Support --pkg-importer=node (#267)

* Support --pkg-importer=node

* Code review

CHANGELOG.md

@@ -1,3 +1,10 @@
+## 2.3.0
+
+* Add a `--pkg-importer` flag to enable loading dependencies from `pkg:` URLs
+  with the same behavior as the compiler. Currently this only supports the
+  Node.js package resolution algorithm, via `--pkg-importer=node`. For example,
+  `@use "pkg:bootstrap"` will load `node_modules/bootstrap/scss/bootstrap.scss`.
+
 ## 2.2.1
 
 ### Module Migrator

lib/src/migrator.dart

@@ -68,9 +68,11 @@ abstract class Migrator extends Command<Map<Uri, String>> {
   Map<Uri, String> run() {
     var allMigrated = <Uri, String>{};
     var importer = FilesystemImporter('.');
-    var importCache = ImportCache(
-        importers: [NodeModulesImporter()],
-        loadPaths: globalResults!['load-path']);
+    var importCache = ImportCache(importers: [
+      NodeModulesImporter(),
+      for (var item in globalResults!['pkg-importer'] as List<String>)
+        if (item == 'node') NodePackageImporter('.')
+    ], loadPaths: globalResults!['load-path']);
 
     var entrypoints = [
       for (var argument in argResults!.rest)

lib/src/migrators/module/reference_source.dart

@@ -49,8 +49,8 @@ class ImportSource extends ReferenceSource {
   /// Returns the preferred namespace to use for this module, based on
   /// [originalRuleUrl].
   String get preferredNamespace {
-    var path = url.path;
-    var basename = p.url.basenameWithoutExtension(url.path);
+    var path = (originalRuleUrl ?? url).path;
+    var basename = p.url.basenameWithoutExtension(path);
     if (basename == 'index' || basename == '_index') path = p.url.dirname(path);
     return namespaceForPath(path);
   }

lib/src/runner.dart

@@ -9,12 +9,12 @@ import 'dart:isolate';
 import 'package:args/args.dart';
 import 'package:args/command_runner.dart';
 import 'package:path/path.dart' as p;
-import 'package:sass_migrator/src/migrators/color.dart';
 import 'package:source_span/source_span.dart';
 import 'package:term_glyph/term_glyph.dart' as glyph;
 
 import 'io.dart';
 import 'migrators/calc_interpolation.dart';
+import 'migrators/color.dart';
 import 'migrators/division.dart';
 import 'migrators/module.dart';
 import 'migrators/namespace.dart';
@@ -42,6 +42,12 @@ class MigratorRunner extends CommandRunner<Map<Uri, String>> {
           abbr: 'd',
           help: 'Migrate dependencies in addition to entrypoints.',
           negatable: false)
+      ..addMultiOption('pkg-importer',
+          abbr: 'p',
+          valueHelp: 'TYPE',
+          allowed: ['node'],
+          help: 'Built-in importer(s) to use for pkg: URLs.',
+          allowedHelp: {'node': 'Load files like Node.js package resolution.'})
       ..addFlag('dry-run',
           abbr: 'n',
           help: 'Show which files would be migrated but make no changes.',

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass_migrator
-version: 2.2.1
+version: 2.3.0
 description: A tool for running migrations on Sass files
 homepage: https://github.com/sass/migrator
 
@@ -17,7 +17,7 @@ dependencies:
   node_interop: ^2.0.2
   node_io: ^2.3.0
   path: ^1.8.0
-  sass_api: ^14.1.0
+  sass_api: ^14.4.0
   source_span: ^1.8.1
   stack_trace: ^1.10.0
   string_scanner: ^1.1.0

test/migrators/module/paths/pkg_node_modules_default.hrx

@@ -0,0 +1,26 @@
+<==> arguments
+--migrate-deps --pkg-importer=node
+
+<==> input/entrypoint.scss
+@import "pkg:module";
+
+a {
+  color: $variable;
+}
+
+<==> input/node_modules/module/styles/index.scss
+$variable: green;
+
+<==> input/node_modules/module/package.json
+{
+  "exports": {
+    "sass": "./styles/index.scss"
+  }
+}
+
+<==> output/entrypoint.scss
+@use "pkg:module";
+
+a {
+  color: module.$variable;
+}

test/migrators/module/paths/pkg_node_modules_subpath.hrx

@@ -0,0 +1,28 @@
+<==> arguments
+--migrate-deps --pkg-importer=node
+
+<==> input/entrypoint.scss
+@import "pkg:module/foo";
+
+a {
+  color: $variable;
+}
+
+<==> input/node_modules/module/styles/test.scss
+$variable: green;
+
+<==> input/node_modules/module/package.json
+{
+  "exports": {
+    "./foo.scss": {
+      "sass": "./styles/test.scss"
+    }
+  }
+}
+
+<==> output/entrypoint.scss
+@use "pkg:module/foo";
+
+a {
+  color: foo.$variable;
+}