Update plugin spec

pkg/analyzer_plugin/lib/plugin/plugin.dart

Index: pkg/analyzer_plugin/lib/plugin/plugin.dart
diff --git a/pkg/analyzer_plugin/lib/plugin/plugin.dart b/pkg/analyzer_plugin/lib/plugin/plugin.dart
index 195e0ca245aa9a99fd37f4d1aabeb4abb857cb8c..3b2310cc03397fd25ecae51f439cba53c427906c 100644
--- a/pkg/analyzer_plugin/lib/plugin/plugin.dart
+++ b/pkg/analyzer_plugin/lib/plugin/plugin.dart
@@ -6,6 +6,7 @@ import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/dart/analysis/byte_store.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart'
     show AnalysisDriverScheduler, PerformanceLog;
+import 'package:analyzer/src/dart/analysis/file_byte_store.dart';
 import 'package:analyzer/src/dart/analysis/file_state.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer_plugin/channel/channel.dart';
@@ -15,6 +16,7 @@ import 'package:analyzer_plugin/protocol/protocol_constants.dart';
 import 'package:analyzer_plugin/src/protocol/protocol_internal.dart';
 import 'package:analyzer_plugin/src/utilities/null_string_sink.dart';
 import 'package:analyzer_plugin/utilities/subscription_manager.dart';
+import 'package:pub_semver/pub_semver.dart';
 
 /**
  * The abstract superclass of any class implementing a plugin for the analysis
@@ -25,6 +27,16 @@ import 'package:analyzer_plugin/utilities/subscription_manager.dart';
  */
 abstract class ServerPlugin {
   /**
+   * A gigabyte.
+   */
+  static const int G = 1024 * 1024 * 1024;
+
+  /**
+   * A megabyte.
+   */
+  static const int M = 1024 * 1024;
+
+  /**
    * The communication channel being used to communicate with the analysis
    * server.
    */
@@ -52,9 +64,11 @@ abstract class ServerPlugin {
       new PerformanceLog(new NullStringSink());
 
   /**
-   * The byte store used by any analysis drivers that are created.
+   * The byte store used by any analysis drivers that are created, or `null` if
+   * the cache location isn't known because the 'plugin.version' request has not
+   * yet been received.
    */
-  final ByteStore byteStore = new MemoryByteStore();
+  ByteStore _byteStore;
 
   /**
    * The file content overlay used by any analysis drivers that are created.
@@ -77,6 +91,28 @@ abstract class ServerPlugin {
   PluginCommunicationChannel get channel => _channel;
 
   /**
+   * Return the user visible information about how to contact the plugin authors
+   * with any problems that are found, or `null` if there is no contact info.
+   */
+  String get contactInfo => null;
+
+  /**
+   * Return a list of glob patterns selecting the files that this plugin is
+   * interested in analyzing.
+   */
+  List<String> get fileGlobsToAnalyze;
+
+  /**
+   * Return the user visible name of this plugin.
+   */
+  String get name;
+
+  /**
+   * Return the version number of this plugin, encoded as a string.
+   */
+  String get version;
+
+  /**
    * Handle the fact that the file with the given [path] has been modified.
    */
   void contentChanged(String path) {
@@ -227,7 +263,25 @@ abstract class ServerPlugin {
    * Handle a 'plugin.versionCheck' request.
    */
   PluginVersionCheckResult handlePluginVersionCheck(
-      Map<String, Object> parameters);
+      Map<String, Object> parameters) {
+    String byteStorePath = validateParameter(parameters,
+        PLUGIN_REQUEST_VERSION_CHECK_BYTESTOREPATH, 'plugin.versionCheck');
+    String versionString = validateParameter(parameters,
+        PLUGIN_REQUEST_VERSION_CHECK_VERSION, 'plugin.versionCheck');
+    Version serverVersion = new Version.parse(versionString);
+    _byteStore =
+        new MemoryCachingByteStore(new FileByteStore(byteStorePath, G), 64 * M);

[scheglov, 2017/02/04 02:01:15]

We might want to avoid using FileByteStore in plugins.
We want to read and write to the same cache.
But FileByteStore also scans the cache directory and evicts older entries.
It is better to have one isolate that does this, in Analysis Server itself.
Let's discuss it on Monday.

[Brian Wilkerson, 2017/02/04 18:06:56]

Ah, I didn't realize it did that much. Could we pull the eviction into a
separate class (something like ByteStoreReaper) so that FileByteStore can be
re-used?

+    return new PluginVersionCheckResult(
+        isCompatibleWith(serverVersion), name, version, fileGlobsToAnalyze,
+        contactInfo: contactInfo);
+  }
+
+  /**
+   * Return `true` if this plugin is compatible with an analysis server that is
+   * using the given version of the plugin API.
+   */
+  bool isCompatibleWith(Version serverVersion) =>
+      serverVersion <= new Version.parse(version);
 
   /**
    * The method that is called when the analysis server closes the communication