perf: avoid sourcemap generation during dev for line-stable transforms

Author: patak-dev

packages/vite/src/node/plugins/assetImportMetaUrl.ts

@@ -3,7 +3,7 @@ import MagicString from 'magic-string'
 import { stripLiteral } from 'strip-literal'
 import type { Plugin } from '../plugin'
 import type { ResolvedConfig } from '../config'
-import { transformResult } from '../utils'
+import { transformStableResult } from '../utils'
 import { fileToUrl } from './asset'
 import { preloadHelperId } from './importAnalysisBuild'
 
@@ -81,7 +81,7 @@ export function assetImportMetaUrlPlugin(config: ResolvedConfig): Plugin {
           )
         }
         if (s) {
-          return transformResult(s, id, config)
+          return transformStableResult(s, id, config)
         }
       }
       return null

packages/vite/src/node/plugins/dynamicImportVars.ts

@@ -11,7 +11,7 @@ import {
   normalizePath,
   parseRequest,
   requestQuerySplitRE,
-  transformResult
+  transformStableResult
 } from '../utils'
 
 export const dynamicImportHelperId = '/@vite/dynamic-import-helper'
@@ -209,7 +209,7 @@ export function dynamicImportVarsPlugin(config: ResolvedConfig): Plugin {
             `import __variableDynamicImportRuntimeHelper from "${dynamicImportHelperId}";`
           )
         }
-        return transformResult(s, importer, config)
+        return transformStableResult(s, importer, config)
       }
     }
   }

packages/vite/src/node/plugins/importAnalysis.ts

@@ -40,7 +40,7 @@ import {
   removeImportQuery,
   stripBomTag,
   timeFrom,
-  transformResult,
+  transformStableResult,
   unwrapId
 } from '../utils'
 import type { ResolvedConfig } from '../config'
@@ -711,7 +711,7 @@ export function importAnalysisPlugin(config: ResolvedConfig): Plugin {
       }
 
       if (s) {
-        return transformResult(s, importer, config)
+        return transformStableResult(s, importer, config)
       } else {
         return source
       }

packages/vite/src/node/plugins/importMetaGlob.ts

@@ -17,7 +17,7 @@ import type { Plugin } from '../plugin'
 import type { ViteDevServer } from '../server'
 import type { ModuleNode } from '../server/moduleGraph'
 import type { ResolvedConfig } from '../config'
-import { normalizePath, slash, transformResult } from '../utils'
+import { normalizePath, slash, transformStableResult } from '../utils'
 
 const { isMatch, scan } = micromatch
 
@@ -75,7 +75,7 @@ export function importGlobPlugin(config: ResolvedConfig): Plugin {
             server!.watcher.add(dirname(file))
           })
         }
-        return transformResult(result.s, id, config)
+        return transformStableResult(result.s, id, config)
       }
     }
   }

packages/vite/src/node/plugins/workerImportMetaUrl.ts

@@ -10,7 +10,7 @@ import {
   injectQuery,
   normalizePath,
   parseRequest,
-  transformResult
+  transformStableResult
 } from '../utils'
 import { getDepsOptimizer } from '../optimizer'
 import type { WorkerType } from './worker'
@@ -136,7 +136,7 @@ export function workerImportMetaUrlPlugin(config: ResolvedConfig): Plugin {
         }
 
         if (s) {
-          return transformResult(s, id, config)
+          return transformStableResult(s, id, config)
         }
 
         return null

packages/vite/src/node/utils.ts

@@ -1028,16 +1028,20 @@ function normalizeSingleAlias({
   return alias
 }
 
-export function transformResult(
+/**
+ * Transforms transpiled code result where line numbers aren't altered,
+ * so we can skip sourcemap generation during dev
+ */
+export function transformStableResult(
   s: MagicString,
   id: string,
   config: ResolvedConfig
 ): TransformResult {
-  const isBuild = config.command === 'build'
-  const needSourceMap = !isBuild || config.build.sourcemap
   return {
     code: s.toString(),
-    map: needSourceMap ? s.generateMap({ hires: true, source: id }) : null
+    map: config.build.sourcemap
+      ? s.generateMap({ hires: true, source: id })
+      : null
   }
 }