Batch coverage data sent to combineCoverage to prevent timeouts (#877)

Author: aantes-st

Diff for: .circleci/config.yml

@@ -146,6 +146,7 @@ workflows:
               jobname:
                 - all-files
                 - backend
+                - batch-send-coverage
                 - before-all-visit
                 - before-each-visit
                 - cra-e2e-and-ct
@@ -174,6 +175,7 @@ workflows:
             - test-code-coverage-plugin
             - test-all-files
             - test-backend
+            - test-batch-send-coverage
             - test-before-all-visit
             - test-before-each-visit
             - test-cra-e2e-and-ct

Diff for: README.md

@@ -549,14 +549,21 @@ Deeply nested objects will sometimes have `[object Object]` values printed. You
 DEBUG_DEPTH=10 DEBUG=code-coverage npm run dev
 ```
 
-### Common issues
+## 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.
 
 If you decide to open an issue in this repository, please fill in all information the [issue template](https://github.com/cypress-io/code-coverage/blob/master/.github/ISSUE_TEMPLATE/bug_report.md) asks for. The issues most likely to be resolved have debug logs, screenshots, and hopefully public repository links so we can try running the tests ourselves.
 
+### Coverage reporting timeouts
+
+If the plugin times out when sending coverage report data to be merged, this may be due to a very large
+report being sent across processes. You can batch the report by setting the `sendCoverageBatchSize` environment
+variable in your `cypress.config.js` file's 'env' section. Assign the variable an integer value representing
+the number of report keys to send per batch.
+
 ## Contributing
 
 You can test changes locally by running tests and confirming that the code coverage has been calculated and saved.

Diff for: support-utils.js

@@ -148,7 +148,19 @@ function fixSourcePaths(coverage) {
   })
 }
 
+/**
+ * Validates and returns the configured batch size for
+ * sending coverage to the backend
+ */
+function getSendCoverageBatchSize() {
+  const batchSize = Cypress.env('sendCoverageBatchSize')
+  const parsedBatchSize = parseInt(batchSize)
+  const isValid = !isNaN(parsedBatchSize) && parsedBatchSize > 0
+  return isValid ? parsedBatchSize : null
+}
+
 module.exports = {
   fixSourcePaths,
-  filterFilesFromCoverage
+  filterFilesFromCoverage,
+  getSendCoverageBatchSize
 }

Diff for: support.js

@@ -3,7 +3,10 @@
 
 const dayjs = require('dayjs')
 var duration = require('dayjs/plugin/duration')
-const { filterFilesFromCoverage } = require('./support-utils')
+const {
+  filterFilesFromCoverage,
+  getSendCoverageBatchSize
+} = require('./support-utils')
 
 dayjs.extend(duration)
 
@@ -16,10 +19,37 @@ const sendCoverage = (coverage, pathname = '/') => {
 
   const totalCoverage = filterFilesFromCoverage(coverage)
 
-  // stringify coverage object for speed
-  cy.task('combineCoverage', JSON.stringify(totalCoverage), {
-    log: false
-  })
+  const envBatchSize = getSendCoverageBatchSize()
+  const keys = Object.keys(totalCoverage)
+
+  if (envBatchSize && envBatchSize < keys.length) {
+    sendBatchCoverage(totalCoverage, envBatchSize)
+  } else {
+    cy.task('combineCoverage', JSON.stringify(totalCoverage), {
+      log: false
+    })
+  }
+}
+
+/**
+ * Sends collected code coverage object to the backend code
+ * in batches via "cy.task".
+ */
+const sendBatchCoverage = (totalCoverage, batchSize) => {
+  const keys = Object.keys(totalCoverage)
+
+  for (let i = 0; i < keys.length; i += batchSize) {
+    const batchKeys = keys.slice(i, i + batchSize)
+    const batchCoverage = {}
+
+    batchKeys.forEach((key) => {
+      batchCoverage[key] = totalCoverage[key]
+    })
+
+    cy.task('combineCoverage', JSON.stringify(batchCoverage), {
+      log: false
+    })
+  }
 }
 
 /**

Diff for: test-apps/batch-send-coverage/.babelrc

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

Diff for: test-apps/batch-send-coverage/README.md

@@ -0,0 +1,4 @@
+# Test Case: Batch Send Coverage
+This test app tests that all expected files are covered when using
+the `sendCoverageBatchSize` environment variable in the Cypress
+configuration file.

Diff for: test-apps/batch-send-coverage/cypress.config.js

@@ -0,0 +1,14 @@
+const { defineConfig } = require('cypress')
+
+module.exports = defineConfig({
+  fixturesFolder: false,
+  env: {
+    sendCoverageBatchSize: 1
+  },
+  e2e: {
+    setupNodeEvents(on, config) {
+      return require('./cypress/plugins/index.js')(on, config)
+    },
+    baseUrl: 'http://localhost:1234'
+  }
+})

Diff for: test-apps/batch-send-coverage/cypress/e2e/spec.cy.js

@@ -0,0 +1,24 @@
+/// <reference types="cypress" />
+it('works', () => {
+  cy.visit('/')
+  cy.contains('Page body')
+
+  cy.window()
+    .invoke('reverse', 'super')
+    .should('equal', 'repus')
+  
+  cy.window()
+    .invoke('numsTimesTwo', [1, 2, 3])
+    .should('deep.equal', [2, 4, 6])
+
+  cy.window()
+    .invoke('add', 2, 3)
+    .should('equal', 5)
+
+  cy.window()
+    .invoke('sub', 5, 2)
+    .should('equal', 3)
+
+  // application's code should be instrumented
+  cy.window().should('have.property', '__coverage__')
+})

Diff for: test-apps/batch-send-coverage/cypress/plugins/index.js

@@ -0,0 +1,4 @@
+module.exports = (on, config) => {
+  require('@cypress/code-coverage/task')(on, config)
+  return config
+}

Diff for: test-apps/batch-send-coverage/cypress/support/commands.js

@@ -0,0 +1 @@
+import '@cypress/code-coverage/support'

Diff for: test-apps/batch-send-coverage/cypress/support/e2e.js

@@ -0,0 +1 @@
+require('./commands')

Diff for: test-apps/batch-send-coverage/index.html

@@ -0,0 +1,17 @@
+<body>
+  Page body
+  <script src="main.js"></script>
+  <script src="second.js"></script>
+  <script src="third.js"></script>
+    // use functions creates in "main.js"
+    if (add(2, 3) !== 5) {
+      throw new Error('wrong addition')
+    }
+    if (sub(2, 3) !== -1) {
+      throw new Error('wrong subtraction')
+    }
+    if (reverse('foo') !== 'oof') {
+      throw new Error('wrong string reverse')
+    }
+  </script>
+</body>

Diff for: test-apps/batch-send-coverage/main.js

@@ -0,0 +1,3 @@
+window.add = (a, b) => a + b
+
+window.sub = (a, b) => a - b