analyzer: Move the API tool so that it can generate API for other packages

Also, add some scripts to generate the analyzer_testing API, and checkin
the api.txt file for analyzer_testing.

In order to avoid a private analyzer import, I add `isExperimental` and
`hasExperimental` support for `@experimental` annotation, and switch
to using public APIs in `_dumpElement`.

Change-Id: I44319270d4e6083b80973b45933268c472876232
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/426282
Commit-Queue: Samuel Rawlins <[email protected]>
Reviewed-by: Paul Berry <[email protected]>

Author: srawlins

pkg/analyzer/api.txt

@@ -3087,6 +3087,7 @@ package:analyzer/dart/element/element.dart:
     isDeprecated (getter: bool)
     isDoNotStore (getter: bool)
     isDoNotSubmit (getter: bool)
+    isExperimental (getter: bool)
     isFactory (getter: bool)
     isImmutable (getter: bool)
     isInternal (getter: bool)
@@ -3555,6 +3556,7 @@ package:analyzer/dart/element/element.dart:
     hasDeprecated (getter: bool)
     hasDoNotStore (getter: bool)
     hasDoNotSubmit (getter: bool)
+    hasExperimental (getter: bool)
     hasFactory (getter: bool)
     hasImmutable (getter: bool)
     hasInternal (getter: bool)

pkg/analyzer/lib/dart/element/element.dart

@@ -733,6 +733,9 @@ abstract class ElementAnnotation implements ConstantEvaluationTarget {
   /// Whether the annotation marks the associated member as not to be used.
   bool get isDoNotSubmit;
 
+  /// Whether the annotation marks the associated element as experimental.
+  bool get isExperimental;
+
   /// Whether the annotation marks the associated member as a factory.
   bool get isFactory;
 
@@ -2637,6 +2640,9 @@ abstract class Metadata {
   /// Whether the receiver has an annotation of the form `@doNotSubmit`.
   bool get hasDoNotSubmit;
 
+  /// Whether the receiver has an annotation of the form `@experimental`.
+  bool get hasExperimental;
+
   /// Whether the receiver has an annotation of the form `@factory`.
   bool get hasFactory;
 

pkg/analyzer/lib/src/dart/element/element.dart

@@ -1511,6 +1511,9 @@ class ElementAnnotationImpl implements ElementAnnotation {
   /// used (for ephemeral testing and debugging only).
   static const String _doNotSubmitVariableName = 'doNotSubmit';
 
+  /// The name of the top-level variable used to mark a declaration as experimental.
+  static const String _experimentalVariableName = 'experimental';
+
   /// The name of the top-level variable used to mark a method as being a
   /// factory.
   static const String _factoryVariableName = 'factory';
@@ -1723,6 +1726,9 @@ class ElementAnnotationImpl implements ElementAnnotation {
   @override
   bool get isDoNotSubmit => _isPackageMetaGetter(_doNotSubmitVariableName);
 
+  @override
+  bool get isExperimental => _isPackageMetaGetter(_experimentalVariableName);
+
   @override
   bool get isFactory => _isPackageMetaGetter(_factoryVariableName);
 
@@ -6924,6 +6930,18 @@ final class MetadataImpl implements Metadata {
     return false;
   }
 
+  @override
+  bool get hasExperimental {
+    var annotations = this.annotations;
+    for (var i = 0; i < annotations.length; i++) {
+      var annotation = annotations[i];
+      if (annotation.isExperimental) {
+        return true;
+      }
+    }
+    return false;
+  }
+
   @override
   bool get hasFactory {
     var annotations = this.annotations;