fix(coverage): flaky c8 coverage caused by parallel sourcemap constructing (#2591)

Co-authored-by: Vladimir <sleuths.slews0s@icloud.com>
Fixes undefined

Author: AriPerkkio

packages/coverage-c8/src/provider.ts

@@ -48,39 +48,61 @@ export class C8CoverageProvider implements CoverageProvider {
     takeCoverage()
     const report = createReport(this.ctx.config.coverage)
 
+    interface MapAndSource { map: RawSourceMap; source: string | undefined }
+    type SourceMapMeta = { url: string; filepath: string } & MapAndSource
+
     // add source maps
-    const sourceMapMeta: Record<string, { map: RawSourceMap; source: string | undefined }> = {}
-    await Promise.all(Array
+    const sourceMapMeta: Record<SourceMapMeta['url'], MapAndSource> = {}
+
+    const entries = Array
       .from(this.ctx.vitenode.fetchCache.entries())
       .filter(i => !i[0].includes('/node_modules/'))
-      .map(async ([file, { result }]) => {
-        const map = result.map
-        if (!map)
-          return
+      .map(([file, { result }]) => {
+        if (!result.map)
+          return null
 
         const filepath = file.split('?')[0]
 
-        const url = _url.pathToFileURL(filepath).href
-
-        let code: string | undefined
-        try {
-          code = (await fs.readFile(filepath)).toString()
-        }
-        catch { }
-
-        // Vite does not report full path in sourcemap sources
-        // so use an actual file path
-        const sources = [url]
-
-        sourceMapMeta[url] = {
+        return {
+          filepath,
+          url: _url.pathToFileURL(filepath).href,
+          map: result.map,
           source: result.code,
-          map: {
-            sourcesContent: code ? [code] : undefined,
-            ...map,
-            sources,
-          },
         }
-      }))
+      })
+      .filter((entry) => {
+        if (!entry)
+          return false
+
+        // Mappings and sourcesContent are needed for C8 to work
+        return (
+          entry.map.mappings.length > 0
+          && entry.map.sourcesContent
+          && entry.map.sourcesContent.length > 0
+          && entry.map.sourcesContent[0].length > 0
+        )
+      }) as SourceMapMeta[]
+
+    await Promise.all(entries.map(async ({ url, source, map, filepath }) => {
+      let code: string | undefined
+      try {
+        code = (await fs.readFile(filepath)).toString()
+      }
+      catch { }
+
+      // Vite does not report full path in sourcemap sources
+      // so use an actual file path
+      const sources = [url]
+
+      sourceMapMeta[url] = {
+        source,
+        map: {
+          sourcesContent: code ? [code] : undefined,
+          ...map,
+          sources,
+        },
+      }
+    }))
 
     // This is a magic number. It corresponds to the amount of code
     // that we add in packages/vite-node/src/client.ts:114 (vm.runInThisContext)

test/coverage-test/coverage-report-tests/__snapshots__/c8.report.test.ts.snap

@@ -809,19 +809,63 @@ exports[`c8 json report 1`] = `
   },
   "<process-cwd>/src/Defined.vue": {
     "all": false,
-    "b": {},
-    "branchMap": {},
+    "b": {
+      "0": [
+        0,
+      ],
+    },
+    "branchMap": {
+      "0": {
+        "line": 6,
+        "loc": {
+          "end": {
+            "column": 36,
+            "line": 8,
+          },
+          "start": {
+            "column": 33,
+            "line": 6,
+          },
+        },
+        "locations": [
+          {
+            "end": {
+              "column": 36,
+              "line": 8,
+            },
+            "start": {
+              "column": 33,
+              "line": 6,
+            },
+          },
+        ],
+        "type": "branch",
+      },
+    },
     "f": {},
     "fnMap": {},
     "path": "<process-cwd>/src/Defined.vue",
     "s": {
       "0": 1,
       "1": 1,
+      "10": 1,
+      "11": 1,
+      "12": 1,
+      "13": 1,
+      "14": 1,
+      "15": 1,
+      "16": 1,
+      "17": 1,
+      "18": 1,
+      "19": 1,
       "2": 1,
       "3": 1,
       "4": 1,
       "5": 1,
-      "6": 1,
+      "6": 0,
+      "7": 0,
+      "8": 1,
+      "9": 1,
     },
     "statementMap": {
       "0": {
@@ -844,9 +888,109 @@ exports[`c8 json report 1`] = `
           "line": 2,
         },
       },
+      "10": {
+        "end": {
+          "column": 10,
+          "line": 11,
+        },
+        "start": {
+          "column": 0,
+          "line": 11,
+        },
+      },
+      "11": {
+        "end": {
+          "column": 15,
+          "line": 12,
+        },
+        "start": {
+          "column": 0,
+          "line": 12,
+        },
+      },
+      "12": {
+        "end": {
+          "column": 11,
+          "line": 13,
+        },
+        "start": {
+          "column": 0,
+          "line": 13,
+        },
+      },
+      "13": {
+        "end": {
+          "column": 0,
+          "line": 14,
+        },
+        "start": {
+          "column": 0,
+          "line": 14,
+        },
+      },
+      "14": {
+        "end": {
+          "column": 90,
+          "line": 15,
+        },
+        "start": {
+          "column": 0,
+          "line": 15,
+        },
+      },
+      "15": {
+        "end": {
+          "column": 25,
+          "line": 16,
+        },
+        "start": {
+          "column": 0,
+          "line": 16,
+        },
+      },
+      "16": {
+        "end": {
+          "column": 6,
+          "line": 17,
+        },
+        "start": {
+          "column": 0,
+          "line": 17,
+        },
+      },
+      "17": {
+        "end": {
+          "column": 25,
+          "line": 18,
+        },
+        "start": {
+          "column": 0,
+          "line": 18,
+        },
+      },
+      "18": {
+        "end": {
+          "column": 1,
+          "line": 19,
+        },
+        "start": {
+          "column": 0,
+          "line": 19,
+        },
+      },
+      "19": {
+        "end": {
+          "column": 8,
+          "line": 20,
+        },
+        "start": {
+          "column": 0,
+          "line": 20,
+        },
+      },
       "2": {
         "end": {
-          "column": 9,
+          "column": 0,
           "line": 3,
         },
         "start": {
@@ -856,7 +1000,7 @@ exports[`c8 json report 1`] = `
       },
       "3": {
         "end": {
-          "column": 0,
+          "column": 31,
           "line": 4,
         },
         "start": {
@@ -866,7 +1010,7 @@ exports[`c8 json report 1`] = `
       },
       "4": {
         "end": {
-          "column": 10,
+          "column": 12,
           "line": 5,
         },
         "start": {
@@ -876,7 +1020,7 @@ exports[`c8 json report 1`] = `
       },
       "5": {
         "end": {
-          "column": 15,
+          "column": 34,
           "line": 6,
         },
         "start": {
@@ -886,14 +1030,44 @@ exports[`c8 json report 1`] = `
       },
       "6": {
         "end": {
-          "column": 11,
+          "column": 4,
           "line": 7,
         },
         "start": {
           "column": 0,
           "line": 7,
         },
       },
+      "7": {
+        "end": {
+          "column": 36,
+          "line": 8,
+        },
+        "start": {
+          "column": 0,
+          "line": 8,
+        },
+      },
+      "8": {
+        "end": {
+          "column": 9,
+          "line": 9,
+        },
+        "start": {
+          "column": 0,
+          "line": 9,
+        },
+      },
+      "9": {
+        "end": {
+          "column": 0,
+          "line": 10,
+        },
+        "start": {
+          "column": 0,
+          "line": 10,
+        },
+      },
     },
   },
   "<process-cwd>/src/Hello.vue": {