Add One Double Zero as coverage provider

docs/CLI.md

@@ -170,7 +170,7 @@ The directory where Jest should output its coverage files.
 
 ### `--coverageProvider=<provider>`
 
-Indicates which provider should be used to instrument code for coverage. Allowed values are `babel` (default) or `v8`.
+Indicates which provider should be used to instrument code for coverage. Allowed values are `babel` (default), `v8` or `odz`.
 
 ### `--debug`
 

docs/Configuration.md

@@ -224,11 +224,35 @@ Default: `false`
 
 Indicates whether the coverage information should be collected while executing the test. Because this retrofits all executed files with coverage collection statements, it may significantly slow down your tests.
 
-Jest ships with two coverage providers: `babel` (default) and `v8`. See the [`coverageProvider`](#coverageprovider-string) option for more details.
+Jest ships with three coverage providers: `babel` (default), `v8` and `odz`. See the [`coverageProvider`](#coverageprovider-string) option for more details.
 
 :::info
 
-The `babel` and `v8` coverage providers use `/* istanbul ignore next */` and `/* c8 ignore next */` comments to exclude lines from coverage reports, respectively. For more information, you can view the [`istanbuljs` documentation](https://github.com/istanbuljs/nyc#parsing-hints-ignoring-lines) and the [`c8` documentation](https://github.com/bcoe/c8#ignoring-uncovered-lines-functions-and-blocks).
+The `babel` and `v8` coverage providers use `/* istanbul ignore next */` and `/* c8 ignore next */` comments to exclude lines from coverage reports, respectively. For more information, you can view the [`istanbuljs` documentation](https://github.com/istanbuljs/nyc#parsing-hints-ignoring-lines) and the [`c8` documentation](https://github.com/bcoe/c8#ignoring-uncovered-lines-functions-and-blocks). The `odz` coverage provider doesn't support exclusion comment.
+
+The `v8` coverage provider comes with the following tradeoffs:
+
+- It is not a 1:1 replacement for Babel/Istanbul coverage
+
+  - Switching between the two will usually change the reported coverage statistics, which can change whether coverage thresholds are reached or not
+  - Switching between the two can cause regions of uncovered code to be discovered or ignored (This is mostly just an overall summary of the other points)
+
+- It works by taking a coverage report for output/transpiled code, and then using `v8-to-istanbul` and source maps to convert that report into an Istanbul-compatible format
+  - This is an inherently imprecise and heuristic-driven process, though in many cases it works well enough for practical purposes
+  - In some cases this can give confusing or misleading results, or fail to distinguish between user code and generated code (e.g. uncovered branches introduced by `__esModule` detection shims)
+  - Babel/Istanbul is able to be more precise because it usually operates directly on the user's original source code
+- It tracks “blocks”, not individual statements
+  - In particular, if you have a sequence of statements, and the middle statements always throw an exception, V8 coverage will mark the later statements as “covered” even though they never ran
+  - This is a deliberate tradeoff made by the V8 developers who implemented coverage
+  - Babel/Istanbul is able to be more precise because it explicitly instruments every source statement
+- It does not track the else branch of an if-statement without an explicit else
+
+  - So if a one-sided if-statement's condition is always true, V8 will not warn about an uncovered branch
+  - Babel/Istanbul is able to track these by artificially inserting an else with a branch counter
+
+- It does not respect the `collectCoverageFrom` Jest configuration: regardless of the value of `collectCoverageFrom`, it emits coverage report for whatever file that was encountered during the execution of the tests.
+
+The `odz` coverage provider also makes use of V8 coverage data, but doesn't come any of the `v8` provider tradeoffs because it operates at the AST level.
 
 :::
 
@@ -314,7 +338,7 @@ These pattern strings match against the full path. Use the `<rootDir>` string to
 
 ### `coverageProvider` \[string]
 
-Indicates which provider should be used to instrument code for coverage. Allowed values are `babel` (default) or `v8`.
+Indicates which provider should be used to instrument code for coverage. Allowed values are `babel` (default), `v8` and `odz`.
 
 ### `coverageReporters` \[array&lt;string | \[string, options]&gt;]
 

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

@@ -0,0 +1,116 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`prints correct coverage report, if a CJS module is put under test without transformation 1`] = `
+"  console.log
+    this will print
+
+      at covered (module.js:11:11)
+
+--------------|---------|----------|---------|---------|-------------------
+File          | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
+--------------|---------|----------|---------|---------|-------------------
+All files     |      60 |       50 |      50 |      60 |                   
+ module.js    |   66.66 |       50 |      50 |   66.66 | 14-15,19          
+ uncovered.js |       0 |      100 |     100 |       0 | 8                 
+--------------|---------|----------|---------|---------|-------------------"
+`;
+
+exports[`prints correct coverage report, if a TS module is transpiled by Babel to CJS and put under test 1`] = `
+"  console.log
+    this will print
+
+      at log (module.ts:13:11)
+
+--------------|---------|----------|---------|---------|-------------------
+File          | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
+--------------|---------|----------|---------|---------|-------------------
+All files     |    62.5 |       50 |      50 |    62.5 |                   
+ module.ts    |    62.5 |       50 |      50 |    62.5 | 16-17,21          
+ types.ts     |       0 |        0 |       0 |       0 |                   
+ uncovered.ts |       0 |        0 |       0 |       0 |                   
+--------------|---------|----------|---------|---------|-------------------"
+`;
+
+exports[`prints correct coverage report, if a TS module is transpiled by custom transformer to ESM put under test 1`] = `
+"  console.log
+    this will print
+
+      at covered (module.ts:13:11)
+
+--------------|---------|----------|---------|---------|-------------------
+File          | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
+--------------|---------|----------|---------|---------|-------------------
+All files     |    62.5 |       50 |      50 |    62.5 |                   
+ module.ts    |    62.5 |       50 |      50 |    62.5 | 16-17,21          
+ types.ts     |       0 |        0 |       0 |       0 |                   
+ uncovered.ts |       0 |        0 |       0 |       0 |                   
+--------------|---------|----------|---------|---------|-------------------"
+`;
+
+exports[`prints correct coverage report, if an ESM module is put under test without transformation 1`] = `
+"  console.log
+    this will print
+
+      at covered (module.js:11:11)
+
+--------------|---------|----------|---------|---------|-------------------
+File          | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
+--------------|---------|----------|---------|---------|-------------------
+All files     |    62.5 |       50 |      50 |    62.5 |                   
+ module.js    |    62.5 |       50 |      50 |    62.5 | 14-15,19          
+ uncovered.js |       0 |        0 |       0 |       0 |                   
+--------------|---------|----------|---------|---------|-------------------"
+`;
+
+exports[`prints coverage with empty sourcemaps 1`] = `
+"----------|---------|----------|---------|---------|-------------------
+File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
+----------|---------|----------|---------|---------|-------------------
+All files |       0 |        0 |       0 |       0 |                   
+ types.ts |       0 |        0 |       0 |       0 |                   
+----------|---------|----------|---------|---------|-------------------"
+`;
+
+exports[`prints coverage with missing sourcemaps 1`] = `
+"  console.log
+    42
+
+      at Object.log (__tests__/Thing.test.js:10:9)
+
+----------|---------|----------|---------|---------|-------------------
+File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
+----------|---------|----------|---------|---------|-------------------
+All files |     100 |      100 |     100 |     100 |                   
+ Thing.js |     100 |      100 |     100 |     100 |                   
+ x.css    |       0 |        0 |       0 |       0 |                   
+----------|---------|----------|---------|---------|-------------------"
+`;
+
+exports[`reports coverage with \`resetModules\` 1`] = `
+"  console.log
+    this will print
+
+      at log (module.js:11:11)
+
+  console.log
+    this will print
+
+      at log (module.js:11:11)
+
+--------------|---------|----------|---------|---------|-------------------
+File          | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
+--------------|---------|----------|---------|---------|-------------------
+All files     |      60 |       50 |      50 |      60 |                   
+ module.js    |   66.66 |       50 |      50 |   66.66 | 14-15,19          
+ uncovered.js |       0 |      100 |     100 |       0 | 8                 
+--------------|---------|----------|---------|---------|-------------------"
+`;
+
+exports[`vm script coverage generator 1`] = `
+"-------------|---------|----------|---------|---------|-------------------
+File         | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
+-------------|---------|----------|---------|---------|-------------------
+All files    |      80 |       75 |   66.66 |      80 |                   
+ vmscript.js |      80 |       75 |   66.66 |      80 | 20-21             
+-------------|---------|----------|---------|---------|-------------------"
+`;

e2e/__tests__/coverageProviderODZ.test.ts

@@ -0,0 +1,120 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import * as path from 'path';
+import runJest from '../runJest';
+
+const DIR = path.resolve(__dirname, '../coverage-provider-v8');
+
+test('prints coverage with missing sourcemaps', () => {
+  const sourcemapDir = path.join(DIR, 'no-sourcemap');
+
+  const {stdout, exitCode} = runJest(
+    sourcemapDir,
+    ['--coverage', '--coverage-provider', 'odz'],
+    {stripAnsi: true},
+  );
+
+  expect(exitCode).toBe(0);
+  expect(stdout).toMatchSnapshot();
+});
+
+test('prints coverage with empty sourcemaps', () => {
+  const sourcemapDir = path.join(DIR, 'empty-sourcemap');
+
+  const {stdout, exitCode} = runJest(
+    sourcemapDir,
+    ['--coverage', '--coverage-provider', 'odz'],
+    {stripAnsi: true},
+  );
+
+  expect(exitCode).toBe(0);
+  expect(stdout).toMatchSnapshot();
+});
+
+test('reports coverage with `resetModules`', () => {
+  const sourcemapDir = path.join(DIR, 'with-resetModules');
+
+  const {stdout, exitCode} = runJest(
+    sourcemapDir,
+    ['--coverage', '--coverage-provider', 'odz'],
+    {stripAnsi: true},
+  );
+
+  expect(exitCode).toBe(0);
+  expect(stdout).toMatchSnapshot();
+});
+
+test('prints correct coverage report, if a CJS module is put under test without transformation', () => {
+  const sourcemapDir = path.join(DIR, 'cjs-native-without-sourcemap');
+
+  const {stdout, exitCode} = runJest(
+    sourcemapDir,
+    ['--coverage', '--coverage-provider', 'odz', '--no-cache'],
+    {stripAnsi: true},
+  );
+
+  expect(exitCode).toBe(0);
+  expect(stdout).toMatchSnapshot();
+});
+
+test('prints correct coverage report, if a TS module is transpiled by Babel to CJS and put under test', () => {
+  const sourcemapDir = path.join(DIR, 'cjs-with-babel-transformer');
+
+  const {stdout, exitCode} = runJest(
+    sourcemapDir,
+    ['--coverage', '--coverage-provider', 'odz', '--no-cache'],
+    {stripAnsi: true},
+  );
+
+  expect(exitCode).toBe(0);
+  expect(stdout).toMatchSnapshot();
+});
+
+test('prints correct coverage report, if an ESM module is put under test without transformation', () => {
+  const sourcemapDir = path.join(DIR, 'esm-native-without-sourcemap');
+
+  const {stdout, exitCode} = runJest(
+    sourcemapDir,
+    ['--coverage', '--coverage-provider', 'odz', '--no-cache'],
+    {
+      nodeOptions: '--experimental-vm-modules --no-warnings',
+      stripAnsi: true,
+    },
+  );
+
+  expect(exitCode).toBe(0);
+  expect(stdout).toMatchSnapshot();
+});
+
+test('prints correct coverage report, if a TS module is transpiled by custom transformer to ESM put under test', () => {
+  const sourcemapDir = path.join(DIR, 'esm-with-custom-transformer');
+
+  const {stdout, exitCode} = runJest(
+    sourcemapDir,
+    ['--coverage', '--coverage-provider', 'odz', '--no-cache'],
+    {
+      nodeOptions: '--experimental-vm-modules --no-warnings',
+      stripAnsi: true,
+    },
+  );
+
+  expect(exitCode).toBe(0);
+  expect(stdout).toMatchSnapshot();
+});
+
+test('vm script coverage generator', () => {
+  const dir = path.resolve(__dirname, '../vmscript-coverage');
+  const {stdout, exitCode} = runJest(
+    dir,
+    ['--coverage', '--coverage-provider', 'odz'],
+    {stripAnsi: true},
+  );
+
+  expect(exitCode).toBe(0);
+  expect(stdout).toMatchSnapshot();
+});

e2e/coverage-provider-v8/empty-sourcemap/package.json

@@ -2,6 +2,9 @@
   "name": "empty-sourcemap",
   "version": "1.0.0",
   "jest": {
-    "testEnvironment": "node"
+    "testEnvironment": "node",
+    "collectCoverageFrom": [
+      "<rootDir>/types.ts"
+    ]
   }
 }

e2e/coverage-provider-v8/no-sourcemap/package.json

@@ -6,6 +6,14 @@
     "transform": {
       "\\.[jt]sx?$": "babel-jest",
       "\\.css$": "<rootDir>/cssTransform.js"
-    }
+    },
+    "moduleFileExtensions": [
+      "js",
+      "css"
+    ],
+    "collectCoverageFrom": [
+      "<rootDir>/Thing.js",
+      "<rootDir>/x.css"
+    ]
   }
 }

package.json

@@ -202,7 +202,8 @@
     "jest": "workspace:*",
     "jest-environment-node": "workspace:*",
     "psl": "patch:psl@npm:^1.9.0#./.yarn/patches/psl-npm-1.9.0-a546edad1a.patch",
-    "ts-node@^10.5.0": "patch:ts-node@npm:^10.5.0#./.yarn/patches/ts-node-npm-10.9.1-6c268be7f4.patch"
+    "ts-node@^10.5.0": "patch:ts-node@npm:^10.5.0#./.yarn/patches/ts-node-npm-10.9.1-6c268be7f4.patch",
+    "typescript": "~5.5.4"
   },
   "packageManager": "[email protected]"
 }

packages/jest-cli/src/args.ts

@@ -213,8 +213,9 @@ export const options: {[key: string]: Options} = {
     type: 'array',
   },
   coverageProvider: {
-    choices: ['babel', 'v8'],
-    description: 'Select between Babel and V8 to collect coverage',
+    choices: ['babel', 'v8', 'odz'],
+    description:
+      'Select between Babel, V8 and One Double Zero to collect coverage',
     requiresArg: true,
   },
   coverageReporters: {

packages/jest-reporters/package.json

@@ -34,6 +34,7 @@
     "jest-message-util": "workspace:*",
     "jest-util": "workspace:*",
     "jest-worker": "workspace:*",
+    "one-double-zero": "1.0.0-beta.14",
     "slash": "^3.0.0",
     "string-length": "^4.0.1",
     "strip-ansi": "^6.0.0",