Feb 17, 2025 · Feb 4, 2025
diff --git a/packages/eslint-plugin/docs/rules/no-unnecessary-template-expression.mdx b/packages/eslint-plugin/docs/rules/no-unnecessary-template-expression.mdx
  C = 'C',
 }
 type ABCUnion = `${ABC}`;
 type A = `${ABC.A}`;

 // Interpolating type parameters is allowed.
 type TextUtil<T extends string> = `${T}`;
diff --git a/packages/eslint-plugin/src/rules/no-unnecessary-template-expression.ts b/packages/eslint-plugin/src/rules/no-unnecessary-template-expression.ts
 import type { TSESLint } from '@typescript-eslint/utils';

 import { TSESTree, AST_NODE_TYPES } from '@typescript-eslint/utils';
 import * as tsutils from 'ts-api-utils';
 import * as ts from 'typescript';

 import {
      return isStringLike(type);
    }

    /**
     * Checks for whole enum types, i.e. `MyEnum`, and not their values, i.e. `MyEnum.A`
     */
    function isEnumType(type: ts.Type): boolean {
      const symbol = type.getSymbol();

      return !!(
        symbol?.valueDeclaration &&
        ts.isEnumDeclaration(symbol.valueDeclaration)
      );
    function isEnumMemberType(type: ts.Type): boolean {
      return tsutils.typeParts(type).some(t => {
        const symbol = t.getSymbol();
        return !!(
          symbol?.valueDeclaration && ts.isEnumMember(symbol.valueDeclaration)
        );
      });
    }

    const isLiteral = isNodeOfType(TSESTree.AST_NODE_TYPES.Literal);
            constraintType &&
            !isTypeParameter &&
            isUnderlyingTypeString(constraintType) &&
            !isEnumType(constraintType)
            !isEnumMemberType(constraintType)
          ) {
            reportSingleInterpolation(node);
            return;
diff --git a/.../eslint-plugin/tests/docs-eslint-output-snapshots/no-unnecessary-template-expression.shot b/.../eslint-plugin/tests/docs-eslint-output-snapshots/no-unnecessary-template-expression.shot
diff --git a/packages/eslint-plugin/tests/rules/no-unnecessary-template-expression.test.ts b/packages/eslint-plugin/tests/rules/no-unnecessary-template-expression.test.ts
  A = 1,
  B = 2,
 }
 type Bar = \`\${Foo.A}\`;
    `,
    `
 enum Enum1 {
  A = 'A1',
  B = 'B1',
 }

 enum Enum2 {
  A = 'A2',
  B = 'B2',
 }

 type Union = \`\${Enum1 | Enum2}\`;
    `,
    `
 enum Enum1 {
  A = 'A1',
  B = 'B1',
 }

 enum Enum2 {
  A = 'A2',
  B = 'B2',
 }

 type Union = \`\${Enum1.A | Enum2.B}\`;
    `,
    `
 enum Enum1 {
  A = 'A1',
  B = 'B1',
 }

 enum Enum2 {
  A = 'A2',
  B = 'B2',
 }
 type Enums = Enum1 | Enum2;
 type Union = \`\${Enums}\`;
    `,
    `
 enum Enum {
  A = 'A',
  B = 'A',
 }

 type Intersection = \`\${Enum1.A & string}\`;
    `,
    `
 enum Foo {
  A = 'A',
  B = 'B',
 }
 type Bar = \`\${Foo.A}\`;
    `,
    `
      ],
      output: "type FooBar = 'foo' | 'bar';",
    },
    {
      code: `
 enum Foo {
  A = 'A',
  B = 'B',
 }
 type Bar = \`\${Foo.A}\`;
      `,
      errors: [
        {
          column: 13,
          endColumn: 21,
          endLine: 6,
          line: 6,
          messageId: 'noUnnecessaryTemplateExpression',
        },
      ],
      output: `
 enum Foo {
  A = 'A',
  B = 'B',
 }
 type Bar = Foo.A;
      `,
    },
  ],
 });
Original file line number	Diff line number	Diff line change
Expand Up		@@ -66,6 +66,7 @@ enum ABC {
		C = 'C',
		}
		type ABCUnion = `${ABC}`;
		type A = `${ABC.A}`;

		// Interpolating type parameters is allowed.
		type TextUtil<T extends string> = `${T}`;
Expand Down
Original file line number	Diff line number	Diff line change
		@@ -1,6 +1,7 @@
		import type { TSESLint } from '@typescript-eslint/utils';

		import { TSESTree, AST_NODE_TYPES } from '@typescript-eslint/utils';
		import * as tsutils from 'ts-api-utils';
		import * as ts from 'typescript';

		import {
Expand DownExpand Up		@@ -76,16 +77,13 @@ export default createRule<[], MessageId>({
		return isStringLike(type);
		}

		/**
		* Checks for whole enum types, i.e. `MyEnum`, and not their values, i.e. `MyEnum.A`
		*/
		function isEnumType(type: ts.Type): boolean {
		const symbol = type.getSymbol();

		return !!(
		symbol?.valueDeclaration &&
		ts.isEnumDeclaration(symbol.valueDeclaration)
		);
		function isEnumMemberType(type: ts.Type): boolean {
		return tsutils.typeParts(type).some(t => {
		const symbol = t.getSymbol();
		return !!(
		symbol?.valueDeclaration && ts.isEnumMember(symbol.valueDeclaration)
		);
		});
		}

		const isLiteral = isNodeOfType(TSESTree.AST_NODE_TYPES.Literal);
Expand DownExpand Up		@@ -460,7 +458,7 @@ export default createRule<[], MessageId>({
		constraintType &&
		!isTypeParameter &&
		isUnderlyingTypeString(constraintType) &&
		!isEnumType(constraintType)
		!isEnumMemberType(constraintType)
		) {
		reportSingleInterpolation(node);
		return;
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1188,6 +1188,60 @@ enum Foo {
		A = 1,
		B = 2,
		}
		type Bar = \`\${Foo.A}\`;
		`,
		`
		enum Enum1 {
		A = 'A1',
		B = 'B1',
		}

		enum Enum2 {
		A = 'A2',
		B = 'B2',
		}

		type Union = \`\${Enum1 \| Enum2}\`;
		`,
		`
		enum Enum1 {
		A = 'A1',
		B = 'B1',
		}

		enum Enum2 {
		A = 'A2',
		B = 'B2',
		}

		type Union = \`\${Enum1.A \| Enum2.B}\`;
		`,
		`
		enum Enum1 {
		A = 'A1',
		B = 'B1',
		}

		enum Enum2 {
		A = 'A2',
		B = 'B2',
		}
		type Enums = Enum1 \| Enum2;
		type Union = \`\${Enums}\`;
		`,
		`
		enum Enum {
		A = 'A',
		B = 'A',
		}

		type Intersection = \`\${Enum1.A & string}\`;
		`,
		`
		enum Foo {
		A = 'A',
		B = 'B',
		}
		type Bar = \`\${Foo.A}\`;
		`,
		`
Expand DownExpand Up		@@ -1412,30 +1466,5 @@ type Bar = Foo;
		],
		output: "type FooBar = 'foo' \| 'bar';",
		},
		{
		code: `
		enum Foo {
		A = 'A',
		B = 'B',
		}
		type Bar = \`\${Foo.A}\`;
		`,
		errors: [
		{
		column: 13,
		endColumn: 21,
		endLine: 6,
		line: 6,
		messageId: 'noUnnecessaryTemplateExpression',
		},
		],
		output: `
		enum Foo {
		A = 'A',
		B = 'B',
		}
		type Bar = Foo.A;
		`,
		},
		],
		});