include error message for preset json

CHANGELOG.md

@@ -16,6 +16,7 @@
 * `[jest-resolve]` changes method of determining builtin modules to include missing builtins ([#4740](https://github.com/facebook/jest/pull/4740))
 * `[pretty-format]` Prevent error in pretty-format for window in jsdom test env ([#4750](https://github.com/facebook/jest/pull/4750))
 * `[jest-resolve]` Preserve module identity for symlinks ([#4761](https://github.com/facebook/jest/pull/4761))
+* `[jest-config]` Include error message for `preset` json ([#4766](https://github.com/facebook/jest/pull/4766))
 
 ### Features
 * `[jest-environment-*]` [**BREAKING**] Add Async Test Environment APIs, dispose is now teardown ([#4506](https://github.com/facebook/jest/pull/4506))

packages/jest-config/src/__tests__/__snapshots__/normalize.test.js.snap

@@ -17,6 +17,17 @@ exports[`Upgrade help logs a warning when \`scriptPreprocessor\` and/or \`prepro
 <yellow></>"
 `;
 
+exports[`preset throws when preset is invalid 1`] = `
+"<red><bold><bold>● <bold>Validation Error</>:</>
+<red></>
+<red>  Preset <bold>react-native</> is invalid:</>
+<red>  Unexpected token } in JSON at position 104</>
+<red></>
+<red>  <bold>Configuration Documentation:</></>
+<red>  https://facebook.github.io/jest/docs/configuration.html</>
+<red></>"
+`;
+
 exports[`preset throws when preset not found 1`] = `
 "<red><bold><bold>● <bold>Validation Error</>:</>
 <red></>

packages/jest-config/src/__tests__/jest-preset.json

@@ -0,0 +1,7 @@
+{
+  "moduleNameMapper": {
+    "b": "b"
+  },
+  "modulePathIgnorePatterns": ["b"],
+  "setupFiles": ["b"],
+}

packages/jest-config/src/__tests__/normalize.test.js

@@ -877,6 +877,22 @@ describe('preset', () => {
     }).toThrowErrorMatchingSnapshot();
   });
 
+  test('throws when preset is invalid', () => {
+    jest.mock('/node_modules/react-native/jest-preset.json', () =>
+      require.requireActual('./jest-preset.json'),
+    );
+
+    expect(() => {
+      normalize(
+        {
+          preset: 'react-native',
+          rootDir: '/root/path/foo',
+        },
+        {},
+      );
+    }).toThrowErrorMatchingSnapshot();
+  });
+
   test('works with "react-native"', () => {
     expect(() => {
       normalize(

packages/jest-config/src/normalize.js

@@ -64,6 +64,11 @@ const setupPreset = (
     // $FlowFixMe
     preset = (require(presetModule): InitialOptions);
   } catch (error) {
+    if (error instanceof SyntaxError) {
+      throw createConfigError(
+        `  Preset ${chalk.bold(presetPath)} is invalid:\n  ${error.message}`,
+      );
+    }
     throw createConfigError(`  Preset ${chalk.bold(presetPath)} not found.`);
   }