Update usages of fromEnvironment to handle breaking change #40678

[eernstg]

SDK issue 40678 is concerned with a breaking change which will be performed in the Dart language and core libraries: The constant constructors int.fromEnvironment and String.fromEnvironment will have default values 0 and "", respectively, for the parameter named defaultValue.

This means that the following usages in protobuf will have a new semantics (and presumably will not work as intended):

./third_party/pkg/protobuf/query_benchmark/bin/encode_json.dart:  String path = const String.fromEnvironment('testfile') ?? 'testdata/500.pb';
./third_party/pkg/protobuf/query_benchmark/bin/decode.dart:  String path = const String.fromEnvironment('testfile') ?? 'testdata/500.pb';
./third_party/pkg/protobuf/query_benchmark/bin/set_nested_value.dart:  String path = const String.fromEnvironment('testfile') ?? 'testdata/500.pb';
./third_party/pkg/protobuf/query_benchmark/bin/encode.dart:  String path = const String.fromEnvironment('testfile') ?? 'testdata/500.pb';
./third_party/pkg/protobuf/query_benchmark/bin/decode_json.dart:  String path = const String.fromEnvironment('testfile') ?? 'testdata/500.pb';

The expressions should be changed as follows in order to work:

// Current form
String path = const String.fromEnvironment('testfile') ?? 'testdata/500.pb';

// New form that will work also after the breaking change has occurred.
String path = const bool.hasEnvironment('testfile')
    ? const String.fromEnvironment('testfile')
    : 'testdata/500.pb';

The constructor bool.hasEnvironment has been added to Dart as of dart-lang/sdk@4aba581. Until that commit is available, it is possible to replace const bool.hasEnvironment('testfile') by (const String.fromEnvironment('testfile', defaultValue: 'a') == const String.fromEnvironment('testfile', defaultValue: 'b')).

[osa1]

It seems like this was fixed by f611f23. I checked uses of fromEnvironment methods. We don't use int.fromEnvironment, and for String.fromEnvironment we always specify the default values:

query_benchmark/bin/decode_json.dart:11:      const String.fromEnvironment('testfile', defaultValue: 'testdata/500.pb');
query_benchmark/bin/decode.dart:11:      const String.fromEnvironment('testfile', defaultValue: 'testdata/500.pb');
query_benchmark/bin/set_nested_value.dart:14:      const String.fromEnvironment('testfile', defaultValue: 'testdata/500.pb');
query_benchmark/bin/encode_json.dart:11:      const String.fromEnvironment('testfile', defaultValue: 'testdata/500.pb');
query_benchmark/bin/encode.dart:11:      const String.fromEnvironment('testfile', defaultValue: 'testdata/500.pb');