Use tools/VERSION in generate_package_config to resolve repo

Change-Id: Icd47684008e6e8054eef273a0ede624ca006f7c0
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/420702
Reviewed-by: Alexander Thomas <[email protected]>
Reviewed-by: Ivan Inozemtsev <[email protected]>
Commit-Queue: Sigurd Meldgaard <[email protected]>

Author: sigurdm

tools/generate_package_config.dart

@@ -57,7 +57,10 @@ $overrides
     Platform.resolvedExecutable,
     ['pub', 'get'],
     workingDirectory: repoRoot.toFilePath(),
-    environment: {}, // Prevent overriding, e.g., PUB_CACHE
+    // Solve pretending we are running [currentSDKVersion].
+    environment: {
+      '_PUB_TEST_SDK_VERSION': currentSDKVersion()
+    }, // Prevent overriding, e.g., PUB_CACHE
   );
   if (result.exitCode != 0) {
     print('`pub get` failed');
@@ -95,3 +98,16 @@ $overrides
     }
   }
 }
+
+String currentSDKVersion() {
+  final versionContents =
+      File.fromUri(repoRoot.resolve('tools/VERSION')).readAsStringSync();
+  final lines = versionContents
+      .split('\n')
+      .where((line) => !line.startsWith('#') && line.isNotEmpty);
+  final versionParts = Map.fromEntries(lines.map((line) {
+    final parts = line.split(' ');
+    return MapEntry(parts[0], parts[1]);
+  }));
+  return '${versionParts['MAJOR']}.${versionParts['MINOR']}.${versionParts['PATCH']}';
+}