feat(options): Allow customSnapshotIdentifier to be a function (ameri…

…canexpress#140)

Related americanexpress#62

README.md

@@ -43,7 +43,7 @@ See [the examples](./examples/README.md) for more detailed usage or read about a
   * Please note the `threshold` set in the `customDiffConfig` is the per pixel sensitivity threshold. For example with a source pixel colour of `#ffffff` (white) and a comparison pixel colour of `#fcfcfc` (really light grey) if you set the threshold to 0 then it would trigger a failure *on that pixel*. However if you were to use say 0.5 then it wouldn't, the colour difference would need to be much more extreme to trigger a failure on that pixel, say `#000000` (black)
 * `customSnapshotsDir`: A custom absolute path of a directory to keep this snapshot in
 * `customDiffDir`: A custom absolute path of a directory to keep this diff in
-* `customSnapshotIdentifier`: A custom name to give this snapshot. If not provided one is computed automatically
+* `customSnapshotIdentifier`: A custom name to give this snapshot. If not provided one is computed automatically. When a function is provided it is called with an object containing `testPath`, `currentTestName`, `counter` and `defaultIdentifier` as its first argument. The function must return an identifier to use for the snapshot.
 * `diffDirection`: (default: `horizontal`) (options `horizontal` or `vertical`) Changes diff image layout direction
 * `noColors`: (default `false`) Removes colouring from console output, useful if storing the results in a file
 * `failureThreshold`: (default `0`) Sets the threshold that would trigger a test failure based on the `failureThresholdType` selected. This is different to the `customDiffConfig.threshold` above, that is the per pixel failure threshold, this is the failure threshold for the entire comparison.

__tests__/__snapshots__/index.spec.js.snap

@@ -28,3 +28,5 @@ See diff for details: path/to/result.png"
 `;
 
 exports[`toMatchImageSnapshot when retryTimes is set should throw an error when called without customSnapshotIdentifier 2`] = `"A unique customSnapshotIdentifier must be set when jest.retryTimes() is used"`;
+
+exports[`toMatchImageSnapshot when retryTimes is set should throw an error when called without customSnapshotIdentifier 4`] = `"A unique customSnapshotIdentifier must be set when jest.retryTimes() is used"`;

__tests__/index.spec.js

@@ -224,6 +224,22 @@ describe('toMatchImageSnapshot', () => {
     const { runDiffImageToSnapshot } = require('../src/diff-snapshot');
 
     expect(runDiffImageToSnapshot.mock.calls[0][0].snapshotIdentifier).toBe('custom-name');
+
+    matcherAtTest('pretendthisisanimagebuffer', { customSnapshotIdentifier: () => 'functional-name' });
+    expect(runDiffImageToSnapshot.mock.calls[1][0].snapshotIdentifier).toBe('functional-name');
+
+    matcherAtTest('pretendthisisanimagebuffer', { customSnapshotIdentifier: () => '' });
+    expect(runDiffImageToSnapshot.mock.calls[2][0].snapshotIdentifier).toBe('test-spec-js-test-3');
+
+    const mockCustomSnap = jest.fn();
+    matcherAtTest('pretendthisisanimagebuffer', { customSnapshotIdentifier: mockCustomSnap });
+
+    expect(mockCustomSnap).toHaveBeenCalledWith({
+      testPath: mockTestContext.testPath,
+      currentTestName: mockTestContext.currentTestName,
+      counter: 4,
+      defaultIdentifier: 'test-spec-js-test-4',
+    });
   });
 
   it('attempts to update snapshots if snapshotState has updateSnapshot flag set', () => {
@@ -445,6 +461,9 @@ describe('toMatchImageSnapshot', () => {
 
       expect(() => expect('pretendthisisanimagebuffer').toMatchImageSnapshot())
         .toThrowErrorMatchingSnapshot();
+
+      expect(() => expect('pretendthisisanimagebuffer').toMatchImageSnapshot({ customSnapshotIdentifier: () => '' }))
+        .toThrowErrorMatchingSnapshot();
     });
 
     it('should only increment unmatched when test fails in excess of retryTimes', () => {

src/index.js

@@ -90,12 +90,29 @@ function createSnapshotIdentifier({
   customSnapshotIdentifier,
   snapshotState,
 }) {
-  const snapshotIdentifier = customSnapshotIdentifier || kebabCase(`${path.basename(testPath)}-${currentTestName}-${snapshotState._counters.get(currentTestName)}`);
+  const counter = snapshotState._counters.get(currentTestName);
+  const defaultIdentifier = kebabCase(`${path.basename(testPath)}-${currentTestName}-${counter}`);
+
+  let snapshotIdentifier = customSnapshotIdentifier || defaultIdentifier;
+
+  if (typeof customSnapshotIdentifier === 'function') {
+    const customRes = customSnapshotIdentifier({
+      testPath, currentTestName, counter, defaultIdentifier,
+    });
+
+    if (retryTimes && !customRes) {
+      throw new Error('A unique customSnapshotIdentifier must be set when jest.retryTimes() is used');
+    }
+
+    snapshotIdentifier = customRes || defaultIdentifier;
+  }
+
   if (retryTimes) {
     if (!customSnapshotIdentifier) throw new Error('A unique customSnapshotIdentifier must be set when jest.retryTimes() is used');
 
     timesCalled.set(snapshotIdentifier, (timesCalled.get(snapshotIdentifier) || 0) + 1);
   }
+
   return snapshotIdentifier;
 }