[flutter_tools] cache flutter sdk version to disk (#124558)

Fixes flutter/flutter#112833

Most of the actual changes here are in [packages/flutter_tools/lib/src/version.dart](https://github.com/flutter/flutter/pull/124558/files#diff-092e00109d9e1589fbc7c6de750e29a6ae512b2dd44e85d60028953561201605), while the rest is largely just addressing changes to the constructor of `FlutterVersion` which now has different dependencies.

This change makes `FlutterVersion` an interface with two concrete implementations:

1. `_FlutterVersionGit` which is mostly the previous implementation, and
2. `_FlutterVersionFromFile` which will read a new `.version.json` file from the root of the repo

The [`FlutterVersion` constructor](https://github.com/flutter/flutter/pull/124558/files#diff-092e00109d9e1589fbc7c6de750e29a6ae512b2dd44e85d60028953561201605R70) is now a factory that first checks if `.version.json` exists, and if so returns an instance of `_FlutterVersionFromGit` else it returns the fallback `_FlutterVersionGit` which will end up writing `.version.json` so that we don't need to re-calculate the version on the next invocation.

`.version.json` will be deleted in the bash/batch entrypoints any time we need to rebuild he tool (this will usually be because the user did `flutter upgrade` or `flutter channel`, or manually changed the commit with git).

bin/internal/shared.bat

@@ -128,6 +128,7 @@ GOTO :after_subroutine
 
   :do_snapshot
     IF EXIST "%FLUTTER_ROOT%\version" DEL "%FLUTTER_ROOT%\version"
+    IF EXIST "%FLUTTER_ROOT%\bin\cache\flutter.version.json" DEL "%FLUTTER_ROOT%\bin\cache\flutter.version.json"
     ECHO: > "%cache_dir%\.dartignore"
     ECHO Building flutter tool... 1>&2
     PUSHD "%flutter_tools_dir%"

bin/internal/shared.sh

@@ -123,7 +123,10 @@ function upgrade_flutter () (
   #  * STAMP_PATH is an empty file, or
   #  * Contents of STAMP_PATH is not what we are going to compile, or
   #  * pubspec.yaml last modified after pubspec.lock
-  if [[ ! -f "$SNAPSHOT_PATH" || ! -s "$STAMP_PATH" || "$(cat "$STAMP_PATH")" != "$compilekey" || "$FLUTTER_TOOLS_DIR/pubspec.yaml" -nt "$FLUTTER_TOOLS_DIR/pubspec.lock" ]]; then
+  if [[ ! -f "$SNAPSHOT_PATH" || \
+        ! -s "$STAMP_PATH" || \
+        "$(cat "$STAMP_PATH")" != "$compilekey" || \
+        "$FLUTTER_TOOLS_DIR/pubspec.yaml" -nt "$FLUTTER_TOOLS_DIR/pubspec.lock" ]]; then
     # Waits for the update lock to be acquired. Placing this check inside the
     # conditional allows the majority of flutter/dart installations to bypass
     # the lock entirely, but as a result this required a second verification that
@@ -137,6 +140,7 @@ function upgrade_flutter () (
 
     # Fetch Dart...
     rm -f "$FLUTTER_ROOT/version"
+    rm -f "$FLUTTER_ROOT/bin/cache/flutter.version.json"
     touch "$FLUTTER_ROOT/bin/cache/.dartignore"
     "$FLUTTER_ROOT/bin/internal/update_dart_sdk.sh"
 

packages/flutter_tools/lib/src/commands/doctor.dart

@@ -33,7 +33,6 @@ class DoctorCommand extends FlutterCommand {
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    globals.flutterVersion.fetchTagsAndUpdate();
     if (argResults?.wasParsed('check-for-remote-artifacts') ?? false) {
       final String engineRevision = stringArg('check-for-remote-artifacts')!;
       if (engineRevision.startsWith(RegExp(r'[a-f0-9]{1,40}'))) {

packages/flutter_tools/lib/src/commands/downgrade.dart

@@ -92,7 +92,10 @@ class DowngradeCommand extends FlutterCommand {
     String workingDirectory = Cache.flutterRoot!;
     if (argResults!.wasParsed('working-directory')) {
       workingDirectory = stringArg('working-directory')!;
-      _flutterVersion = FlutterVersion(workingDirectory: workingDirectory);
+      _flutterVersion = FlutterVersion(
+        fs: _fileSystem!,
+        flutterRoot: workingDirectory,
+      );
     }
 
     final String currentChannel = _flutterVersion!.channel;

packages/flutter_tools/lib/src/commands/upgrade.dart

@@ -80,7 +80,7 @@ class UpgradeCommand extends FlutterCommand {
       gitTagVersion: GitTagVersion.determine(globals.processUtils, globals.platform),
       flutterVersion: stringArg('working-directory') == null
         ? globals.flutterVersion
-        : FlutterVersion(workingDirectory: _commandRunner.workingDirectory),
+        : FlutterVersion(flutterRoot: _commandRunner.workingDirectory!, fs: globals.fs),
       verifyOnly: boolArg('verify-only'),
     );
   }
@@ -297,7 +297,11 @@ class UpgradeCommandRunner {
         'for instructions.'
       );
     }
-    return FlutterVersion(workingDirectory: workingDirectory, frameworkRevision: revision);
+    return FlutterVersion.fromRevision(
+      flutterRoot: workingDirectory!,
+      frameworkRevision: revision,
+      fs: globals.fs,
+    );
   }
 
   /// Attempts a hard reset to the given revision.

packages/flutter_tools/lib/src/context_runner.dart

@@ -226,7 +226,10 @@ Future<T> runInContext<T>(
         config: globals.config,
         platform: globals.platform,
       ),
-      FlutterVersion: () => FlutterVersion(),
+      FlutterVersion: () => FlutterVersion(
+        fs: globals.fs,
+        flutterRoot: Cache.flutterRoot!,
+      ),
       FuchsiaArtifacts: () => FuchsiaArtifacts.find(),
       FuchsiaDeviceTools: () => FuchsiaDeviceTools(),
       FuchsiaSdk: () => FuchsiaSdk(),

packages/flutter_tools/lib/src/doctor.dart

@@ -123,7 +123,7 @@ class _DefaultDoctorValidatorsProvider implements DoctorValidatorsProvider {
       FlutterValidator(
         fileSystem: globals.fs,
         platform: globals.platform,
-        flutterVersion: () => globals.flutterVersion,
+        flutterVersion: () => globals.flutterVersion.fetchTagsAndGetVersion(clock: globals.systemClock),
         devToolsVersion: () => globals.cache.devToolsVersion,
         processManager: globals.processManager,
         userMessages: userMessages,

packages/flutter_tools/lib/src/project_validator.dart

@@ -136,7 +136,10 @@ class VariableDumpMachineProjectValidator extends MachineProjectValidator {
     ));
 
     // FlutterVersion
-    final FlutterVersion version = FlutterVersion(workingDirectory: project.directory.absolute.path);
+    final FlutterVersion version = FlutterVersion(
+      flutterRoot: Cache.flutterRoot!,
+      fs: fileSystem,
+    );
     result.add(ProjectValidatorResult(
       name: 'FlutterVersion.frameworkRevision',
       value: _toJsonValue(version.frameworkRevision),

packages/flutter_tools/lib/src/runner/flutter_command_runner.dart

@@ -18,6 +18,7 @@ import '../cache.dart';
 import '../convert.dart';
 import '../globals.dart' as globals;
 import '../tester/flutter_tester.dart';
+import '../version.dart';
 import '../web/web_device.dart';
 
 /// Common flutter command line options.
@@ -318,14 +319,16 @@ class FlutterCommandRunner extends CommandRunner<void> {
 
         if ((topLevelResults[FlutterGlobalOptions.kVersionFlag] as bool?) ?? false) {
           globals.flutterUsage.sendCommand(FlutterGlobalOptions.kVersionFlag);
-          globals.flutterVersion.fetchTagsAndUpdate();
-          String status;
+          final FlutterVersion version = globals.flutterVersion.fetchTagsAndGetVersion(
+            clock: globals.systemClock,
+          );
+          final String status;
           if (machineFlag) {
-            final Map<String, Object> jsonOut = globals.flutterVersion.toJson();
+            final Map<String, Object> jsonOut = version.toJson();
             jsonOut['flutterRoot'] = Cache.flutterRoot!;
             status = const JsonEncoder.withIndent('  ').convert(jsonOut);
           } else {
-            status = globals.flutterVersion.toString();
+            status = version.toString();
           }
           globals.printStatus(status);
           return;