fix: handling the file placeholder when merging (#362)

Author: bahmutov

Diff for: .circleci/config.yml

@@ -393,6 +393,40 @@ workflows:
                   ../../node_modules/.bin/only-covered --from coverage/coverage-final.json main.js second.js not-covered.js
                 working_directory: examples/all-files
 
+      - cypress/run:
+          attach-workspace: true
+          name: example-placeholders
+          requires:
+            - cypress/install
+          # there are no jobs to follow this one
+          # so no need to save the workspace files (saves time)
+          no-workspace: true
+          command: npx cypress run --project examples/placeholders
+          # store screenshots and videos
+          store_artifacts: true
+          post-steps:
+            - run: cat examples/placeholders/.nyc_output/out.json
+            - run: cat examples/placeholders/coverage/coverage-final.json
+            # store the created coverage report folder
+            # you can click on it in the CircleCI UI
+            # to see live static HTML site
+            - store_artifacts:
+                path: examples/placeholders/coverage
+            # make sure the examples captures 100% of code
+            - run:
+                command: npx nyc report --check-coverage true --lines 100
+                working_directory: examples/placeholders
+            - run:
+                name: Check code coverage 📈
+                # we will check the final coverage report
+                # to make sure it only has files we are interested in
+                # because there are files covered at 0 in the report
+                command: |
+                  ../../node_modules/.bin/check-coverage src/a.js
+                  ../../node_modules/.bin/check-coverage src/a.js
+                  ../../node_modules/.bin/only-covered --from coverage/coverage-final.json src/a.js src/b.js
+                working_directory: examples/placeholders
+
       - cypress/run:
           attach-workspace: true
           name: example-exclude-files
@@ -544,4 +578,5 @@ workflows:
             - example-docker-paths
             - example-use-webpack
             - example-all-files
+            - example-placeholders
             - Windows test

Diff for: README.md

@@ -21,9 +21,9 @@ Register tasks in your `cypress/plugins/index.js` file
 ```js
 module.exports = (on, config) => {
   require('@cypress/code-coverage/task')(on, config)
-  
+
   // add other tasks to be registered here
-  
+
   // IMPORTANT to return the config object
   // with the any changed environment variables
   return config
@@ -189,7 +189,7 @@ For any other server, define the endpoint yourself and return the coverage objec
 ```js
 if (global.__coverage__) {
   // add method "GET /__coverage__" and response with JSON
-  onRequest = response => response.sendJSON({ coverage: global.__coverage__ })
+  onRequest = (response) => response.sendJSON({ coverage: global.__coverage__ })
 }
 ```
 
@@ -365,6 +365,7 @@ Full examples we use for testing in this repository:
 ### External examples
 
 Look up the list of examples under GitHub topic [cypress-code-coverage-example](https://github.com/topics/cypress-code-coverage-example)
+
 - [cypress-io/cypress-realworld-app](https://github.com/cypress-io/cypress-realworld-app) is an easy to setup and run real-world application with E2E, API, and unit tests that achieves 100% code-coverage for both front and back end code. Its CI pipeline also reports code-coverage reports across parallelized test runs to [Codecov](https://codecov.io/gh/cypress-io/cypress-realworld-app).
 - [cypress-io/cypress-example-todomvc-redux](https://github.com/cypress-io/cypress-example-todomvc-redux) is a React / Redux application with 100% code coverage.
 - [cypress-io/cypress-example-conduit-app](https://github.com/cypress-io/cypress-example-conduit-app) shows how to collect the coverage information from both back and front end code and merge it into a single report. The E2E test step runs in parallel in several CI containers, each saving just partial test coverage information. Then a merge job runs taking artifacts and combining coverage into the final report to be sent to an exteral coverage as a service app.
@@ -427,6 +428,14 @@ $ DEBUG=code-coverage npm run dev
   code-coverage saving coverage report using command: "nyc report --report-dir ./coverage --reporter=lcov --reporter=clover --reporter=json" +3ms
 ```
 
+Deeply nested object will sometimes have `[object Object]` values printed. You can print these nested objects by specifying a deeper depth by adding `DEBUG_DEPTH=` setting
+
+```shell
+$ DEBUG_DEPTH=10 DEBUG=code-coverage npm run dev
+```
+
+### Common issues
+
 Common issue: [not instrumenting your application when running Cypress](#instrument-your-application).
 
 If the plugin worked before in version X, but stopped after upgrading to version Y, please try the [released versions](https://github.com/cypress-io/code-coverage/releases) between X and Y to see where the breaking change was.

Diff for: common-utils.js

@@ -26,7 +26,44 @@ const defaultNycOptions = {
   excludeAfterRemap: false
 }
 
+/**
+ * Returns an object with placeholder properties for files we
+ * do not have coverage yet. The result can go into the coverage object
+ *
+ * @param {string} fullPath Filename
+ */
+const fileCoveragePlaceholder = (fullPath) => {
+  return {
+    path: fullPath,
+    statementMap: {},
+    fnMap: {},
+    branchMap: {},
+    s: {},
+    f: {},
+    b: {}
+  }
+}
+
+const isPlaceholder = (entry) => {
+  // when the file has been instrumented, its entry has "hash" property
+  return !('hash' in entry)
+}
+
+/**
+ * Given a coverage object with potential placeholder entries
+ * inserted instead of covered files, removes them. Modifies the object in place
+ */
+const removePlaceholders = (coverage) => {
+  Object.keys(coverage).forEach((key) => {
+    if (isPlaceholder(coverage[key])) {
+      delete coverage[key]
+    }
+  })
+}
+
 module.exports = {
   combineNycOptions,
-  defaultNycOptions
+  defaultNycOptions,
+  fileCoveragePlaceholder,
+  removePlaceholders
 }

Diff for: cypress/fixtures/coverage.json

@@ -0,0 +1,26 @@
+{
+  "/src/index.js": {
+    "path": "/src/index.js",
+    "statementMap": {
+      "0": {
+        "start": {
+          "line": 7,
+          "column": 0
+        },
+        "end": {
+          "line": 14,
+          "column": 2
+        }
+      }
+    },
+    "fnMap": {},
+    "branchMap": {},
+    "s": {
+      "0": 1
+    },
+    "f": {},
+    "b": {},
+    "_coverageSchema": "1a1c01bbd47fc00a2c39e90264f33305004495a9",
+    "hash": "46f2efd10038593ec768c6cc815a6d6ee2924243"
+  }
+}

Diff for: cypress/integration/combine-spec.js

@@ -1,3 +1,4 @@
+/// <reference types="Cypress" />
 const { combineNycOptions, defaultNycOptions } = require('../../common-utils')
 describe('Combine NYC options', () => {
   it('overrides defaults', () => {

Diff for: cypress/integration/merge-spec.js

@@ -0,0 +1,86 @@
+/// <reference types="Cypress" />
+const istanbul = require('istanbul-lib-coverage')
+const coverage = require('../fixtures/coverage.json')
+const {
+  fileCoveragePlaceholder,
+  removePlaceholders
+} = require('../../common-utils')
+
+/**
+ * Extracts just the data from the coverage map object
+ * @param {*} cm
+ */
+const coverageMapToCoverage = (cm) => {
+  return JSON.parse(JSON.stringify(cm))
+}
+
+describe('merging coverage', () => {
+  const filename = '/src/index.js'
+
+  before(() => {
+    expect(coverage, 'initial coverage has this file').to.have.property(
+      filename
+    )
+  })
+
+  it('combines an empty coverage object', () => {
+    const previous = istanbul.createCoverageMap({})
+    const coverageMap = istanbul.createCoverageMap(previous)
+    coverageMap.merge(Cypress._.cloneDeep(coverage))
+
+    const merged = coverageMapToCoverage(coverageMap)
+
+    expect(merged, 'merged coverage').to.deep.equal(coverage)
+  })
+
+  it('combines the same full coverage twice', () => {
+    const previous = istanbul.createCoverageMap(Cypress._.cloneDeep(coverage))
+    const coverageMap = istanbul.createCoverageMap(previous)
+    coverageMap.merge(Cypress._.cloneDeep(coverage))
+
+    const merged = coverageMapToCoverage(coverageMap)
+    // it is almost the same - only the statement count has been doubled
+    const expected = Cypress._.cloneDeep(coverage)
+    expected[filename].s[0] = 2
+    expect(merged, 'merged coverage').to.deep.equal(expected)
+  })
+
+  it('does not merge correctly placeholders', () => {
+    const coverageWithPlaceHolder = Cypress._.cloneDeep(coverage)
+    const placeholder = fileCoveragePlaceholder(filename)
+    coverageWithPlaceHolder[filename] = placeholder
+
+    expect(coverageWithPlaceHolder, 'placeholder').to.deep.equal({
+      [filename]: placeholder
+    })
+
+    // now lets merge full info
+    const previous = istanbul.createCoverageMap(coverageWithPlaceHolder)
+    const coverageMap = istanbul.createCoverageMap(previous)
+    coverageMap.merge(coverage)
+
+    const merged = coverageMapToCoverage(coverageMap)
+    const expected = Cypress._.cloneDeep(coverage)
+    // the merge against the placeholder without valid statement map
+    // removes the statement map and sets the counter to null
+    expected[filename].s = { 0: null }
+    expected[filename].statementMap = {}
+    // and no hashes :(
+    delete expected[filename].hash
+    delete expected[filename]._coverageSchema
+    expect(merged).to.deep.equal(expected)
+  })
+
+  it('removes placeholders', () => {
+    const inputCoverage = Cypress._.cloneDeep(coverage)
+    removePlaceholders(inputCoverage)
+    expect(inputCoverage, 'nothing to remove').to.deep.equal(coverage)
+
+    // add placeholder
+    const placeholder = fileCoveragePlaceholder(filename)
+    inputCoverage[filename] = placeholder
+
+    removePlaceholders(inputCoverage)
+    expect(inputCoverage, 'the placeholder has been removed').to.deep.equal({})
+  })
+})

Diff for: examples/all-files/cypress/plugins/index.js

@@ -1,5 +1,6 @@
 module.exports = (on, config) => {
   require('../../../../task')(on, config)
+  // instrument the specs and any source files loaded from specs
   on('file:preprocessor', require('../../../../use-babelrc'))
   return config
 }

Diff for: examples/all-files/package.json

@@ -1,6 +1,7 @@
 {
   "name": "example-all-files",
   "description": "Report all files",
+  "private": true,
   "scripts": {
     "start": "../../node_modules/.bin/parcel serve index.html",
     "start:windows": "npx bin-up parcel serve index.html",

Diff for: examples/placeholders/.babelrc

@@ -0,0 +1,3 @@
+{
+  "plugins": ["istanbul"]
+}

Diff for: examples/placeholders/cypress.json

@@ -0,0 +1,3 @@
+{
+  "fixturesFolder": false
+}

Diff for: examples/placeholders/cypress/integration/spec-a.js

@@ -0,0 +1,8 @@
+/// <reference types="cypress" />
+// this spec only loads "src/a" module
+import { myFunc } from '../../src/a.js'
+describe('spec-a', () => {
+  it('exercises src/a.js', () => {
+    expect(myFunc(), 'always returns 30').to.equal(30)
+  })
+})

Diff for: examples/placeholders/cypress/integration/spec-b.js

@@ -0,0 +1,10 @@
+/// <reference types="cypress" />
+// this spec loads "src/b" module
+import { anotherFunction } from '../../src/b.js'
+describe('spec-b', () => {
+  it('exercises src/b.js', () => {
+    expect(anotherFunction(), 'always returns hello backwards').to.equal(
+      'olleh'
+    )
+  })
+})

Diff for: examples/placeholders/cypress/plugins/index.js

@@ -0,0 +1,6 @@
+module.exports = (on, config) => {
+  require('../../../../task')(on, config)
+  // instrument the specs and any source files loaded from specs
+  on('file:preprocessor', require('../../../../use-babelrc'))
+  return config
+}

Diff for: examples/placeholders/cypress/support/index.js

@@ -0,0 +1 @@
+import '../../../../support'