refactor: remove the need for "processSourceMap" (#18187)

Author: sheremet-va

docs/guide/api-environment.md

@@ -714,6 +714,10 @@ export interface ModuleRunnerOptions {
 
 ```ts
 export interface ModuleEvaluator {
+  /**
+   * Number of prefixed lines in the transformed code.
+   */
+  startOffset?: number
   /**
    * Evaluate code that was transformed by Vite.
    * @param context Function context
@@ -733,7 +737,7 @@ export interface ModuleEvaluator {
 }
 ```
 
-Vite exports `ESModulesEvaluator` that implements this interface by default. It uses `new AsyncFunction` to evaluate code, so if the code has inlined source map it should contain an [offset of 2 lines](https://tc39.es/ecma262/#sec-createdynamicfunction) to accommodate for new lines added. This is done automatically in the server node environment. If your runner implementation doesn't have this constraint, you should use `fetchModule` (exported from `vite`) directly.
+Vite exports `ESModulesEvaluator` that implements this interface by default. It uses `new AsyncFunction` to evaluate code, so if the code has inlined source map it should contain an [offset of 2 lines](https://tc39.es/ecma262/#sec-createdynamicfunction) to accommodate for new lines added. This is done automatically by the `ESModulesEvaluator`. Custom evaluators will not add additional lines.
 
 ## RunnerTransport
 

packages/vite/src/module-runner/esmEvaluator.ts

@@ -1,4 +1,7 @@
-import { AsyncFunction } from '../shared/utils'
+import {
+  AsyncFunction,
+  asyncFunctionDeclarationPaddingLineCount,
+} from '../shared/utils'
 import {
   ssrDynamicImportKey,
   ssrExportAllKey,
@@ -9,6 +12,8 @@ import {
 import type { ModuleEvaluator, ModuleRunnerContext } from './types'
 
 export class ESModulesEvaluator implements ModuleEvaluator {
+  startOffset = asyncFunctionDeclarationPaddingLineCount
+
   async runInlinedModule(
     context: ModuleRunnerContext,
     code: string,

packages/vite/src/module-runner/runner.ts

@@ -265,6 +265,7 @@ export class ModuleRunner {
           ? { externalize: url, type: 'builtin' }
           : await this.transport.fetchModule(url, importer, {
               cached: isCached,
+              startOffset: this.evaluator.startOffset,
             })
       ) as ResolvedResult
 

packages/vite/src/module-runner/types.ts

@@ -46,6 +46,10 @@ export interface ModuleRunnerContext {
 }
 
 export interface ModuleEvaluator {
+  /**
+   * Number of prefixed lines in the transformed code.
+   */
+  startOffset?: number
   /**
    * Run code that was transformed by Vite.
    * @param context Function context
@@ -138,6 +142,7 @@ export type FetchFunction = (
 
 export interface FetchFunctionOptions {
   cached?: boolean
+  startOffset?: number
 }
 
 export interface ModuleRunnerHmr {

packages/vite/src/node/server/environments/nodeEnvironment.ts

@@ -1,7 +1,6 @@
 import type { ResolvedConfig } from '../../config'
 import type { DevEnvironmentContext } from '../environment'
 import { DevEnvironment } from '../environment'
-import { asyncFunctionDeclarationPaddingLineCount } from '../../../shared/utils'
 
 export function createNodeDevEnvironment(
   name: string,
@@ -14,17 +13,5 @@ export function createNodeDevEnvironment(
     )
   }
 
-  return new DevEnvironment(name, config, {
-    ...context,
-    runner: {
-      processSourceMap(map) {
-        // this assumes that "new AsyncFunction" is used to create the module
-        return Object.assign({}, map, {
-          mappings:
-            ';'.repeat(asyncFunctionDeclarationPaddingLineCount) + map.mappings,
-        })
-      },
-      ...context.runner,
-    },
-  })
+  return new DevEnvironment(name, config, context)
 }

packages/vite/src/node/ssr/fetchModule.ts

@@ -15,7 +15,7 @@ import { normalizeResolvedIdToUrl } from '../plugins/importAnalysis'
 export interface FetchModuleOptions {
   cached?: boolean
   inlineSourceMap?: boolean
-  processSourceMap?<T extends NonNullable<TransformResult['map']>>(map: T): T
+  startOffset?: number
 }
 
 /**
@@ -127,7 +127,7 @@ export async function fetchModule(
   }
 
   if (options.inlineSourceMap !== false) {
-    result = inlineSourceMap(mod, result, options.processSourceMap)
+    result = inlineSourceMap(mod, result, options.startOffset)
   }
 
   // remove shebang
@@ -150,7 +150,7 @@ const OTHER_SOURCE_MAP_REGEXP = new RegExp(
 function inlineSourceMap(
   mod: EnvironmentModuleNode,
   result: TransformResult,
-  processSourceMap?: FetchModuleOptions['processSourceMap'],
+  startOffset: number | undefined,
 ) {
   const map = result.map
   let code = result.code
@@ -167,7 +167,11 @@ function inlineSourceMap(
   if (OTHER_SOURCE_MAP_REGEXP.test(code))
     code = code.replace(OTHER_SOURCE_MAP_REGEXP, '')
 
-  const sourceMap = processSourceMap?.(map) || map
+  const sourceMap = startOffset
+    ? Object.assign({}, map, {
+        mappings: ';'.repeat(startOffset) + map.mappings,
+      })
+    : map
   result.code = `${code.trimEnd()}\n//# sourceURL=${
     mod.id
   }\n${MODULE_RUNNER_SOURCEMAPPING_SOURCE}\n//# ${SOURCEMAPPING_URL}=${genSourceMapUrl(sourceMap)}\n`