[beta] warns the user if jest config transform matches js files without allowJs in tsconfig

src/ts-jest-transformer.spec.ts

@@ -117,7 +117,7 @@ Array [
 
   it('should return stringified version of file', () => {
     config.shouldStringifyContent.mockImplementation(() => true)
-    expect(process()).toMatchInlineSnapshot(`"ts:module.exports=\\"export default \\\\\\"foo\\\\\\"\\""`)
+    expect(process()).toMatchInlineSnapshot(`"module.exports=\\"export default \\\\\\"foo\\\\\\"\\""`)
   })
 
   it('should warn when trying to process js but allowJs is false', () => {
@@ -136,6 +136,28 @@ Array [
 `)
   })
 
+  it('should warn when trying to process unknown file types', () => {
+    args[1] = '/foo/bar.jest'
+    const logs = logTargetMock()
+    logs.clear()
+    expect(process()).toBe(INPUT)
+    expect(logs.lines.warn).toMatchInlineSnapshot(`
+Array [
+  "[level:40] Got a unknown file type to compile (file: /foo/bar.jest). To fix this, in your Jest config change the \`transform\` key which value is \`ts-jest\` so that it does not match this kind of files anymore.
+",
+]
+`)
+    logs.clear()
+    babel = { process: jest.fn(s => `babel:${s}`) }
+    expect(process()).toBe(`babel:${INPUT}`)
+    expect(logs.lines.warn).toMatchInlineSnapshot(`
+Array [
+  "[level:40] Got a unknown file type to compile (file: /foo/bar.jest). To fix this, in your Jest config change the \`transform\` key which value is \`ts-jest\` so that it does not match this kind of files anymore. If you still want Babel to process it, add another entry to the \`transform\` option with value \`babel-jest\` which key matches this type of files.
+",
+]
+`)
+  })
+
   it('should not pass the instrument option to babel-jest', () => {
     babel = { process: jest.fn(s => `babel:${s}`) }
     args[3] = { instrument: true }

src/ts-jest-transformer.ts

@@ -89,30 +89,38 @@ export class TsJestTransformer implements jest.Transformer {
   ): jest.TransformedSource | string {
     this.logger.debug({ fileName: filePath, transformOptions }, 'processing', filePath)
     let result: string | jest.TransformedSource
-    let source: string = input
+    const source: string = input
 
     const configs = this.configsFor(jestConfig)
     const { hooks } = configs
 
     const stringify = configs.shouldStringifyContent(filePath)
     const babelJest = stringify ? undefined : configs.babelJestTransformer
 
-    // handles here what we should simply stringify
-    if (stringify) {
-      source = `module.exports=${JSON.stringify(source)}`
-    }
+    const isDefinitionFile = filePath.endsWith('.d.ts')
+    const isJsFile = !isDefinitionFile && /\.jsx?$/.test(filePath)
+    const isTsFile = isDefinitionFile || /\.tsx?$/.test(filePath)
 
-    // compilation
-    if (filePath.endsWith('.d.ts')) {
+    if (stringify) {
+      // handles here what we should simply stringify
+      result = `module.exports=${JSON.stringify(source)}`
+    } else if (isDefinitionFile) {
       // do not try to compile declaration files
       result = ''
-    } else if (!configs.typescript.options.allowJs && filePath.endsWith('.js')) {
+    } else if (!configs.typescript.options.allowJs && isJsFile) {
       // we've got a '.js' but the compiler option `allowJs` is not set or set to false
       this.logger.warn({ fileName: filePath }, interpolate(Errors.GotJsFileButAllowJsFalse, { path: filePath }))
       result = source
-    } else {
+    } else if (isTsFile) {
       // transpile TS code (source maps are included)
       result = configs.tsCompiler.compile(source, filePath)
+    } else {
+      // we should not get called for files with other extension than js[x], ts[x] and d.ts,
+      // TypeScript will bail if we try to compile, and if it was to call babel, users can
+      // define the transform value with `babel-jest` for this extension instead
+      const message = babelJest ? Errors.GotUnknownFileTypeWithBabel : Errors.GotUnknownFileTypeWithoutBabel
+      this.logger.warn({ fileName: filePath }, interpolate(message, { path: filePath }))
+      result = source
     }
 
     // calling babel-jest transformer

src/util/messages.ts

@@ -13,6 +13,8 @@ export enum Errors {
   MappingOnlyFirstTargetOfPath = 'Mapping only to first target of "{{path}}" because it has more than one ({{count}}).',
   CannotPatchBabelCore6 = 'Error while trying to patch babel-core/lib/transformation/file: {{error}}',
   GotJsFileButAllowJsFalse = 'Got a `.js` file to compile while `allowJs` option is not set to `true` (file: {{path}}). To fix this:\n  - if you want TypeScript to process JS files, set `allowJs` to `true` in your TypeScript config (usually tsconfig.json)\n  - if you do not want TypeScript to process your `.js` files, in your Jest config change the `transform` key which value is `ts-jest` so that it does not match `.js` files anymore',
+  GotUnknownFileTypeWithoutBabel = 'Got a unknown file type to compile (file: {{path}}). To fix this, in your Jest config change the `transform` key which value is `ts-jest` so that it does not match this kind of files anymore.',
+  GotUnknownFileTypeWithBabel = 'Got a unknown file type to compile (file: {{path}}). To fix this, in your Jest config change the `transform` key which value is `ts-jest` so that it does not match this kind of files anymore. If you still want Babel to process it, add another entry to the `transform` option with value `babel-jest` which key matches this type of files.',
 }
 
 export enum Helps {

tsconfig.build.json

@@ -4,7 +4,7 @@
     "sourceMap": false,
     "inlineSources": false,
     "inlineSourceMap": false,
-    "removeComments": true,
+    "noEmit": false,
     "outDir": "dist",
     "rootDir": "src",
   },

tsconfig.json

@@ -1,6 +1,7 @@
 {
   "compilerOptions": {
-    "declaration": true,
+    "declaration": false,
+    "noEmit": true,
     "downlevelIteration": true,
     "esModuleInterop": true,
     "experimentalDecorators": true,
@@ -18,7 +19,7 @@
     "noImplicitReturns": true,
     "noUnusedLocals": true,
     "noUnusedParameters": true,
-    "removeComments": false,
+    "removeComments": true,
     "resolveJsonModule": true,
     "skipLibCheck": true,
     "sourceMap": false,