RFC#562 - {{and}}, {{or}}, {{not}} as keywords

Add boolean logic helpers and register them as built-in keywords
so they no longer need to be imported in strict-mode (gjs/gts) templates.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: NullVoxPopuli

packages/@ember/helper/index.ts

@@ -10,6 +10,9 @@ import {
   concat as glimmerConcat,
   get as glimmerGet,
   fn as glimmerFn,
+  and as glimmerAnd,
+  or as glimmerOr,
+  not as glimmerNot,
 } from '@glimmer/runtime';
 import { element as glimmerElement, uniqueId as glimmerUniqueId } from '@ember/-internals/glimmer';
 import { type Opaque } from '@ember/-internals/utility-types';
@@ -511,4 +514,75 @@ export interface ElementHelper extends Opaque<'helper:element'> {}
 export const uniqueId = glimmerUniqueId;
 export type UniqueIdHelper = typeof uniqueId;
 
+/**
+ * The `{{and}}` helper evaluates arguments left to right, returning the first
+ * falsy value (using Handlebars truthiness) or the right-most value if all
+ * are truthy. Requires at least two arguments.
+ *
+ * ```js
+ * import { and } from '@ember/helper';
+ *
+ * <template>
+ *   {{if (and @isAdmin @isLoggedIn) "Welcome, admin!" "Access denied"}}
+ * </template>
+ * ```
+ *
+ * In strict-mode (gjs/gts) templates, `and` is available as a keyword and
+ * does not need to be imported.
+ *
+ * @method and
+ * @param {unknown} args Two or more values to evaluate
+ * @return {unknown} The first falsy value or the last value
+ * @public
+ */
+export const and = glimmerAnd as unknown as AndHelper;
+export interface AndHelper extends Opaque<'helper:and'> {}
+
+/**
+ * The `{{or}}` helper evaluates arguments left to right, returning the first
+ * truthy value (using Handlebars truthiness) or the right-most value if all
+ * are falsy. Requires at least two arguments.
+ *
+ * ```js
+ * import { or } from '@ember/helper';
+ *
+ * <template>
+ *   {{if (or @hasAccess @isAdmin) "Welcome!" "No access"}}
+ * </template>
+ * ```
+ *
+ * In strict-mode (gjs/gts) templates, `or` is available as a keyword and
+ * does not need to be imported.
+ *
+ * @method or
+ * @param {unknown} args Two or more values to evaluate
+ * @return {unknown} The first truthy value or the last value
+ * @public
+ */
+export const or = glimmerOr as unknown as OrHelper;
+export interface OrHelper extends Opaque<'helper:or'> {}
+
+/**
+ * The `{{not}}` helper returns the logical negation of its argument using
+ * Handlebars truthiness. Takes exactly one argument.
+ *
+ * ```js
+ * import { not } from '@ember/helper';
+ *
+ * <template>
+ *   {{if (not @isDisabled) "Enabled" "Disabled"}}
+ * </template>
+ * ```
+ *
+ * In strict-mode (gjs/gts) templates, `not` is available as a keyword and
+ * does not need to be imported.
+ *
+ * @method not
+ * @param {unknown} value The value to negate
+ * @return {boolean}
+ * @public
+ */
+export const not = glimmerNot as unknown as NotHelper;
+export interface NotHelper extends Opaque<'helper:not'> {}
+
 /* eslint-enable @typescript-eslint/no-empty-object-type */

packages/@ember/template-compiler/lib/compile-options.ts

@@ -1,4 +1,4 @@
-import { fn } from '@ember/helper';
+import { and, fn, not, or } from '@ember/helper';
 import { on } from '@ember/modifier';
 import { assert } from '@ember/debug';
 import {
@@ -25,8 +25,11 @@ function malformedComponentLookup(string: string) {
 export const RUNTIME_KEYWORDS_NAME = '__ember_keywords__';
 
 export const keywords: Record<string, unknown> = {
+  and,
   fn,
+  not,
   on,
+  or,
 };
 
 function buildCompileOptions(_options: EmberPrecompileOptions): EmberPrecompileOptions {

packages/@ember/template-compiler/lib/plugins/auto-import-builtins.ts

@@ -30,11 +30,29 @@ export default function autoImportBuiltins(env: EmberASTPluginEnvironment): ASTP
         if (isFn(node, hasLocal)) {
           rewriteKeyword(env, node, 'fn', '@ember/helper');
         }
+        if (isAnd(node, hasLocal)) {
+          rewriteKeyword(env, node, 'and', '@ember/helper');
+        }
+        if (isOr(node, hasLocal)) {
+          rewriteKeyword(env, node, 'or', '@ember/helper');
+        }
+        if (isNot(node, hasLocal)) {
+          rewriteKeyword(env, node, 'not', '@ember/helper');
+        }
       },
       MustacheStatement(node: AST.MustacheStatement) {
         if (isFn(node, hasLocal)) {
           rewriteKeyword(env, node, 'fn', '@ember/helper');
         }
+        if (isAnd(node, hasLocal)) {
+          rewriteKeyword(env, node, 'and', '@ember/helper');
+        }
+        if (isOr(node, hasLocal)) {
+          rewriteKeyword(env, node, 'or', '@ember/helper');
+        }
+        if (isNot(node, hasLocal)) {
+          rewriteKeyword(env, node, 'not', '@ember/helper');
+        }
       },
     },
   };
@@ -68,3 +86,24 @@ function isFn(
 ): node is (AST.MustacheStatement | AST.SubExpression) & { path: AST.PathExpression } {
   return isPath(node.path) && node.path.original === 'fn' && !hasLocal('fn');
 }
+
+function isAnd(
+  node: AST.MustacheStatement | AST.SubExpression,
+  hasLocal: (k: string) => boolean
+): node is (AST.MustacheStatement | AST.SubExpression) & { path: AST.PathExpression } {
+  return isPath(node.path) && node.path.original === 'and' && !hasLocal('and');
+}
+
+function isOr(
+  node: AST.MustacheStatement | AST.SubExpression,
+  hasLocal: (k: string) => boolean
+): node is (AST.MustacheStatement | AST.SubExpression) & { path: AST.PathExpression } {
+  return isPath(node.path) && node.path.original === 'or' && !hasLocal('or');
+}
+
+function isNot(
+  node: AST.MustacheStatement | AST.SubExpression,
+  hasLocal: (k: string) => boolean
+): node is (AST.MustacheStatement | AST.SubExpression) & { path: AST.PathExpression } {
+  return isPath(node.path) && node.path.original === 'not' && !hasLocal('not');
+}

packages/@glimmer-workspace/integration-tests/test/keywords/and-runtime-test.ts

@@ -0,0 +1,54 @@
+import { jitSuite, RenderTest, test } from '@glimmer-workspace/integration-tests';
+
+import { template } from '@ember/template-compiler/runtime';
+
+class KeywordAndRuntime extends RenderTest {
+  static suiteName = 'keyword helper: and (runtime)';
+
+  @test
+  'explicit scope without import'() {
+    const compiled = template('{{if (and a b) "yes" "no"}}', {
+      strictMode: true,
+      scope: () => ({ a: true, b: true }),
+    });
+
+    this.renderComponent(compiled);
+    this.assertHTML('yes');
+  }
+
+  @test
+  'implicit scope (eval)'() {
+    let a = true;
+    let b = 'hello';
+
+    hide(a);
+    hide(b);
+
+    const compiled = template('{{if (and a b) "yes" "no"}}', {
+      strictMode: true,
+      eval() {
+        return eval(arguments[0]);
+      },
+    });
+
+    this.renderComponent(compiled);
+    this.assertHTML('yes');
+  }
+
+  @test
+  'returns falsy when one arg is falsy'() {
+    const compiled = template('{{if (and a b) "yes" "no"}}', {
+      strictMode: true,
+      scope: () => ({ a: true, b: 0 }),
+    });
+
+    this.renderComponent(compiled);
+    this.assertHTML('no');
+  }
+}
+
+jitSuite(KeywordAndRuntime);
+
+const hide = (variable: unknown) => {
+  new Function(`return (${JSON.stringify(variable)});`);
+};

packages/@glimmer-workspace/integration-tests/test/keywords/and-test.ts

@@ -0,0 +1,67 @@
+import { DEBUG } from '@glimmer/env';
+import { jitSuite, RenderTest, test } from '@glimmer-workspace/integration-tests';
+
+import { template } from '@ember/template-compiler';
+import { and } from '@ember/helper';
+
+class KeywordAnd extends RenderTest {
+  static suiteName = 'keyword helper: and';
+
+  @test
+  'returns right-most value when all are truthy'() {
+    const compiled = template('{{and a b}}', {
+      strictMode: true,
+      scope: () => ({ and, a: 1, b: 'hello' }),
+    });
+
+    this.renderComponent(compiled);
+    this.assertHTML('hello');
+  }
+
+  @test
+  'returns first falsy value'() {
+    const compiled = template('{{and a b}}', {
+      strictMode: true,
+      scope: () => ({ and, a: 0, b: 'hello' }),
+    });
+
+    this.renderComponent(compiled);
+    this.assertHTML('0');
+  }
+
+  @test
+  'works as a SubExpression with if'() {
+    const compiled = template('{{if (and a b) "yes" "no"}}', {
+      strictMode: true,
+      scope: () => ({ and, a: true, b: true }),
+    });
+
+    this.renderComponent(compiled);
+    this.assertHTML('yes');
+  }
+
+  @test
+  'treats empty array as falsy'() {
+    const compiled = template('{{if (and a b) "yes" "no"}}', {
+      strictMode: true,
+      scope: () => ({ and, a: true, b: [] }),
+    });
+
+    this.renderComponent(compiled);
+    this.assertHTML('no');
+  }
+
+  @test({ skip: !DEBUG })
+  'throws if called with less than two arguments'(assert: Assert) {
+    const compiled = template('{{and a}}', {
+      strictMode: true,
+      scope: () => ({ and, a: true }),
+    });
+
+    assert.throws(() => {
+      this.renderComponent(compiled);
+    }, /`and` expects at least two arguments/);
+  }
+}
+
+jitSuite(KeywordAnd);

packages/@glimmer-workspace/integration-tests/test/keywords/not-runtime-test.ts

@@ -0,0 +1,52 @@
+import { jitSuite, RenderTest, test } from '@glimmer-workspace/integration-tests';
+
+import { template } from '@ember/template-compiler/runtime';
+
+class KeywordNotRuntime extends RenderTest {
+  static suiteName = 'keyword helper: not (runtime)';
+
+  @test
+  'explicit scope without import'() {
+    const compiled = template('{{if (not a) "yes" "no"}}', {
+      strictMode: true,
+      scope: () => ({ a: false }),
+    });
+
+    this.renderComponent(compiled);
+    this.assertHTML('yes');
+  }
+
+  @test
+  'implicit scope (eval)'() {
+    let a = false;
+
+    hide(a);
+
+    const compiled = template('{{if (not a) "yes" "no"}}', {
+      strictMode: true,
+      eval() {
+        return eval(arguments[0]);
+      },
+    });
+
+    this.renderComponent(compiled);
+    this.assertHTML('yes');
+  }
+
+  @test
+  'returns no for truthy'() {
+    const compiled = template('{{if (not a) "yes" "no"}}', {
+      strictMode: true,
+      scope: () => ({ a: 'hello' }),
+    });
+
+    this.renderComponent(compiled);
+    this.assertHTML('no');
+  }
+}
+
+jitSuite(KeywordNotRuntime);
+
+const hide = (variable: unknown) => {
+  new Function(`return (${JSON.stringify(variable)});`);
+};

packages/@glimmer-workspace/integration-tests/test/keywords/not-test.ts

@@ -0,0 +1,56 @@
+import { DEBUG } from '@glimmer/env';
+import { jitSuite, RenderTest, test } from '@glimmer-workspace/integration-tests';
+
+import { template } from '@ember/template-compiler';
+import { not } from '@ember/helper';
+
+class KeywordNot extends RenderTest {
+  static suiteName = 'keyword helper: not';
+
+  @test
+  'returns true for falsy value'() {
+    const compiled = template('{{if (not a) "yes" "no"}}', {
+      strictMode: true,
+      scope: () => ({ not, a: false }),
+    });
+
+    this.renderComponent(compiled);
+    this.assertHTML('yes');
+  }
+
+  @test
+  'returns false for truthy value'() {
+    const compiled = template('{{if (not a) "yes" "no"}}', {
+      strictMode: true,
+      scope: () => ({ not, a: true }),
+    });
+
+    this.renderComponent(compiled);
+    this.assertHTML('no');
+  }
+
+  @test
+  'works with MustacheStatement'() {
+    const compiled = template('{{not a}}', {
+      strictMode: true,
+      scope: () => ({ not, a: false }),
+    });
+
+    this.renderComponent(compiled);
+    this.assertHTML('true');
+  }
+
+  @test({ skip: !DEBUG })
+  'throws if called with more than one argument'(assert: Assert) {
+    const compiled = template('{{not a b}}', {
+      strictMode: true,
+      scope: () => ({ not, a: true, b: false }),
+    });
+
+    assert.throws(() => {
+      this.renderComponent(compiled);
+    }, /`not` expects exactly one argument/);
+  }
+}
+
+jitSuite(KeywordNot);