Support custom inline snapshot matchers

e2e/__tests__/__snapshots__/toMatchInlineSnapshot.test.ts.snap

@@ -160,6 +160,23 @@ test('inline snapshots', async () => {
 
 `;
 
+exports[`supports custom matchers: custom matchers 1`] = `
+const {toMatchInlineSnapshot} = require('jest-snapshot');
+expect.extend({
+  toMatchCustomInlineSnapshot(received, ...args) {
+    return toMatchInlineSnapshot.call(this, received, ...args);
+  },
+});
+test('inline snapshots', () => {
+  expect({apple: 'original value'}).toMatchCustomInlineSnapshot(\`
+    Object {
+      "apple": "original value",
+    }
+  \`);
+});
+
+`;
+
 exports[`writes snapshots with non-literals in expect(...) 1`] = `
 it('works with inline snapshots', () => {
   expect({a: 1}).toMatchInlineSnapshot(\`

e2e/__tests__/toMatchInlineSnapshot.test.ts

@@ -266,3 +266,25 @@ test('handles mocking native modules prettier relies on', () => {
   expect(stderr).toMatch('1 snapshot written from 1 test suite.');
   expect(exitCode).toBe(0);
 });
+
+test('supports custom matchers', () => {
+  const filename = 'custom-matchers.test.js';
+  const test = `
+    const { toMatchInlineSnapshot } = require('jest-snapshot');
+    expect.extend({
+      toMatchCustomInlineSnapshot(received, ...args) {
+        return toMatchInlineSnapshot.call(this, received, ...args);
+      }
+    });
+    test('inline snapshots', () => {
+      expect({apple: "original value"}).toMatchCustomInlineSnapshot();
+    });
+  `;
+
+  writeFiles(TESTS_DIR, {[filename]: test});
+  const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false', filename]);
+  const fileAfter = readFile(filename);
+  expect(stderr).toMatch('1 snapshot written from 1 test suite.');
+  expect(exitCode).toBe(0);
+  expect(wrap(fileAfter)).toMatchSnapshot('custom matchers');
+});

packages/expect/src/index.ts

@@ -297,7 +297,7 @@ const makeThrowingMatcher = (
       }
     };
 
-    const handlError = (error: Error) => {
+    const handleError = (error: Error) => {
       if (
         matcher[INTERNAL_MATCHER_FLAG] === true &&
         !(error instanceof JestAssertionError) &&
@@ -314,7 +314,15 @@ const makeThrowingMatcher = (
     let potentialResult: ExpectationResult;
 
     try {
-      potentialResult = matcher.call(matcherContext, actual, ...args);
+      potentialResult =
+        matcher[INTERNAL_MATCHER_FLAG] === true
+          ? matcher.call(matcherContext, actual, ...args)
+          : // It's a trap specifically for inline snapshot to capture this name
+            // in the stack trace, so that it can correctly get the custom matcher
+            // function call.
+            (function __EXTERNAL_MATCHER_TRAP__() {
+              return matcher.call(matcherContext, actual, ...args);
+            })();
 
       if (isPromise(potentialResult)) {
         const asyncResult = potentialResult as AsyncExpectationResult;
@@ -325,14 +333,14 @@ const makeThrowingMatcher = (
 
         return asyncResult
           .then(aResult => processResult(aResult, asyncError))
-          .catch(error => handlError(error));
+          .catch(error => handleError(error));
       } else {
         const syncResult = potentialResult as SyncExpectationResult;
 
         return processResult(syncResult);
       }
     } catch (error) {
-      return handlError(error);
+      return handleError(error);
     }
   };
 

packages/jest-snapshot/src/State.ts

@@ -14,6 +14,7 @@ import {
   getSnapshotData,
   keyToTestName,
   removeExtraLineBreaks,
+  removeLinesBeforeExternalMatcherTrap,
   saveSnapshotFile,
   serialize,
   testNameToKey,
@@ -104,7 +105,9 @@ export default class SnapshotState {
     this._dirty = true;
     if (options.isInline) {
       const error = options.error || new Error();
-      const lines = getStackTraceLines(error.stack || '');
+      const lines = getStackTraceLines(
+        removeLinesBeforeExternalMatcherTrap(error.stack || ''),
+      );
       const frame = getTopFrame(lines);
       if (!frame) {
         throw new Error(

packages/jest-snapshot/src/inline_snapshots.ts

@@ -78,21 +78,34 @@ const saveSnapshotsForFile = (
     ? prettier.getFileInfo.sync(sourceFilePath).inferredParser
     : (config && config.parser) || simpleDetectParser(sourceFilePath);
 
+  // Record the matcher names seen in insertion parser and pass them down one
+  // by one to formatting parser.
+  const snapshotMatcherNames: Array<string> = [];
+
   // Insert snapshots using the custom parser API. After insertion, the code is
   // formatted, except snapshot indentation. Snapshots cannot be formatted until
   // after the initial format because we don't know where the call expression
   // will be placed (specifically its indentation).
   const newSourceFile = prettier.format(sourceFile, {
     ...config,
     filepath: sourceFilePath,
-    parser: createInsertionParser(snapshots, inferredParser, babelTraverse),
+    parser: createInsertionParser(
+      snapshots,
+      snapshotMatcherNames,
+      inferredParser,
+      babelTraverse,
+    ),
   });
 
   // Format the snapshots using the custom parser API.
   const formattedNewSourceFile = prettier.format(newSourceFile, {
     ...config,
     filepath: sourceFilePath,
-    parser: createFormattingParser(inferredParser, babelTraverse),
+    parser: createFormattingParser(
+      snapshotMatcherNames,
+      inferredParser,
+      babelTraverse,
+    ),
   });
 
   if (formattedNewSourceFile !== sourceFile) {
@@ -166,6 +179,7 @@ const getAst = (
 // This parser inserts snapshots into the AST.
 const createInsertionParser = (
   snapshots: Array<InlineSnapshot>,
+  snapshotMatcherNames: Array<string>,
   inferredParser: string,
   babelTraverse: Function,
 ) => (
@@ -198,6 +212,9 @@ const createInsertionParser = (
           'Jest: Multiple inline snapshots for the same call are not supported.',
         );
       }
+
+      snapshotMatcherNames.push(callee.property.name);
+
       const snapshotIndex = args.findIndex(
         ({type}) => type === 'TemplateLiteral',
       );
@@ -228,6 +245,7 @@ const createInsertionParser = (
 
 // This parser formats snapshots to the correct indentation.
 const createFormattingParser = (
+  snapshotMatcherNames: Array<string>,
   inferredParser: string,
   babelTraverse: Function,
 ) => (
@@ -244,7 +262,7 @@ const createFormattingParser = (
       if (
         callee.type !== 'MemberExpression' ||
         callee.property.type !== 'Identifier' ||
-        callee.property.name !== 'toMatchInlineSnapshot' ||
+        callee.property.name !== snapshotMatcherNames[0] ||
         !callee.loc ||
         callee.computed
       ) {
@@ -264,6 +282,8 @@ const createFormattingParser = (
         return;
       }
 
+      snapshotMatcherNames.shift();
+
       const useSpaces = !options.useTabs;
       snapshot = indent(
         snapshot,

packages/jest-snapshot/src/utils.ts

@@ -136,6 +136,21 @@ export const removeExtraLineBreaks = (string: string): string =>
     ? string.slice(1, -1)
     : string;
 
+export const removeLinesBeforeExternalMatcherTrap = (stack: string): string => {
+  const lines = stack.split('\n');
+
+  for (let i = 0; i < lines.length; i += 1) {
+    // It's a function name specified in `packages/expect/src/index.ts`
+    // for external custom matchers.
+    if (lines[i].includes('__EXTERNAL_MATCHER_TRAP__')) {
+      lines.splice(1, i);
+      break;
+    }
+  }
+
+  return lines.join('\n');
+};
+
 const escapeRegex = true;
 const printFunctionName = false;