[tool] Skip pathified analysis on resolver errors (#4647)

If adding a pathified dependency creates a resolver error, then skip it instead of failing when running pathified analysis. The purpose of pathified analysis it to pre-detect failures that would happen on publishing, and if there's a resolver error that means the publishing even won't affect the package anyway.

See flutter/packages#4483 (comment) for an example case where we need this.

(In theory we could get delayed OOB errors that this will miss�e.g., in the case above if the PR would actually break rfw/example/wasm, then if at some later date `wasm` updated to use a newer `ffi`, eliminating the resolver conflict, then suddenly rfw/example/wasm would pick up the PR and break. That seems *extremely* unlikely, however, so I'm not concerned that this will be a problem in practice. We can revisit if that changes.)

.ci/scripts/analyze_pathified.sh

@@ -10,7 +10,13 @@ set -e
 # This uses --run-on-dirty-packages rather than --packages-for-branch
 # since only the packages changed by 'make-deps-path-based' need to be
 # re-checked.
+# --skip-if-resolving-fails is used to avoid failing if there's a resolution
+# conflict when using path-based dependencies, because that indicates that
+# the failing packages won't pick up the new versions of the changed packages
+# when they are published anyway, so publishing won't cause an out-of-band
+# failure regardless.
 dart ./script/tool/bin/flutter_plugin_tools.dart analyze --run-on-dirty-packages \
+    --skip-if-resolving-fails \
     --log-timing --custom-analysis=script/configs/custom_analysis.yaml
 # Restore the tree to a clean state, to avoid accidental issues if
 # other script steps are added to the enclosing task.

script/tool/lib/src/analyze_command.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:io' as io;
+
 import 'package:file/file.dart';
 import 'package:yaml/yaml.dart';
 
@@ -34,12 +36,18 @@ class AnalyzeCommand extends PackageLoopingCommand {
     argParser.addFlag(_libOnlyFlag,
         help: 'Only analyze the lib/ directory of the main package, not the '
             'entire package.');
+    argParser.addFlag(_skipIfResolvingFailsFlag,
+        help: 'If resolution fails, skip the package. This is only '
+            'intended to be used with pathified analysis, where a resolver '
+            'failure indicates that no out-of-band failure can result anyway.',
+        hide: true);
   }
 
   static const String _customAnalysisFlag = 'custom-analysis';
   static const String _downgradeFlag = 'downgrade';
   static const String _libOnlyFlag = 'lib-only';
   static const String _analysisSdk = 'analysis-sdk';
+  static const String _skipIfResolvingFailsFlag = 'skip-if-resolving-fails';
 
   late String _dartBinaryPath;
 
@@ -134,6 +142,20 @@ class AnalyzeCommand extends PackageLoopingCommand {
               .pubspecFile
               .existsSync()) {
         if (!await _runPubCommand(packageToGet, 'get')) {
+          if (getBoolArg(_skipIfResolvingFailsFlag)) {
+            // Re-run, capturing output, to see if the failure was a resolver
+            // failure. (This is slightly inefficient, but this should be a
+            // very rare case.)
+            const String resolverFailureMessage = 'version solving failed';
+            final io.ProcessResult result = await processRunner.run(
+                flutterCommand, <String>['pub', 'get'],
+                workingDir: packageToGet.directory);
+            if ((result.stderr as String).contains(resolverFailureMessage) ||
+                (result.stdout as String).contains(resolverFailureMessage)) {
+              logWarning('Skipping package due to pub resolution failure.');
+              return PackageResult.skip('Resolution failed.');
+            }
+          }
           return PackageResult.fail(<String>['Unable to get dependencies']);
         }
       }

script/tool/test/analyze_command_test.dart

@@ -315,6 +315,39 @@ void main() {
     });
   });
 
+  test('skips if requested if "pub get" fails in the resolver', () async {
+    final RepositoryPackage plugin = createFakePlugin('foo', packagesDir);
+
+    final FakeProcessInfo failingPubGet = FakeProcessInfo(
+        MockProcess(
+            exitCode: 1,
+            stderr: 'So, because foo depends on both thing_one ^1.0.0 and '
+                'thing_two from path, version solving failed.'),
+        <String>['pub', 'get']);
+    processRunner.mockProcessesForExecutable['flutter'] = <FakeProcessInfo>[
+      failingPubGet,
+      // The command re-runs failures when --skip-if-resolver-fails is passed
+      // to check the output, so provide the same failing outcome.
+      failingPubGet,
+    ];
+
+    final List<String> output = await runCapturingPrint(
+        runner, <String>['analyze', '--skip-if-resolving-fails']);
+
+    expect(
+      output,
+      containsAllInOrder(<Matcher>[
+        contains('Skipping package due to pub resolution failure.'),
+      ]),
+    );
+    expect(
+        processRunner.recordedCalls,
+        orderedEquals(<ProcessCall>[
+          ProcessCall('flutter', const <String>['pub', 'get'], plugin.path),
+          ProcessCall('flutter', const <String>['pub', 'get'], plugin.path),
+        ]));
+  });
+
   test('fails if "pub get" fails', () async {
     createFakePlugin('foo', packagesDir);