build: add rule to enforce static queries (#15963)

Adds a simplified tslint rule to enforce that we've explicitly set the `static` flag on relevant queries. We don't need the more advanced functionality from the one in angular/angular, because we don't have to figure out which value is correct, only that it is set.

Author: crisbeto

src/cdk-experimental/popover-edit/popover-edit.spec.ts

@@ -54,7 +54,7 @@ interface PeriodicElement {
 }
 
 abstract class BaseTestComponent {
-  @ViewChild('table') table: ElementRef;
+  @ViewChild('table', {static: false}) table: ElementRef;
 
   preservedValues = new Map<number, PeriodicElement>();
 

src/material-experimental/mdc-checkbox/checkbox.spec.ts

@@ -1050,7 +1050,7 @@ class CheckboxWithTabIndex {
     <mat-checkbox></mat-checkbox>`,
 })
 class CheckboxUsingViewChild {
-  @ViewChild(MatCheckbox) checkbox: MatCheckbox;
+  @ViewChild(MatCheckbox, {static: false}) checkbox: MatCheckbox;
 
   set isDisabled(value: boolean) {
     this.checkbox.disabled = value;

src/material-experimental/popover-edit/popover-edit.spec.ts

@@ -58,7 +58,7 @@ interface PeriodicElement {
 }
 
 abstract class BaseTestComponent {
-  @ViewChild('table') table: ElementRef;
+  @ViewChild('table', {static: false}) table: ElementRef;
 
   preservedValues = new Map<number, PeriodicElement>();
 

tools/tslint-rules/staticQueryRule.ts

@@ -0,0 +1,38 @@
+import * as ts from 'typescript';
+import * as Lint from 'tslint';
+
+/**
+ * Rule which enforces that all queries are explicitly marked as static or non-static.
+ */
+export class Rule extends Lint.Rules.AbstractRule {
+  apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+    return this.applyWithWalker(new Walker(sourceFile, this.getOptions()));
+  }
+}
+
+class Walker extends Lint.RuleWalker {
+  visitPropertyDeclaration(node: ts.PropertyDeclaration) {
+    const childQueryDecorator = node.decorators && node.decorators.find(decorator => {
+      const expression = (decorator.expression as ts.CallExpression);
+      const name = expression && expression.expression.getText();
+      return name === 'ViewChild' || name === 'ContentChild';
+    });
+
+    if (childQueryDecorator) {
+      const options = (childQueryDecorator.expression as ts.CallExpression).arguments[1];
+
+      if (!options || !ts.isObjectLiteralExpression(options) ||
+          !this._getObjectProperty(options, 'static')) {
+        this.addFailureAtNode(childQueryDecorator,
+                              'Queries have to explicitly set the `static` option.');
+      }
+    }
+
+    super.visitPropertyDeclaration(node);
+  }
+
+  /** Gets the node of an object property by name. */
+  private _getObjectProperty(node: ts.ObjectLiteralExpression, name: string) {
+    return node.properties.find(property => (property.name as ts.Identifier).getText() === name);
+  }
+}

tslint.json

@@ -102,6 +102,7 @@
     "ng-on-changes-property-access": true,
     "rxjs-imports": true,
     "require-breaking-change-version": true,
+    "static-query": true,
     "no-host-decorator-in-concrete": [
       true,
       "HostBinding",