jest-reporters: Use global coverage thresholds as high watermarks

CHANGELOG.md

@@ -28,6 +28,7 @@
 - `[jest-get-type]` Add `BigInt` support. ([#8382](https://github.com/facebook/jest/pull/8382))
 - `[jest-matcher-utils]` Add `BigInt` support to `ensureNumbers` `ensureActualIsNumber`, `ensureExpectedIsNumber` ([#8382](https://github.com/facebook/jest/pull/8382))
 - `[jest-reporters]` Export utils for path formatting ([#9162](https://github.com/facebook/jest/pull/9162))
+- `[jest-reporters]` Provides global coverage thresholds as watermarks for istanbul ([#9416](https://github.com/facebook/jest/pull/9416))
 - `[jest-runner]` Warn if a worker had to be force exited ([#8206](https://github.com/facebook/jest/pull/8206))
 - `[jest-runtime]` [**BREAKING**] Do not export `ScriptTransformer` - it can be imported from `@jest/transform` instead ([#9256](https://github.com/facebook/jest/pull/9256))
 - `[jest-runtime]` Use `JestEnvironment.compileFunction` if available to avoid the module wrapper ([#9252](https://github.com/facebook/jest/pull/9252))

packages/jest-reporters/src/__tests__/get_watermarks.test.js

@@ -0,0 +1,43 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+'use strict';
+
+import getWatermarks from '../get_watermarks';
+
+describe('getWatermarks', () => {
+  test(`that watermarks use thresholds as upper target`, () => {
+    const watermarks = getWatermarks({
+      coverageThreshold: {
+        global: {
+          branches: 100,
+          functions: 100,
+          lines: 100,
+          statements: 100,
+        },
+      },
+    });
+
+    expect(watermarks).toEqual({
+      branches: [expect.any(Number), 100],
+      functions: [expect.any(Number), 100],
+      lines: [expect.any(Number), 100],
+      statements: [expect.any(Number), 100],
+    });
+  });
+
+  test(`that watermars are created always created`, () => {
+    const watermarks = getWatermarks({});
+
+    expect(watermarks).toEqual({
+      branches: [expect.any(Number), expect.any(Number)],
+      functions: [expect.any(Number), expect.any(Number)],
+      lines: [expect.any(Number), expect.any(Number)],
+      statements: [expect.any(Number), expect.any(Number)],
+    });
+  });
+});

packages/jest-reporters/src/coverage_reporter.ts

@@ -27,6 +27,7 @@ import {RawSourceMap} from 'source-map';
 import {TransformResult} from '@jest/transform';
 import BaseReporter from './base_reporter';
 import {Context, CoverageReporterOptions, CoverageWorker, Test} from './types';
+import getWatermarks from './get_watermarks';
 
 // This is fixed in a newer versions of source-map, but our dependencies are still stuck on old versions
 interface FixedRawSourceMap extends Omit<RawSourceMap, 'version'> {
@@ -494,6 +495,7 @@ export default class CoverageReporter extends BaseReporter {
         // @ts-ignore
         coverageMap: map,
         dir: this._globalConfig.coverageDirectory,
+        watermarks: getWatermarks(this._globalConfig),
       });
 
       return {map, reportContext};
@@ -506,6 +508,7 @@ export default class CoverageReporter extends BaseReporter {
       dir: this._globalConfig.coverageDirectory,
       // @ts-ignore
       sourceFinder: this._sourceMapStore.sourceFinder,
+      watermarks: getWatermarks(this._globalConfig),
     });
 
     // @ts-ignore

packages/jest-reporters/src/get_watermarks.ts

@@ -0,0 +1,36 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {Config} from '@jest/types';
+import istanbulReport = require('istanbul-lib-report');
+
+export default function getWatermarks(
+  config: Config.GlobalConfig,
+): istanbulReport.Watermarks {
+  const defaultWatermarks = istanbulReport.getDefaultWatermarks();
+
+  const {coverageThreshold} = config;
+
+  if (!coverageThreshold || !coverageThreshold.global) {
+    return defaultWatermarks;
+  }
+
+  const keys: Array<keyof Config.CoverageThresholdValue> = [
+    'branches',
+    'functions',
+    'lines',
+    'statements',
+  ];
+  return keys.reduce((watermarks, key) => {
+    const value = coverageThreshold.global[key];
+    if (value !== undefined) {
+      watermarks[key][1] = value;
+    }
+
+    return watermarks;
+  }, defaultWatermarks);
+}