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

docs/guide/workspace.md

@@ -231,6 +231,4 @@ 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

@@ -414,13 +414,15 @@ export class IstanbulCoverageProvider extends BaseCoverageProvider implements Co
     const cacheKey = new Date().getTime()
     const coverageMap = libCoverage.createCoverageMap({})
 
+    const transform = this.createUncoveredFileTransformer(this.ctx)
+
     // 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}`)
+      await transform(`${filename}?v=${cacheKey}`)
       const lastCoverage = this.instrumenter.lastFileCoverage()
       coverageMap.addFileCoverage(lastCoverage)
     }

packages/coverage-v8/src/provider.ts

@@ -368,6 +368,7 @@ export class V8CoverageProvider extends BaseCoverageProvider implements Coverage
     const transformResults = normalizeTransformResults(
       this.ctx.vitenode.fetchCache,
     )
+    const transform = this.createUncoveredFileTransformer(this.ctx)
 
     const allFiles = await this.testExclude.glob(this.ctx.config.root)
     let includedFiles = allFiles.map(file =>
@@ -401,7 +402,7 @@ export class V8CoverageProvider extends BaseCoverageProvider implements Coverage
           const { originalSource } = await this.getSources(
             filename.href,
             transformResults,
-            file => this.ctx.vitenode.transformRequest(file),
+            transform,
           )
 
           const coverage = {

packages/vitest/src/utils/coverage.ts

@@ -1,6 +1,7 @@
 import { relative } from 'pathe'
 import mm from 'micromatch'
 import type { CoverageMap } from 'istanbul-lib-coverage'
+import type { Vitest } from '../node/core'
 import type { BaseCoverageOptions, ResolvedCoverageOptions } from '../node/types/coverage'
 import { resolveCoverageReporters } from '../node/config/resolveConfig'
 
@@ -272,6 +273,37 @@ export class BaseCoverageProvider {
       return chunks
     }, [])
   }
+
+  createUncoveredFileTransformer(ctx: Vitest) {
+    const servers = [
+      ...ctx.projects.map(project => ({
+        root: project.config.root,
+        vitenode: project.vitenode,
+      })),
+      // Check core last as it will match all files anyway
+      { root: ctx.config.root, vitenode: ctx.vitenode },
+    ]
+
+    return async function transformFile(filename: string) {
+      let lastError
+
+      for (const { root, vitenode } of servers) {
+        if (!filename.startsWith(root)) {
+          continue
+        }
+
+        try {
+          return await vitenode.transformRequest(filename)
+        }
+        catch (error) {
+          lastError = error
+        }
+      }
+
+      // All vite-node servers failed to transform the file
+      throw lastError
+    }
+  }
 }
 
 /**

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

@@ -0,0 +1,78 @@
+import { readFileSync } from "node:fs";
+import { Plugin, defineWorkspace } from "vitest/config";
+import MagicString from "magic-string";
+
+export default defineWorkspace([
+  // Project that uses its own "root" and custom transform plugin
+  {
+    test: {
+      name: "custom-with-root",
+      root: "fixtures/workspaces/custom-2",
+    },
+    plugins: [customFilePlugin("2")],
+  },
+
+  // Project that cannot transform "*.custom-x" files
+  {
+    test: {
+      name: "normal",
+      include: ["fixtures/test/math.test.ts"],
+    },
+  },
+
+  // Project that uses default "root" and has custom transform plugin
+  {
+    test: {
+      name: "custom",
+      include: ["fixtures/test/custom-1-syntax.test.ts"],
+    },
+    plugins: [customFilePlugin("1")],
+  },
+]);
+
+/**
+ * Plugin for transforming `.custom-1` and/or `.custom-2` files to Javascript
+ */
+function customFilePlugin(postfix: "1" | "2"): Plugin {
+  function transform(code: MagicString) {
+    code.replaceAll(
+      "<function covered>",
+      `
+function covered() {
+  return "Custom-${postfix} file loaded!"
+}
+  `.trim()
+    );
+
+    code.replaceAll(
+      "<function uncovered>",
+      `
+function uncovered() {
+  return "This should be uncovered!"
+}
+    `.trim()
+    );
+
+    code.replaceAll("<default export covered>", "export default covered()");
+    code.replaceAll("<default export uncovered>", "export default uncovered()");
+  }
+
+  return {
+    name: `custom-${postfix}-file-plugin`,
+    transform(_, id) {
+      const filename = id.split("?")[0];
+
+      if (filename.endsWith(`.custom-${postfix}`)) {
+        const content = readFileSync(filename, "utf8");
+
+        const s = new MagicString(content);
+        transform(s);
+
+        return {
+          code: s.toString(),
+          map: s.generateMap({ hires: "boundary" }),
+        };
+      }
+    },
+  };
+}

test/coverage-test/fixtures/src/covered.custom-1

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

test/coverage-test/fixtures/src/uncovered.custom-1

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

test/coverage-test/fixtures/test/custom-1-syntax.test.ts

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

test/coverage-test/fixtures/workspaces/custom-2/src/covered.custom-2

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

test/coverage-test/fixtures/workspaces/custom-2/src/uncovered.custom-2

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

test/coverage-test/fixtures/workspaces/custom-2/test/custom-2-syntax.test.ts

@@ -0,0 +1,8 @@
+import { expect, test } from 'vitest'
+
+// @ts-expect-error -- untyped
+import output from '../src/covered.custom-2'
+
+test('custom-2 file loads fine', () => {
+  expect(output).toMatch('Custom-2 file loaded!')
+})

test/coverage-test/test/__snapshots__/custom-file-covered-1-istanbul.snapshot.json

@@ -0,0 +1,83 @@
+{
+  "path": "<process-cwd>/fixtures/src/covered.custom-1",
+  "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": {}
+}