Adding 'linux' and 'windows' to TargetPlatform enum
Summary
#Two new values were added to the TargetPlatform
enum
that could require additional cases in switch statements that
switch on a TargetPlatform
and don't include a default:
case.
Context
#Prior to this change, the TargetPlatform
enum only contained four values,
and was defined like this:
enum TargetPlatform {
android,
fuchsia,
iOS,
macOS,
}
A switch
statement only needed to handle these cases,
and desktop applications that wanted to run on Linux or
Windows usually had a test like this in their
main()
method:
// Sets a platform override for desktop to avoid exceptions. See
// https://docs.flutter.dev/desktop#target-platform-override for more info.
void _enablePlatformOverrideForDesktop() {
if (!kIsWeb && (Platform.isWindows || Platform.isLinux)) {
debugDefaultTargetPlatformOverride = TargetPlatform.fuchsia;
}
}
void main() {
_enablePlatformOverrideForDesktop();
runApp(MyApp());
}
Description of change
#The TargetPlatform
enum is now defined as:
enum TargetPlatform {
android,
fuchsia,
iOS,
linux, // new value
macOS,
windows, // new value
}
And the platform test setting
debugDefaultTargetPlatformOverride
in main()
is no longer required on Linux and Windows.
This can cause the Dart analyzer to give the
missing_enum_constant_in_switch
warning for
switch statements that don't include a default
case.
Writing a switch without a default:
case is the
recommended way to handle enums, since the analyzer
can then help you find any cases that aren't handled.
Migration guide
#In order to migrate to the new enum, and avoid the analyzer's
missing_enum_constant_in_switch
error, which looks like:
warning: Missing case clause for 'linux'. (missing_enum_constant_in_switch at [package] path/to/file.dart:111)
or:
warning: Missing case clause for 'windows'. (missing_enum_constant_in_switch at [package] path/to/file.dart:111)
Modify your code as follows:
Code before migration:
void dance(TargetPlatform platform) {
switch (platform) {
case TargetPlatform.android:
// Do Android dance.
break;
case TargetPlatform.fuchsia:
// Do Fuchsia dance.
break;
case TargetPlatform.iOS:
// Do iOS dance.
break;
case TargetPlatform.macOS:
// Do macOS dance.
break;
}
}
Code after migration:
void dance(TargetPlatform platform) {
switch (platform) {
case TargetPlatform.android:
// Do Android dance.
break;
case TargetPlatform.fuchsia:
// Do Fuchsia dance.
break;
case TargetPlatform.iOS:
// Do iOS dance.
break;
case TargetPlatform.linux: // new case
// Do Linux dance.
break;
case TargetPlatform.macOS:
// Do macOS dance.
break;
case TargetPlatform.windows: // new case
// Do Windows dance.
break;
}
}
Having default:
cases in such switch statements isn't
recommended, because then the analyzer can't help you find
all the cases that need to be handled.
Also, any tests like the one referenced above that set the
debugDefaultTargetPlatformOverride
are no longer needed
for Linux and Windows applications.
Timeline
#Landed in version: 1.15.4
In stable release: 1.17
References
#API documentation:
Relevant issues:
Relevant PR:
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