[flutter_tool] remove ability to disable Fingerprinter with...

[flutter_tool] remove ability to disable Fingerprinter with DISABLE_FLUTTER_BUILD_CACHE env variable (#46913)

packages/flutter_tools/lib/src/base/fingerprint.dart

@@ -10,18 +10,10 @@ import '../convert.dart' show json;
 import '../globals.dart';
 import '../version.dart';
 import 'file_system.dart';
-import 'platform.dart';
 import 'utils.dart';
 
 typedef FingerprintPathFilter = bool Function(String path);
 
-/// Whether to completely disable build caching.
-///
-/// This is done by always returning false from fingerprinter invocations. This
-/// is safe to do generally, because fingerprinting is only a performance
-/// improvement.
-bool get _disableBuildCache => platform.environment['DISABLE_FLUTTER_BUILD_CACHE']?.toLowerCase() == 'true';
-
 /// A tool that can be used to compute, compare, and write [Fingerprint]s for a
 /// set of input files and associated build settings.
 ///
@@ -57,9 +49,6 @@ class Fingerprinter {
   }
 
   bool doesFingerprintMatch() {
-    if (_disableBuildCache) {
-      return false;
-    }
     try {
       final File fingerprintFile = fs.file(fingerprintPath);
       if (!fingerprintFile.existsSync()) {

packages/flutter_tools/test/general.shard/base/fingerprint_test.dart

@@ -195,48 +195,6 @@ void main() {
       expect(fingerprinter.doesFingerprintMatch(), isTrue);
     }, overrides: contextOverrides);
 
-    final Platform mockPlatformDisabledCache = MockPlatform();
-    mockPlatformDisabledCache.environment['DISABLE_FLUTTER_BUILD_CACHE']  = 'true';
-    testUsingContext('can be disabled with an environment variable', () {
-      fs.file('a.dart').createSync();
-      fs.file('b.dart').createSync();
-
-      final Fingerprinter fingerprinter = Fingerprinter(
-        fingerprintPath: 'out.fingerprint',
-        paths: <String>['a.dart', 'b.dart'],
-        properties: <String, String>{
-          'bar': 'baz',
-          'wobble': 'womble',
-        },
-      );
-      fingerprinter.writeFingerprint();
-      expect(fingerprinter.doesFingerprintMatch(), isFalse);
-    }, overrides: <Type, Generator>{
-      Platform: () => mockPlatformDisabledCache,
-      ...contextOverrides,
-    });
-
-    final Platform mockPlatformEnabledCache = MockPlatform();
-    mockPlatformEnabledCache.environment['DISABLE_FLUTTER_BUILD_CACHE']  = 'false';
-    testUsingContext('can be not-disabled with an environment variable', () {
-      fs.file('a.dart').createSync();
-      fs.file('b.dart').createSync();
-
-      final Fingerprinter fingerprinter = Fingerprinter(
-        fingerprintPath: 'out.fingerprint',
-        paths: <String>['a.dart', 'b.dart'],
-        properties: <String, String>{
-          'bar': 'baz',
-          'wobble': 'womble',
-        },
-      );
-      fingerprinter.writeFingerprint();
-      expect(fingerprinter.doesFingerprintMatch(), isTrue);
-    }, overrides: <Type, Generator>{
-      Platform: () => mockPlatformEnabledCache,
-      ...contextOverrides,
-    });
-
     testUsingContext('fails to write fingerprint if inputs are missing', () {
       final Fingerprinter fingerprinter = Fingerprinter(
         fingerprintPath: 'out.fingerprint',