add new options to cli

Author: christopherfujino

tools/const_finder/bin/main.dart

@@ -55,20 +55,46 @@ void main(List<String> args) {
     ..addFlag('help',
         abbr: 'h',
         negatable: false,
-        help: 'Print usage and exit');
+        help: 'Print usage and exit')
+    ..addMultiOption('ignored-class-name',
+      help: 'The name of a class whose containing constant instances that '
+            'should not be retained. This is useful in situations--such as '
+            'the web--where unused constants are not tree shaken from dill '
+            'files.\n\nNote: each provided class name must pair with an '
+            'invocation of "--ignored-class-library-uri" and appear in the '
+            'same order.',
+        valueHelp: 'Icons')
+    ..addMultiOption('ignored-class-library-uri',
+        help: 'The package: URI of a class to ignore.\n\nNote: each provided '
+              'class name must pair with an invocation of '
+              '"--ignored-class-name" and appear in the same order.',
+        valueHelp: 'package:flutter/src/material/icons.dart');
 
   final ArgResults argResults = parser.parse(args);
-  T getArg<T>(String name) => argResults[name] as T;
+  T getArg<T>(String name) {
+    try {
+      return argResults[name] as T;
+    } catch (err) {
+      stderr.writeln('Parsing error trying to parse the argument "$name"');
+      rethrow;
+    }
+  }
 
   if (getArg<bool>('help')) {
     stdout.writeln(parser.usage);
     exit(0);
   }
 
+  final List<List<String>> ignoredClasses = _pairIgnoredClassNamesAndUris(
+    getArg<Object?>('ignored-class-name'),
+    getArg<Object?>('ignored-class-library-uri'),
+  );
+
   final ConstFinder finder = ConstFinder(
     kernelFilePath: getArg<String>('kernel-file'),
     classLibraryUri: getArg<String>('class-library-uri'),
     className: getArg<String>('class-name'),
+    ignoredClasses: ignoredClasses,
   );
 
   final JsonEncoder encoder = getArg<bool>('pretty')
@@ -77,3 +103,38 @@ void main(List<String> args) {
 
   stdout.writeln(encoder.convert(finder.findInstances()));
 }
+
+List<List<String>> _pairIgnoredClassNamesAndUris(Object? names, Object? uris) {
+  // If the user provided neither option then we will not ignore any classes.
+  if (names == null && uris == null) {
+    return const <List<String>>[];
+  }
+  // If the user provided one of the options but not the other, than this is a
+  // error!
+  if (names == null || uris == null) {
+    stderr.writeln(
+      'To ignore specific classes, both "--ignored-class-name" AND '
+      '"--ignored-class-library-uri" must be provided in order to uniquely '
+      'identify the class.',
+    );
+    exit(1);
+  }
+
+  names = names as List<String>;
+  uris = uris as List<String>;
+  final List<List<String>> pairs = <List<String>>[];
+
+  if (names.length != uris.length) {
+    stderr.writeln(
+      '"--ignored-class-name" was provided ${names.length} time(s) but '
+      '"--ignored-class-library-uri" was provided ${uris.length} time(s). '
+      'Each ignored class name must be paired with exactly one ignored class '
+      'library uri, provided in the same order.',
+    );
+    exit(1);
+  }
+  for (int i = 0; i < names.length; i++) {
+    pairs.add(<String>[uris[i], names[i]]);
+  }
+  return pairs;
+}

tools/const_finder/lib/const_finder.dart

@@ -99,7 +99,7 @@ class _ConstVisitor extends RecursiveVisitor<void> {
   @override
   void visitInstanceConstantReference(InstanceConstant node) {
     super.visitInstanceConstantReference(node);
-    if (!_matches(node.classNode)) {
+    if (!_matches(node.classNode) || inIgnoredClass) {
       return;
     }
 
@@ -111,20 +111,12 @@ class _ConstVisitor extends RecursiveVisitor<void> {
       final PrimitiveConstant<dynamic> value = kvp.value as PrimitiveConstant<dynamic>;
       instance[kvp.key.asField.name.text] = value.value;
     }
-    if (!inIgnoredClass) {
-      if (_visitedInstances.add(instance.toString())) {
-        if (instance['stringValue'] == 'unused1') {
-          throw 'whoops';
-        }
-        constantInstances.add(instance);
-      }
+    if (_visitedInstances.add(instance.toString())) {
+      constantInstances.add(instance);
     }
   }
 }
 
-/// For debugging.
-Library? lastLibrary;
-
 /// A kernel AST visitor that finds const references.
 class ConstFinder {
   /// Creates a new ConstFinder class.  All arguments are required and must not
@@ -149,7 +141,6 @@ class ConstFinder {
   Map<String, dynamic> findInstances() {
     _visitor._visitedInstances.clear();
     for (final Library library in loadComponentFromBinary(_visitor.kernelFilePath).libraries) {
-      lastLibrary = library;
       library.visitChildren(_visitor);
     }
     return <String, dynamic>{