Support index in it.each with template strings (#10763)

CHANGELOG.md

@@ -53,6 +53,7 @@
 - `[jest-core]` Don't report PerformanceObserver as open handle ([#11123](https://github.com/facebook/jest/pull/11123))
 - `[jest-core]` Use `WeakRef` to hold timers when detecting open handles ([#11277](https://github.com/facebook/jest/pull/11277))
 - `[jest-each]` [**BREAKING**] Ignore excess words in headings ([#8766](https://github.com/facebook/jest/pull/8766))
+- `[jest-each]` Support array index with template strings ([#10763](https://github.com/facebook/jest/pull/10763))
 - `[jest-environment]` [**BREAKING**] Drop support for `runScript` for test environments ([#11155](https://github.com/facebook/jest/pull/11155))
 - `[jest-environment-jsdom]` Use inner realm’s `ArrayBuffer` constructor ([#10885](https://github.com/facebook/jest/pull/10885))
 - `[jest-environment-jsdom]` [**BREAKING**] Remove Node globals `setImmediate` and `clearImmediate` [#11222](https://github.com/facebook/jest/pull/11222)

docs/GlobalAPI.md

@@ -275,7 +275,7 @@ describe.each([
 - `table`: `Tagged Template Literal`
   - First row of variable name column headings separated with `|`
   - One or more subsequent rows of data supplied as template literal expressions using `${value}` syntax.
-- `name`: `String` the title of the test suite, use `$variable` to inject test data into the suite title from the tagged template expressions.
+- `name`: `String` the title of the test suite, use `$variable` to inject test data into the suite title from the tagged template expressions, and `$#` for the index of the row.
   - To inject nested object values use you can supply a keyPath i.e. `$variable.path.to.value`
 - `fn`: `Function` the suite of tests to be ran, this is the function that will receive the test data object.
 - Optionally, you can provide a `timeout` (in milliseconds) for specifying how long to wait for each row before aborting. _Note: The default timeout is 5 seconds._

packages/jest-each/README.md

@@ -338,6 +338,7 @@ each`
 
 - name: `String` the title of the `test`, use `$variable` in the name string to inject test values into the test title from the tagged template expressions
   - To inject nested object values use you can supply a keyPath i.e. `$variable.path.to.value`
+  - You can use `$#` to inject the index of the table row.
 - testFn: `Function` the test logic, this is the function that will receive the parameters of each row as function arguments
 
 #### `each[tagged template].describe(name, suiteFn)`

packages/jest-each/src/__tests__/template.test.ts

@@ -288,17 +288,20 @@ describe('jest-each', () => {
           ${1} | ${1} | ${2}
         `;
         const testFunction = get(eachObject, keyPath);
-        testFunction('expected string: a=$a, b=$b, expected=$expected', noop);
+        testFunction(
+          'expected string: a=$a, b=$b, expected=$expected index=$#',
+          noop,
+        );
 
         const globalMock = get(globalTestMocks, keyPath);
         expect(globalMock).toHaveBeenCalledTimes(2);
         expect(globalMock).toHaveBeenCalledWith(
-          'expected string: a=0, b=1, expected=1',
+          'expected string: a=0, b=1, expected=1 index=0',
           expectFunction,
           undefined,
         );
         expect(globalMock).toHaveBeenCalledWith(
-          'expected string: a=1, b=1, expected=2',
+          'expected string: a=1, b=1, expected=2 index=1',
           expectFunction,
           undefined,
         );
@@ -313,19 +316,19 @@ describe('jest-each', () => {
         `;
         const testFunction = get(eachObject, keyPath);
         testFunction(
-          'add($a, $b) expected string: a=$a, b=$b, expected=$expected',
+          'add($a, $b) expected string: a=$a, b=$b, expected=$expected index=$#',
           noop,
         );
 
         const globalMock = get(globalTestMocks, keyPath);
         expect(globalMock).toHaveBeenCalledTimes(2);
         expect(globalMock).toHaveBeenCalledWith(
-          'add(0, 1) expected string: a=0, b=1, expected=1',
+          'add(0, 1) expected string: a=0, b=1, expected=1 index=0',
           expectFunction,
           undefined,
         );
         expect(globalMock).toHaveBeenCalledWith(
-          'add(1, 1) expected string: a=1, b=1, expected=2',
+          'add(1, 1) expected string: a=1, b=1, expected=2 index=1',
           expectFunction,
           undefined,
         );
@@ -543,17 +546,20 @@ describe('jest-each', () => {
           ${1} | ${1} | ${2}
         `;
         const testFunction = get(eachObject, keyPath);
-        testFunction('expected string: a=$a, b=$b, expected=$expected', noop);
+        testFunction(
+          'expected string: a=$a, b=$b, expected=$expected index=$#',
+          noop,
+        );
 
         const globalMock = get(globalTestMocks, keyPath);
         expect(globalMock).toHaveBeenCalledTimes(2);
         expect(globalMock).toHaveBeenCalledWith(
-          'expected string: a=0, b=1, expected=1',
+          'expected string: a=0, b=1, expected=1 index=0',
           expectFunction,
           undefined,
         );
         expect(globalMock).toHaveBeenCalledWith(
-          'expected string: a=1, b=1, expected=2',
+          'expected string: a=1, b=1, expected=2 index=1',
           expectFunction,
           undefined,
         );

packages/jest-each/src/table/template.ts

@@ -22,9 +22,9 @@ export default (
 ): EachTests => {
   const table = convertRowToTable(row, headings);
   const templates = convertTableToTemplates(table, headings);
-  return templates.map(template => ({
+  return templates.map((template, index) => ({
     arguments: [template],
-    title: interpolate(title, template),
+    title: interpolate(title, template, index),
   }));
 };
 
@@ -47,10 +47,11 @@ const convertTableToTemplates = (
     ),
   );
 
-const interpolate = (title: string, template: Template) =>
+const interpolate = (title: string, template: Template, index: number) =>
   Object.keys(template)
     .reduce(getMatchingKeyPaths(title), []) // aka flatMap
-    .reduce(replaceKeyPathWithValue(template), title);
+    .reduce(replaceKeyPathWithValue(template), title)
+    .replace('$#', '' + index);
 
 const getMatchingKeyPaths = (title: string) => (
   matches: Headings,