refactor(compiler): improve error message for emit skipped (#2518)

src/compiler/language-service.ts

@@ -260,11 +260,10 @@ export const initializeLanguageServiceInstance = (configs: ConfigSet, logger: Lo
       }
       /* istanbul ignore next (this should never happen but is kept for security) */
       if (output.emitSkipped) {
-        const message = interpolate(Errors.CannotProcessFile, { file: fileName })
         if (TS_TSX_REGEX.test(fileName)) {
-          throw new Error(message)
+          throw new Error(interpolate(Errors.CannotProcessFile, { file: fileName }))
         } else {
-          logger.warn(message)
+          logger.warn(interpolate(Errors.CannotProcessFileReturnOriginal, { file: fileName }))
 
           return [code, '{}']
         }

src/utils/messages.ts

@@ -17,7 +17,8 @@ export const enum Errors {
   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.',
   ConfigNoModuleInterop = 'If you have issues related to imports, you should consider setting `esModuleInterop` to `true` in your TypeScript configuration file (usually `tsconfig.json`). See https://blogs.msdn.microsoft.com/typescript/2018/01/31/announcing-typescript-2-7/#easier-ecmascript-module-interoperability for more information.',
   MismatchNodeTargetMapping = 'There is a mismatch between your NodeJs version {{nodeJsVer}} and your TypeScript target {{compilationTarget}}. This might lead to some unexpected errors when running tests with `ts-jest`. To fix this, you can check https://github.com/microsoft/TypeScript/wiki/Node-Target-Mapping',
-  CannotProcessFile = "Unable to process '{{file}}', falling back to original file content. Please make sure that `outDir` in your tsconfig is neither `''` or `'.'`. You can also configure Jest config option `transformIgnorePatterns` to ignore {{file}} from transformation",
+  CannotProcessFileReturnOriginal = "Unable to process '{{file}}', falling back to original file content. You can also configure Jest config option `transformIgnorePatterns` to ignore {{file}} from transformation or make sure that `outDir` in your tsconfig is neither `''` or `'.'`",
+  CannotProcessFile = "Unable to process '{{file}}', please make sure that `outDir` in your tsconfig is neither `''` or `'.'`. You can also configure Jest config option `transformIgnorePatterns` to inform `ts-jest` to transform {{file}}",
 }
 
 /**