[macOS,iOS] Improve CocoaPods upgrade instructions (flutter#135453)

In our CocoaPods doctor check, if the version of CocoaPods is found to
be too low, rather than emitting a link to the install instructions,
emit a link to the upgrade instructions.

Since this check operates on CocoaPodsStatus, an enum, swtich to using a
case statement and cover all cases.


## Pre-launch Checklist

- [X] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [X] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [X] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [X] I signed the [CLA].
- [ ] I listed at least one issue that this PR fixes in the description
above.
- [X] I updated/added relevant documentation (doc comments with `///`).
- [X] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [X] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[test-exempt]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes
[Discord]: https://github.com/flutter/flutter/wiki/Chat

packages/flutter_tools/lib/src/macos/cocoapods.dart

@@ -48,6 +48,8 @@ const String outOfDatePluginsPodfileConsequence = '''
 
 const String cocoaPodsInstallInstructions = 'see https://guides.cocoapods.org/using/getting-started.html#installation for instructions.';
 
+const String cocoaPodsUpdateInstructions = 'see https://guides.cocoapods.org/using/getting-started.html#updating-cocoapods for instructions.';
+
 const String podfileIosMigrationInstructions = '''
   rm ios/Podfile''';
 

packages/flutter_tools/lib/src/macos/cocoapods_validator.dart

@@ -29,31 +29,28 @@ class CocoaPodsValidator extends DoctorValidator {
       .evaluateCocoaPodsInstallation;
 
     ValidationType status = ValidationType.success;
-    if (cocoaPodsStatus == CocoaPodsStatus.recommended) {
-      messages.add(ValidationMessage(_userMessages.cocoaPodsVersion((await _cocoaPods.cocoaPodsVersionText).toString())));
-    } else {
-      if (cocoaPodsStatus == CocoaPodsStatus.notInstalled) {
+    switch (cocoaPodsStatus) {
+      case CocoaPodsStatus.recommended:
+        messages.add(ValidationMessage(_userMessages.cocoaPodsVersion((await _cocoaPods.cocoaPodsVersionText).toString())));
+      case CocoaPodsStatus.notInstalled:
         status = ValidationType.missing;
         messages.add(ValidationMessage.error(
           _userMessages.cocoaPodsMissing(noCocoaPodsConsequence, cocoaPodsInstallInstructions)));
-
-      } else if (cocoaPodsStatus == CocoaPodsStatus.brokenInstall) {
+      case CocoaPodsStatus.brokenInstall:
         status = ValidationType.missing;
         messages.add(ValidationMessage.error(
           _userMessages.cocoaPodsBrokenInstall(brokenCocoaPodsConsequence, cocoaPodsInstallInstructions)));
-
-      } else if (cocoaPodsStatus == CocoaPodsStatus.unknownVersion) {
+      case CocoaPodsStatus.unknownVersion:
         status = ValidationType.partial;
         messages.add(ValidationMessage.hint(
           _userMessages.cocoaPodsUnknownVersion(unknownCocoaPodsConsequence, cocoaPodsInstallInstructions)));
-      } else {
+      case CocoaPodsStatus.belowMinimumVersion:
+      case CocoaPodsStatus.belowRecommendedVersion:
         status = ValidationType.partial;
         final String currentVersionText = (await _cocoaPods.cocoaPodsVersionText).toString();
         messages.add(ValidationMessage.hint(
-          _userMessages.cocoaPodsOutdated(currentVersionText, cocoaPodsRecommendedVersion.toString(), noCocoaPodsConsequence, cocoaPodsInstallInstructions)));
-      }
+          _userMessages.cocoaPodsOutdated(currentVersionText, cocoaPodsRecommendedVersion.toString(), noCocoaPodsConsequence, cocoaPodsUpdateInstructions)));
     }
-
     return ValidationResult(status, messages);
   }
 }

packages/flutter_tools/test/general.shard/macos/cocoapods_validator_test.dart

@@ -41,6 +41,7 @@ void main() {
       expect(message.type, ValidationMessageType.hint);
       expect(message.message, contains('CocoaPods $currentVersion out of date'));
       expect(message.message, contains('(1.11.0 is recommended)'));
+      expect(message.message, contains('getting-started.html#updating-cocoapods'));
     });
   });
 }