fix: absolute: true source maps will preserve source content

lib/map-generator.js

@@ -16,6 +16,7 @@ class MapGenerator {
     this.root = root
     this.opts = opts
     this.css = cssString
+    this.usesFileUrls = !this.mapOpts.from && this.mapOpts.absolute
   }
 
   isMap() {
@@ -97,10 +98,10 @@ class MapGenerator {
           let from = node.source.input.from
           if (from && !already[from]) {
             already[from] = true
-            this.map.setSourceContent(
-              this.toUrl(this.path(from)),
-              node.source.input.css
-            )
+            let fromUrl = this.usesFileUrls
+              ? this.toFileUrl(from)
+              : this.toUrl(this.path(from))
+            this.map.setSourceContent(fromUrl, node.source.input.css)
           }
         }
       })
@@ -232,17 +233,21 @@ class MapGenerator {
     return encodeURI(path).replace(/[#?]/g, encodeURIComponent)
   }
 
+  toFileUrl(path) {
+    if (pathToFileURL) {
+      return pathToFileURL(path).toString()
+    } else {
+      throw new Error(
+        '`map.absolute` option is not available in this PostCSS build'
+      )
+    }
+  }
+
   sourcePath(node) {
     if (this.mapOpts.from) {
       return this.toUrl(this.mapOpts.from)
-    } else if (this.mapOpts.absolute) {
-      if (pathToFileURL) {
-        return pathToFileURL(node.source.input.from).toString()
-      } else {
-        throw new Error(
-          '`map.absolute` option is not available in this PostCSS build'
-        )
-      }
+    } else if (this.usesFileUrls) {
+      return this.toFileUrl(node.source.input.from)
     } else {
       return this.toUrl(this.path(node.source.input.from))
     }

test/map.test.ts

@@ -2,6 +2,7 @@ import { SourceMapConsumer, SourceMapGenerator } from 'source-map-js'
 import { removeSync, outputFileSync } from 'fs-extra'
 import { is, type, equal, match } from 'uvu/assert'
 import { join, resolve, parse } from 'path'
+import { pathToFileURL } from 'url'
 import { existsSync } from 'fs'
 import { test } from 'uvu'
 
@@ -722,4 +723,18 @@ test('supports previous inline map with empty processor', () => {
   match((root3.source?.input.origin(1, 0) as any).file, 'a.css')
 })
 
+test('absolute sourcemaps have source contents', () => {
+  let result = postcss([() => {}]).process('a{}', {
+    from: '/dir/to/a.css',
+    map: {
+      inline: false,
+      absolute: true
+    }
+  })
+  equal(result.map.toJSON().sources, [
+    pathToFileURL('/dir/to/a.css').toString()
+  ])
+  equal(result.map.toJSON().sourcesContent, ['a{}'])
+})
+
 test.run()