fix(select): wrong panel width if element is hidden initially

Fixes the select not having a proper width if it became visible after it was initialized.

Fixes #3639.

Author: crisbeto

src/lib/select/select.spec.ts

@@ -43,7 +43,8 @@ describe('MdSelect', () => {
         ThrowsErrorOnInit,
         BasicSelectOnPush,
         BasicSelectOnPushPreselected,
-        SelectWithPlainTabindex
+        SelectWithPlainTabindex,
+        BasicSelectInitiallyHidden
       ],
       providers: [
         {provide: OverlayContainer, useFactory: () => {
@@ -155,6 +156,25 @@ describe('MdSelect', () => {
       });
     }));
 
+    it('should set the width of the overlay if the element was hidden initially', async(() => {
+      let initiallyHidden = TestBed.createComponent(BasicSelectInitiallyHidden);
+
+      initiallyHidden.detectChanges();
+      trigger = initiallyHidden.debugElement.query(By.css('.mat-select-trigger')).nativeElement;
+      trigger.style.width = '200px';
+
+      initiallyHidden.componentInstance.isVisible = true;
+      initiallyHidden.detectChanges();
+
+      initiallyHidden.whenStable().then(() => {
+        trigger.click();
+        initiallyHidden.detectChanges();
+
+        const pane = overlayContainerElement.querySelector('.cdk-overlay-pane') as HTMLElement;
+        expect(pane.style.minWidth).toBe('200px');
+      });
+    }));
+
     it('should not attempt to open a select that does not have any options', () => {
       fixture.componentInstance.foods = [];
       fixture.detectChanges();
@@ -1893,6 +1913,18 @@ class MultiSelect {
 })
 class SelectWithPlainTabindex { }
 
+@Component({
+  selector: 'basic-select-initially-hidden',
+  template: `
+    <md-select [style.display]="isVisible ? 'block' : 'none'">
+      <md-option value="value">There are no other options</md-option>
+    </md-select>
+  `
+})
+class BasicSelectInitiallyHidden {
+  isVisible = false;
+}
+
 
 class FakeViewportRuler {
   getViewportRect() {

src/lib/select/select.ts

@@ -236,7 +236,7 @@ export class MdSelect implements AfterContentInit, ControlValueAccessor, OnDestr
     this._placeholder = value;
 
     // Must wait to record the trigger width to ensure placeholder width is included.
-    Promise.resolve(null).then(() => this._triggerWidth = this._getWidth());
+    Promise.resolve(null).then(() => this._setTriggerWidth());
   }
 
   /** Whether the component is disabled. */
@@ -341,6 +341,11 @@ export class MdSelect implements AfterContentInit, ControlValueAccessor, OnDestr
     if (this.disabled || !this.options.length) {
       return;
     }
+
+    if (!this._triggerWidth) {
+      this._setTriggerWidth();
+    }
+
     this._calculateOverlayPosition();
     this._placeholderState = this._floatPlaceholderState();
     this._panelOpen = true;
@@ -423,11 +428,12 @@ export class MdSelect implements AfterContentInit, ControlValueAccessor, OnDestr
     return this._dir ? this._dir.value === 'rtl' : false;
   }
 
-  /** The width of the trigger element. This is necessary to match
+  /**
+   * Sets the width of the trigger element. This is necessary to match
    * the overlay width to the trigger width.
    */
-  _getWidth(): number {
-    return this._getTriggerRect().width;
+  private _setTriggerWidth(): void {
+    this._triggerWidth = this._getTriggerRect().width;
   }
 
   /** Ensures the panel opens if activated by the keyboard. */