fix(coverage): use project specific vitenode for uncovered files

docs/guide/workspace.md

@@ -185,6 +185,4 @@ All configuration options that are not supported inside a project config have <N
 
 ## Coverage
 
-Coverage for workspace projects works out of the box. But if you have [`all`](/config/#coverage-all) option enabled and use non-conventional extensions in some of your projects, you will need to have a plugin that handles this extension in your root configuration file.
-
-For example, if you have a package that uses Vue files and it has its own config file, but some of the files are not imported in your tests, coverage will fail trying to analyze the usage of unused files, because it relies on the root configuration rather than project configuration.
+Coverage for workspace projects works out of the box.

packages/coverage-istanbul/src/provider.ts

@@ -386,6 +386,11 @@ export class IstanbulCoverageProvider
       resolve(this.ctx.config.root, file),
     )
 
+    const viteNodeServers = [
+      this.ctx.vitenode,
+      ...this.ctx.projects.map(project => project.vitenode),
+    ]
+
     if (this.ctx.config.changed) {
       includedFiles = (this.ctx.config.related || []).filter(file =>
         includedFiles.includes(file),
@@ -396,16 +401,29 @@ export class IstanbulCoverageProvider
       .filter(file => !coveredFiles.includes(file))
       .sort()
 
-    const cacheKey = new Date().getTime()
     const coverageMap = libCoverage.createCoverageMap({})
 
+    // Make sure file is not served from cache so that instrumenter loads up requested file coverage
+    const cacheKey = new Date().getTime()
+
     // Note that these cannot be run parallel as synchronous instrumenter.lastFileCoverage
     // returns the coverage of the last transformed file
     for (const [index, filename] of uncoveredFiles.entries()) {
       debug('Uncovered file %s %d/%d', filename, index, uncoveredFiles.length)
 
-      // Make sure file is not served from cache so that instrumenter loads up requested file coverage
-      await this.ctx.vitenode.transformRequest(`${filename}?v=${cacheKey}`)
+      for (const vitenode of viteNodeServers) {
+        try {
+          await vitenode.transformRequest(`${filename}?v=${cacheKey}`)
+          continue
+        }
+        catch (error) {
+          // Try transforming with next ViteNode server, unless last
+          if (viteNodeServers.indexOf(vitenode) === viteNodeServers.length - 1) {
+            throw error
+          }
+        }
+      }
+
       const lastCoverage = this.instrumenter.lastFileCoverage()
       coverageMap.addFileCoverage(lastCoverage)
     }

packages/coverage-v8/src/provider.ts

@@ -450,6 +450,11 @@ export class V8CoverageProvider
     }> {
     const filePath = normalize(fileURLToPath(url))
 
+    const viteNodeServers = [
+      this.ctx.vitenode,
+      ...this.ctx.projects.map(project => project.vitenode),
+    ]
+
     let isExecuted = true
     let transformResult:
       | FetchResult
@@ -458,9 +463,18 @@ export class V8CoverageProvider
 
     if (!transformResult) {
       isExecuted = false
-      transformResult = await this.ctx.vitenode
-        .transformRequest(filePath)
-        .catch(() => null)
+      for (const vitenode of viteNodeServers) {
+        try {
+          transformResult = await vitenode.transformRequest(filePath)
+          continue
+        }
+        catch (error) {
+          // Try transforming with next ViteNode server, unless last
+          if (viteNodeServers.indexOf(vitenode) === viteNodeServers.length - 1) {
+            throw error
+          }
+        }
+      }
     }
 
     const map = transformResult?.map as EncodedSourceMap | undefined

test/coverage-test/fixtures/configs/vitest.workspace.multi-transforms.ts

@@ -0,0 +1,67 @@
+import { Plugin, defineWorkspace } from "vitest/config"
+import MagicString from "magic-string"
+import { readFileSync } from "fs"
+
+export default defineWorkspace([
+  {
+    test: {
+      name: "normal",
+      include: ["fixtures/test/math.test.ts"],
+    },
+  },
+  {
+    test: {
+      name: "special",
+      include: ["fixtures/test/custom-syntax.test.ts"],
+    },
+    plugins: [customFilePlugin()],
+  },
+])
+
+/**
+ * Plugin for transforming `.custom` files to Javascript
+ */
+function customFilePlugin(): Plugin {
+  return {
+    name: "custom-file-plugin",
+    transform(_, id) {
+      const filename = id.split("?")[0]
+
+      if (filename.endsWith(".custom")) {
+        const content = readFileSync(filename, "utf8")
+
+        const s = new MagicString(content)
+        transformCustomLang(s)
+
+        return {
+          code: s.toString(),
+          map: s.generateMap({ hires: "boundary" }),
+        }
+      }
+    },
+  }
+}
+
+// Syntax of custom-language
+function transformCustomLang(code: MagicString) {
+  code.replaceAll(
+    "<function covered>",
+    `
+function covered() {
+  return "Custom file loaded!"
+}
+  `.trim()
+  )
+
+  code.replaceAll(
+    "<function uncovered>",
+    `
+function uncovered() {
+  return "This should be uncovered!"
+}
+    `.trim()
+  )
+
+  code.replaceAll("<default export covered>", "export default covered()")
+  code.replaceAll("<default export uncovered>", "export default uncovered()")
+}

test/coverage-test/fixtures/src/covered.custom

@@ -0,0 +1,5 @@
+<function covered>
+
+<function uncovered>
+
+<default export covered>

test/coverage-test/fixtures/src/uncovered.custom

@@ -0,0 +1,3 @@
+<function uncovered>
+
+<default export uncovered>

test/coverage-test/fixtures/test/custom-syntax.test.ts

@@ -0,0 +1,8 @@
+import { expect, test } from 'vitest'
+
+// @ts-expect-error -- untyped
+import output from '../src/covered.custom'
+
+test('custom file loads fine', () => {
+  expect(output).toMatch('Custom file loaded!')
+})

test/coverage-test/test/__snapshots__/custom-file-covered-istanbul.snapshot.json

@@ -0,0 +1,83 @@
+{
+  "path": "<process-cwd>/fixtures/src/covered.custom",
+  "statementMap": {
+    "0": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 18
+      }
+    },
+    "1": {
+      "start": {
+        "line": 3,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 20
+      }
+    }
+  },
+  "fnMap": {
+    "0": {
+      "name": "covered",
+      "decl": {
+        "start": {
+          "line": 1,
+          "column": 0
+        },
+        "end": {
+          "line": 1,
+          "column": 18
+        }
+      },
+      "loc": {
+        "start": {
+          "line": 1,
+          "column": 0
+        },
+        "end": {
+          "line": 1,
+          "column": 18
+        }
+      }
+    },
+    "1": {
+      "name": "uncovered",
+      "decl": {
+        "start": {
+          "line": 3,
+          "column": 0
+        },
+        "end": {
+          "line": 3,
+          "column": 20
+        }
+      },
+      "loc": {
+        "start": {
+          "line": 3,
+          "column": 0
+        },
+        "end": {
+          "line": 3,
+          "column": 20
+        }
+      }
+    }
+  },
+  "branchMap": {},
+  "s": {
+    "0": 1,
+    "1": 0
+  },
+  "f": {
+    "0": 1,
+    "1": 0
+  },
+  "b": {}
+}