refactor(ivy): let `strictTemplates` imply `fullTemplateTypeCheck` (#34195)

Previously, it was required that both `fullTemplateTypeCheck` and
`strictTemplates` had to be enabled for strict mode to be enabled. This
is strange, as `strictTemplates` implies `fullTemplateTypeCheck`. This
commit makes setting the `fullTemplateTypeCheck` flag optional so that
strict mode can be enabled by just setting `strictTemplates`.

PR Close #34195

aio/content/guide/template-typecheck.md

@@ -46,7 +46,7 @@ The following still have type `any`.
 ### Strict mode
 
 Angular version 9 maintains the behavior of the `fullTemplateTypeCheck` flag, and introduces a third "strict mode".
-Strict mode is accessed by setting both `fullTemplateTypeCheck` and the `strictTemplates` flag to `true`.
+Strict mode is a superset of full mode, and is accessed by setting the `strictTemplates` flag to true. This flag supersedes the `fullTemplateTypeCheck` flag.
 In strict mode, Angular version 9 adds checks that go beyond the version 8 type-checker.
 Note that strict mode is only available if using Ivy.
 

packages/compiler-cli/src/ngtsc/program.ts

@@ -462,9 +462,15 @@ export class NgtscProgram implements api.Program {
   }
 
   private getTemplateDiagnostics(): ReadonlyArray<ts.Diagnostic> {
+    // Determine the strictness level of type checking based on compiler options. As
+    // `strictTemplates` is a superset of `fullTemplateTypeCheck`, the former implies the latter.
+    // Also see `verifyCompatibleTypeCheckOptions` where it is verified that `fullTemplateTypeCheck`
+    // is not disabled when `strictTemplates` is enabled.
+    const strictTemplates = !!this.options.strictTemplates;
+    const fullTemplateTypeCheck = strictTemplates || !!this.options.fullTemplateTypeCheck;
+
     // Skip template type-checking if it's disabled.
-    if (this.options.ivyTemplateTypeCheck === false &&
+    if (this.options.ivyTemplateTypeCheck === false && !fullTemplateTypeCheck) {
-        this.options.fullTemplateTypeCheck !== true) {
       return [];
     }
 
@@ -475,8 +481,7 @@ export class NgtscProgram implements api.Program {
     // First select a type-checking configuration, based on whether full template type-checking is
     // requested.
     let typeCheckingConfig: TypeCheckingConfig;
-    if (this.options.fullTemplateTypeCheck) {
+    if (fullTemplateTypeCheck) {
-      const strictTemplates = !!this.options.strictTemplates;
       typeCheckingConfig = {
         applyTemplateContextGuards: strictTemplates,
         checkQueries: false,

packages/compiler-cli/test/ngtsc/template_typecheck_spec.ts

@@ -245,7 +245,7 @@ export declare class AnimationEvent {
       });
 
       it('should check expressions and their type when overall strictness is enabled', () => {
-        env.tsconfig({fullTemplateTypeCheck: true, strictTemplates: true});
+        env.tsconfig({strictTemplates: true});
 
         const diags = env.driveDiagnostics();
         expect(diags.length).toBe(2);
@@ -303,7 +303,7 @@ export declare class AnimationEvent {
 
       it('should check expressions and their nullability when overall strictness is enabled',
          () => {
-           env.tsconfig({fullTemplateTypeCheck: true, strictTemplates: true});
+           env.tsconfig({strictTemplates: true});
 
            const diags = env.driveDiagnostics();
            expect(diags.length).toBe(2);
@@ -366,10 +366,7 @@ export declare class AnimationEvent {
 
       it('should infer result type for safe navigation expressions when overall strictness is enabled',
          () => {
-           env.tsconfig({
+           env.tsconfig({strictTemplates: true});
-             fullTemplateTypeCheck: true,
-             strictTemplates: true,
-           });
 
            const diags = env.driveDiagnostics();
            expect(diags.length).toBe(2);
@@ -429,7 +426,7 @@ export declare class AnimationEvent {
       });
 
       it('should expressions and infer type of $event when overall strictness is enabled', () => {
-        env.tsconfig({fullTemplateTypeCheck: true, strictTemplates: true});
+        env.tsconfig({strictTemplates: true});
 
         const diags = env.driveDiagnostics();
         expect(diags.length).toBe(2);
@@ -483,7 +480,7 @@ export declare class AnimationEvent {
 
       it('should check expressions and let $event be of type AnimationEvent when overall strictness is enabled',
          () => {
-           env.tsconfig({fullTemplateTypeCheck: true, strictTemplates: true});
+           env.tsconfig({strictTemplates: true});
 
            const diags = env.driveDiagnostics();
            expect(diags.length).toBe(2);
@@ -532,7 +529,7 @@ export declare class AnimationEvent {
       });
 
       it('should infer the type of DOM references when overall strictness is enabled', () => {
-        env.tsconfig({fullTemplateTypeCheck: true, strictTemplates: true});
+        env.tsconfig({strictTemplates: true});
 
         const diags = env.driveDiagnostics();
         expect(diags.length).toBe(1);
@@ -583,7 +580,7 @@ export declare class AnimationEvent {
       });
 
       it('should produce an error for text attributes when overall strictness is enabled', () => {
-        env.tsconfig({fullTemplateTypeCheck: true, strictTemplates: true});
+        env.tsconfig({strictTemplates: true});
 
         const diags = env.driveDiagnostics();
         expect(diags.length).toBe(2);
@@ -633,7 +630,7 @@ export declare class AnimationEvent {
 
       it('should check expressions and infer type of $event when overall strictness is enabled',
          () => {
-           env.tsconfig({fullTemplateTypeCheck: true, strictTemplates: true});
+           env.tsconfig({strictTemplates: true});
 
            const diags = env.driveDiagnostics();
            expect(diags.length).toBe(2);
@@ -776,7 +773,7 @@ export declare class AnimationEvent {
     });
 
     it('should accept NgFor iteration over a QueryList', () => {
-      env.tsconfig({fullTemplateTypeCheck: true, strictTemplates: true});
+      env.tsconfig({strictTemplates: true});
       env.write('test.ts', `
         import {CommonModule} from '@angular/common';
         import {Component, NgModule, QueryList} from '@angular/core';
@@ -800,7 +797,7 @@ export declare class AnimationEvent {
     });
 
     it('should infer the context of NgFor', () => {
-      env.tsconfig({fullTemplateTypeCheck: true, strictTemplates: true});
+      env.tsconfig({strictTemplates: true});
       env.write('test.ts', `
         import {CommonModule} from '@angular/common';
         import {Component, NgModule} from '@angular/core';
@@ -825,7 +822,7 @@ export declare class AnimationEvent {
     });
 
     it('should infer the context of NgIf', () => {
-      env.tsconfig({fullTemplateTypeCheck: true, strictTemplates: true});
+      env.tsconfig({strictTemplates: true});
       env.write('test.ts', `
         import {CommonModule} from '@angular/common';
         import {Component, NgModule} from '@angular/core';
@@ -1009,7 +1006,7 @@ export declare class AnimationEvent {
       });
 
       it('should be correctly inferred under strictTemplates', () => {
-        env.tsconfig({fullTemplateTypeCheck: true, strictTemplates: true});
+        env.tsconfig({strictTemplates: true});
 
         const diags = env.driveDiagnostics();
         expect(diags.length).toBe(1);