Optimize how metadata are copied

packages/console/src/widget.ts

@@ -134,8 +134,14 @@ export class CodeConsole extends Widget {
     });
 
     this._onKernelChanged();
-    this.session.kernelChanged.connect(this._onKernelChanged, this);
-    this.session.statusChanged.connect(this._onKernelStatusChanged, this);
+    this.session.kernelChanged.connect(
+      this._onKernelChanged,
+      this
+    );
+    this.session.statusChanged.connect(
+      this._onKernelStatusChanged,
+      this
+    );
   }
 
   /**
@@ -212,7 +218,10 @@ export class CodeConsole extends Widget {
       this._msgIds.set(msgId, cell);
       this._msgIdCells.set(cell, msgId);
     }
-    cell.disposed.connect(this._onCellDisposed, this);
+    cell.disposed.connect(
+      this._onCellDisposed,
+      this
+    );
     this.update();
   }
 
@@ -224,7 +233,10 @@ export class CodeConsole extends Widget {
       // An old banner just becomes a normal cell now.
       let cell = this._banner;
       this._cells.push(this._banner);
-      cell.disposed.connect(this._onCellDisposed, this);
+      cell.disposed.connect(
+        this._onCellDisposed,
+        this
+      );
     }
     // Create the banner.
     let model = this.modelFactory.createRawCell({});
@@ -340,10 +352,8 @@ export class CodeConsole extends Widget {
   inject(code: string, metadata: JSONObject = {}): Promise<void> {
     let cell = this.createCodeCell();
     cell.model.value.text = code;
-    if (metadata) {
-      for (let key in metadata) {
-        cell.model.metadata.set(key, metadata[key]);
-      }
+    for (let key of Object.keys(metadata)) {
+      cell.model.metadata.set(key, metadata[key]);
     }
     this.addCell(cell);
     return this._execute(cell);
@@ -642,7 +652,10 @@ export class CodeConsole extends Widget {
       this.clear();
       return Promise.resolve(void 0);
     }
-    cell.model.contentChanged.connect(this.update, this);
+    cell.model.contentChanged.connect(
+      this.update,
+      this
+    );
     let onSuccess = (value: KernelMessage.IExecuteReplyMsg) => {
       if (this.isDisposed) {
         return;