update cached R Markdown package state after install; fixes #1801

After successfully installing the R Markdown package on demand, most of
the session info still indicates that the package doesn't exist. This
change updates the session info in place when a recent version of the
package is successfully installed so that commands like Knit with
Parameters can be used in the very first RStudio session.

src/gwt/src/org/rstudio/core/client/command/AppCommand.java

@@ -193,6 +193,15 @@ public void setVisible(boolean visible)
          handlers_.fireEvent(new VisibleChangedEvent(this));
       }
    }
+
+   /**
+    * Restores a command which was formerly removed. The command must still be made
+    * visible and enabled in order to work.
+    */
+   public void restore()
+   {
+      removed_ = false;
+   }
 
    public boolean isCheckable()
    {

src/gwt/src/org/rstudio/studio/client/common/dependencies/DependencyManager.java

@@ -36,6 +36,8 @@
 import org.rstudio.studio.client.common.dependencies.model.DependencyServerOperations;
 import org.rstudio.studio.client.server.ServerError;
 import org.rstudio.studio.client.server.ServerRequestCallback;
+import org.rstudio.studio.client.workbench.commands.Commands;
+import org.rstudio.studio.client.workbench.model.Session;
 import org.rstudio.studio.client.workbench.views.packages.events.PackageStateChangedEvent;
 import org.rstudio.studio.client.workbench.views.packages.events.PackageStateChangedHandler;
 import org.rstudio.studio.client.workbench.views.vcs.common.ConsoleProgressDialog;
@@ -82,12 +84,16 @@ class DependencyRequest
    @Inject
    public DependencyManager(GlobalDisplay globalDisplay,
                             DependencyServerOperations server,
-                            EventBus eventBus)
+                            EventBus eventBus,
+                            Session session,
+                            Commands commands)
    {
       globalDisplay_ = globalDisplay;
       server_ = server;
       satisfied_ = new ArrayList<Dependency>();
       requestQueue_ = new LinkedList<DependencyRequest>();
+      session_ = session;
+      commands_ = commands;
 
       eventBus.addHandler(InstallShinyEvent.TYPE, this);
       eventBus.addHandler(PackageStateChangedEvent.TYPE, this);
@@ -177,19 +183,13 @@ public void withRMarkdown(String userAction, final Command command)
    public void withRMarkdown(String progressCaption, String userAction, 
          final Command command)
    {
-     withDependencies(
+     withRMarkdown(
         progressCaption,
         userAction, 
-        rmarkdownDependenciesArray(), 
-        true, // we want to update to the embedded version if needed
-        new CommandWithArg<Boolean>()
+        succeeded ->
         {
-         @Override
-         public void execute(Boolean succeeded)
-         {
-            if (succeeded)
-               command.execute();
-         }
+           if (succeeded)
+              command.execute();
         }
      );
    }
@@ -201,8 +201,22 @@ public void withRMarkdown(String progressCaption, String userAction,
         progressCaption,
         userAction, 
         rmarkdownDependenciesArray(), 
-        true, 
-        command);
+        true, // we want to update to the embedded version if needed
+        succeeded -> 
+        {
+           if (succeeded)
+           {
+              // if we successfully installed the latest R Markdown version,
+              // update the session cache of package information.
+              session_.getSessionInfo().setKnitParamsAvailable(true);
+              session_.getSessionInfo().setRMarkdownPackageAvailable(true);
+              session_.getSessionInfo().setKnitWorkingDirAvailable(true);
+
+              // restore removed commands
+              commands_.knitWithParameters().restore();
+           }
+           command.execute(succeeded);
+        });
    }
 
    public static List<Dependency> rmarkdownDependencies()
@@ -1059,4 +1073,6 @@ private void updateSatisfied(JsArray<Dependency> all,
    private final GlobalDisplay globalDisplay_;
    private final DependencyServerOperations server_;
    private final ArrayList<Dependency> satisfied_;
+   private final Session session_;
+   private final Commands commands_;
 }

src/gwt/src/org/rstudio/studio/client/workbench/model/SessionInfo.java

@@ -415,13 +415,25 @@ public final native boolean getRMarkdownPackageAvailable() /*-{
       return this.rmarkdown_available;
    }-*/;
 
+   public final native void setRMarkdownPackageAvailable(boolean available) /*-{
+      this.rmarkdown_available = available;
+   }-*/;
+
    public final native boolean getKnitParamsAvailable()  /*-{
       return this.knit_params_available;
    }-*/;
 
+   public final native void setKnitParamsAvailable(boolean available) /*-{
+      this.knit_params_available = available;
+   }-*/;
+
    public final native boolean getKnitWorkingDirAvailable() /*-{
       return this.knit_working_dir_available;
    }-*/;
+
+   public final native void setKnitWorkingDirAvailable(boolean available) /*-{
+      this.knit_working_dir_available = available;
+   }-*/;
 
    public final native boolean getClangAvailable() /*-{
       return this.clang_available;

src/gwt/src/org/rstudio/studio/client/workbench/views/source/editors/text/TextEditingTargetRMarkdownHelper.java

@@ -417,7 +417,6 @@ public boolean verifyPrerequisites(String feature,
          else if (fileType.requiresKnit() && 
                   !session_.getSessionInfo().getRMarkdownPackageAvailable())
          {
-
             showKnitrPreviewWarning(display, feature, "1.2");
             return false;
          }