Add package_root for fuchsia_tools (#56077)

packages/flutter_tools/BUILD.gn

@@ -57,6 +57,7 @@ dart_library("flutter_tools") {
 
 dart_tool("fuchsia_builder") {
   main_dart = "bin/fuchsia_builder.dart"
+  package_root = "fuchsia_entrypoint_shim/fuchsia_builder"
 
   disable_analysis = true
 
@@ -67,6 +68,7 @@ dart_tool("fuchsia_builder") {
 
 dart_tool("fuchsia_asset_builder") {
   main_dart = "bin/fuchsia_asset_builder.dart"
+  package_root = "fuchsia_entrypoint_shim/fuchsia_asset_builder"
 
   disable_analysis = true
 
@@ -153,6 +155,7 @@ dart_tool("fuchsia_asset_builder") {
 
 dart_tool("fuchsia_tester") {
   main_dart = "bin/fuchsia_tester.dart"
+  package_root = "fuchsia_entrypoint_shim/tester"
 
   disable_analysis = true
 
@@ -248,6 +251,7 @@ dart_tool("fuchsia_tester") {
 dart_tool("fuchsia_attach") {
   package_name = "fuchsia_attach"
   main_dart = "bin/fuchsia_attach.dart"
+  package_root = "fuchsia_entrypoint_shim/attach"
 
   # Can be left empty as analysis is disabled.
   sources = []

packages/flutter_tools/fuchsia_entrypoint_shim/README.md

+This directory serves as a placeholder directory for the package roots of
+various fuchsia tools which use the flutter_tools library.
+
+This is required to provide a workaround for the fuchsia build system.
+When this directory is not present the various tools specified in the
+`dart_tool` directives in the flutter_tools/BUILD.gn file will end up
+having the same package root entry written in the .packages file. This
+causes the build to fail because the dart compiler has a requirement that
+libraries must have a unique package uri. By specifying a package root which
+is a subdirectory of this directory for these tools we avoid having the build
+system create duplicate package roots for the generated libraries for these
+tools.
+
+Note that we cannot move the location of the main files for these tools because
+the paths are hard coded in the fuchsia tree.
+
+
+Tracking Bugs:
+- fxbug.dev/51373 (move flutter_tools/BUILD.gn to fuchsia repo)
+- fxbug.dev/51375 (do not refence fuchsia_tester.dart directly)
+- fxbug.dev/51375 (remove the fuchsia_entrypoint_shim directory)

packages/flutter_tools/fuchsia_entrypoint_shim/fuchsia_asset_builder/pubspec.yaml

+name: flutter_asset_builder
+description: Tools for building Flutter applications
+homepage: https://flutter.dev
+author: Flutter Authors <flutter-dev@googlegroups.com>
+
+environment:
+  # The pub client defaults to an <2.0.0 sdk constraint which we need to explicitly overwrite.
+  sdk: ">=2.7.0 <3.0.0"
+
+dartdoc:
+  # Exclude this package from the hosted API docs.
+  nodoc: true
+
+# PUBSPEC CHECKSUM: 0000

packages/flutter_tools/fuchsia_entrypoint_shim/fuchsia_attach/pubspec.yaml

+name: flutter_attach
+description: Tools for building Flutter applications
+homepage: https://flutter.dev
+author: Flutter Authors <flutter-dev@googlegroups.com>
+
+environment:
+  # The pub client defaults to an <2.0.0 sdk constraint which we need to explicitly overwrite.
+  sdk: ">=2.7.0 <3.0.0"
+
+dartdoc:
+  # Exclude this package from the hosted API docs.
+  nodoc: true
+
+# PUBSPEC CHECKSUM: 0000

packages/flutter_tools/fuchsia_entrypoint_shim/fuchsia_builder/pubspec.yaml

+name: flutter_builder
+description: Tools for building Flutter applications
+homepage: https://flutter.dev
+author: Flutter Authors <flutter-dev@googlegroups.com>
+
+environment:
+  # The pub client defaults to an <2.0.0 sdk constraint which we need to explicitly overwrite.
+  sdk: ">=2.7.0 <3.0.0"
+
+dartdoc:
+  # Exclude this package from the hosted API docs.
+  nodoc: true
+
+# PUBSPEC CHECKSUM: 0000

packages/flutter_tools/fuchsia_entrypoint_shim/fuchsia_tester/pubspec.yaml

+name: flutter_tester
+description: Tools for building Flutter applications
+homepage: https://flutter.dev
+author: Flutter Authors <flutter-dev@googlegroups.com>
+
+environment:
+  # The pub client defaults to an <2.0.0 sdk constraint which we need to explicitly overwrite.
+  sdk: ">=2.7.0 <3.0.0"
+
+dartdoc:
+  # Exclude this package from the hosted API docs.
+  nodoc: true
+
+# PUBSPEC CHECKSUM: 0000