feat(experimental): add printImportBreakdown.limit (fix: trim importDurations data)

packages/ui/client/components/views/ViewModuleGraph.vue

@@ -56,7 +56,7 @@ const breakdownIconClass = computed(() => {
   }
   return textClass
 })
-const breakdownShow = ref(config.value?.experimental?.printImportBreakdown ?? breakdownIconClass.value === 'text-red')
+const breakdownShow = ref(config.value?.experimental?.printImportBreakdown?.enabled ?? breakdownIconClass.value === 'text-red')
 
 onMounted(() => {
   filteredGraph.value = filterGraphByLevels(graph.value, null, 2)

packages/vitest/src/node/cli/cli-config.ts

@@ -777,6 +777,22 @@ export const cliOptionsConfig: VitestCLIOptions = {
       openTelemetry: null,
       printImportBreakdown: {
         description: 'Print import breakdown after the summary. If the reporter doesn\'t support summary, this will have no effect. Note that UI\'s "Module Graph" tab always has an import breakdown.',
+        argument: '',
+        transform(value) {
+          if (typeof value === 'boolean') {
+            return { enabled: value }
+          }
+          return value
+        },
+        subcommands: {
+          enabled: {
+            description: 'Enable import breakdown display (default: false).',
+          },
+          limit: {
+            description: 'Number of imports to show in CLI output (default: 10). Set to 0 to disable import duration collection entirely.',
+            argument: '<number>',
+          },
+        },
       },
     },
   },

packages/vitest/src/node/config/resolveConfig.ts

@@ -802,7 +802,7 @@ export function resolveConfig(
   resolved.testTimeout ??= resolved.browser.enabled ? 15_000 : 5_000
   resolved.hookTimeout ??= resolved.browser.enabled ? 30_000 : 10_000
 
-  resolved.experimental ??= {}
+  resolved.experimental ??= {} as any
   if (resolved.experimental.openTelemetry?.sdkPath) {
     const sdkPath = resolve(
       resolved.root,
@@ -823,6 +823,9 @@ export function resolveConfig(
       resolved.experimental.fsModuleCachePath,
     )
   }
+  resolved.experimental.printImportBreakdown ??= {} as any
+  resolved.experimental.printImportBreakdown.enabled ??= false
+  resolved.experimental.printImportBreakdown.limit ??= 10
 
   return resolved
 }

packages/vitest/src/node/reporters/base.ts

@@ -607,7 +607,7 @@ export abstract class BaseReporter implements Reporter {
       }
     }
 
-    if (this.ctx.config.experimental.printImportBreakdown) {
+    if (this.ctx.config.experimental.printImportBreakdown.enabled) {
       this.printImportsBreakdown()
     }
 
@@ -649,14 +649,15 @@ export abstract class BaseReporter implements Reporter {
 
     const sortedImports = allImports.sort((a, b) => b.totalTime - a.totalTime)
     const maxTotalTime = sortedImports[0].totalTime
-    const topImports = sortedImports.slice(0, 10)
+    const limit = this.ctx.config.experimental.printImportBreakdown.limit
+    const topImports = sortedImports.slice(0, limit)
 
     const totalSelfTime = allImports.reduce((sum, imp) => sum + imp.selfTime, 0)
     const totalTotalTime = allImports.reduce((sum, imp) => sum + imp.totalTime, 0)
     const slowestImport = sortedImports[0]
 
     this.log()
-    this.log(c.bold('Import Duration Breakdown') + c.dim(' (ordered by Total Time) (Top 10)'))
+    this.log(c.bold('Import Duration Breakdown') + c.dim(` (ordered by Total Time) (Top ${limit})`))
 
     // if there are multiple files, it's highly possible that some of them will import the same large file
     // we group them to show the distinction between those files more easily

packages/vitest/src/node/types/config.ts

@@ -850,11 +850,23 @@ export interface InlineConfig {
       browserSdkPath?: string
     }
     /**
-     * Show imports (top 10) that take a long time.
+     * Show imports that take a long time.
      *
      * Enabling this will also show a breakdown by default in UI, but you can always press a button to toggle it.
      */
-    printImportBreakdown?: boolean
+    printImportBreakdown?: {
+      /**
+       * Enable import breakdown display in CLI output.
+       * @default false
+       */
+      enabled?: boolean
+      /**
+       * Number of imports to show in CLI output.
+       * Set to 0 to disable import duration collection entirely.
+       * @default 10
+       */
+      limit?: number
+    }
   }
 }
 
@@ -1093,6 +1105,13 @@ export interface ResolvedConfig
 
   vmMemoryLimit?: UserConfig['vmMemoryLimit']
   dumpDir?: string
+
+  experimental: Omit<Required<UserConfig>['experimental'], 'printImportBreakdown'> & {
+    printImportBreakdown: {
+      enabled: boolean
+      limit: number
+    }
+  }
 }
 
 type NonProjectOptions

packages/vitest/src/runtime/config.ts

@@ -119,7 +119,10 @@ export interface SerializedConfig {
   serializedDefines: string
   experimental: {
     fsModuleCache: boolean
-    printImportBreakdown: boolean | undefined
+    printImportBreakdown: {
+      enabled: boolean
+      limit: number
+    }
     openTelemetry: {
       enabled: boolean
       sdkPath?: string

packages/vitest/src/runtime/runners/test.ts

@@ -227,10 +227,25 @@ export class VitestTestRunner implements VitestRunner {
   }
 
   getImportDurations(): Record<string, ImportDuration> {
-    const importDurations: Record<string, ImportDuration> = {}
-    const entries = this.workerState.moduleExecutionInfo?.entries() || []
+    const { limit } = this.config.experimental.printImportBreakdown
+    // limit = 0 means opt-out from collection entirely
+    if (limit === 0) {
+      return {}
+    }
+
+    const entries = [...(this.workerState.moduleExecutionInfo?.entries() || [])]
 
-    for (const [filepath, { duration, selfTime, external, importer }] of entries) {
+    // Trim to top N by duration to reduce IPC payload
+    // Keep enough entries for UI "show more" and aggregation
+    const retention = Math.max(50, limit * 5)
+
+    // Sort by duration descending and keep top entries
+    const sortedEntries = entries
+      .sort(([, a], [, b]) => b.duration - a.duration)
+      .slice(0, retention)
+
+    const importDurations: Record<string, ImportDuration> = {}
+    for (const [filepath, { duration, selfTime, external, importer }] of sortedEntries) {
       importDurations[normalize(filepath)] = {
         selfTime,
         totalTime: duration,

test/reporters/tests/import-durations.test.ts

@@ -74,4 +74,37 @@ describe('import durations', () => {
     expect(file.importDurations?.[throwsFile]?.totalTime).toBeGreaterThanOrEqual(24)
     expect(file.importDurations?.[throwsFile]?.selfTime).toBeGreaterThanOrEqual(24)
   })
+
+  it('should print import breakdown when enabled', async () => {
+    const { stdout } = await runVitest({
+      root,
+      include: ['**/import-durations.test.ts'],
+      experimental: {
+        printImportBreakdown: {
+          enabled: true,
+          limit: 5,
+        },
+      },
+    })
+
+    expect(stdout).toContain('Import Duration Breakdown')
+    expect(stdout).toContain('(ordered by Total Time)')
+    expect(stdout).toContain('Total imports:')
+    expect(stdout).toContain('(Top 5)')
+  })
+
+  it('should not collect importDurations when limit is 0', async () => {
+    const { ctx } = await runVitest({
+      root,
+      include: ['**/import-durations.test.ts'],
+      experimental: {
+        printImportBreakdown: {
+          limit: 0,
+        },
+      },
+    })
+
+    const file = ctx!.state.getFiles()[0]
+    expect(file.importDurations).toEqual({})
+  })
 })