fix: reset istanbul coverage between runs

src/api.ts

@@ -194,6 +194,10 @@ export class VitestFolderAPI {
     return this.meta.rpc.waitForCoverageReport()
   }
 
+  async invalidateIstanbulTestModules(modules: string[] | null) {
+    await this.meta.rpc.invalidateIstanbulTestModules(modules)
+  }
+
   async enableCoverage() {
     await this.meta.rpc.enableCoverage()
   }

src/api/rpc.ts

@@ -18,6 +18,7 @@ export interface VitestMethods {
   watchTests: (files?: SerializedTestSpecification[] | string[], testNamePattern?: string) => void
   unwatchTests: () => void
 
+  invalidateIstanbulTestModules: (modules: string[] | null) => Promise<void>
   enableCoverage: () => void
   disableCoverage: () => void
   waitForCoverageReport: () => Promise<string | null>

src/runner/runner.ts

@@ -222,6 +222,16 @@ export class TestRunner extends vscode.Disposable {
       }),
     )
 
+    const modules = !request.include
+      ? null
+      : getTestFiles(request.include).map((f) => {
+        if (typeof f === 'string') {
+          return f
+        }
+        return f[1]
+      })
+
+    await this.api.invalidateIstanbulTestModules(modules)
     await this.runTests(request, token)
   }
 

src/worker/vitest.ts

@@ -301,6 +301,23 @@ export class Vitest implements VitestMethods {
       this.watcher.trackEveryFile()
   }
 
+  // we need to invalidate the modules because Vitest caches the code injected by istanbul
+  async invalidateIstanbulTestModules(modules: string[] | null) {
+    if (!this.coverage.enabled || this.coverage.config.provider !== 'istanbul') {
+      return
+    }
+    if (!modules) {
+      this.ctx.server.moduleGraph.invalidateAll()
+      return
+    }
+    modules.forEach((moduleId) => {
+      const mod = this.ctx.server.moduleGraph.getModuleById(moduleId)
+      if (mod) {
+        this.invalidateTree(mod)
+      }
+    })
+  }
+
   disableCoverage() {
     return this.coverage.disable()
   }