'
+    | 'cwd'
+    | 'generatorOpts'
+    | 'include'
+    | 'parserOpts'
+    | 'plugins'
+    | 'retainLines'
+    | 'shouldPrintComment'
+    | 'targets'
+    | 'wrapPluginVisitorMethod'
+  >
 > {
   /**
    * List of presets (a set of plugins) to load and use

packages/babel/src/tsconfig.typetest.json

@@ -0,0 +1,11 @@
+{
+  "extends": "../../../tsconfig.common.json",
+  "compilerOptions": {
+    "paths": {
+      "@babel/core": ["./babelCompat.dummy.ts"]
+    },
+    "skipLibCheck": true
+  },
+  "include": ["./babelCompat.typetest.ts"],
+  "exclude": []
+}

tsconfig.common.json

@@ -12,5 +12,5 @@
     "isolatedModules": true,
     "declaration": true
   },
-  "exclude": ["./examples"]
+  "exclude": ["./examples", "./packages/babel/src/babelCompat.typetest.ts"]
 }

tsconfig.json

@@ -1,4 +1,8 @@
 {
-  "references": [{ "path": "./tsconfig.common.json" }, { "path": "./examples/tsconfig.json" }],
+  "references": [
+    { "path": "./tsconfig.common.json" },
+    { "path": "./examples/tsconfig.json" },
+    { "path": "./packages/babel/src/tsconfig.typetest.json" }
+  ],
   "include": []
 }