Add 'Symbol.toStringTag' into every exported class

.eslintrc.yml

@@ -22,6 +22,7 @@ rules:
 
   internal-rules/only-ascii: error
   internal-rules/no-dir-import: error
+  internal-rules/require-to-string-tag: off
 
   ##############################################################################
   # `eslint-plugin-istanbul` rule list based on `v0.1.2`
@@ -610,8 +611,12 @@ overrides:
       '@typescript-eslint/space-before-function-paren': off
       '@typescript-eslint/space-infix-ops': off
       '@typescript-eslint/type-annotation-spacing': off
+  - files: 'src/**'
+    rules:
+      internal-rules/require-to-string-tag: error
   - files: 'src/**/__*__/**'
     rules:
+      internal-rules/require-to-string-tag: off
       node/no-unpublished-import: [error, { allowModules: ['chai', 'mocha'] }]
       import/no-restricted-paths: off
       import/no-extraneous-dependencies: [error, { devDependencies: true }]

resources/eslint-internal-rules/index.js

@@ -2,10 +2,12 @@
 
 const onlyASCII = require('./only-ascii.js');
 const noDirImport = require('./no-dir-import.js');
+const requireToStringTag = require('./require-to-string-tag.js');
 
 module.exports = {
   rules: {
     'only-ascii': onlyASCII,
     'no-dir-import': noDirImport,
+    'require-to-string-tag': requireToStringTag,
   },
 };

resources/eslint-internal-rules/require-to-string-tag.js

@@ -0,0 +1,25 @@
+'use strict';
+
+module.exports = function requireToStringTag(context) {
+  const sourceCode = context.getSourceCode();
+
+  return {
+    'ExportNamedDeclaration > ClassDeclaration': (classNode) => {
+      const hasToStringTag = classNode.body.body.some((property) => {
+        if (property.type !== 'MethodDefinition' || property.kind !== 'get') {
+          return false;
+        }
+        const keyText = sourceCode.getText(property.key);
+        return keyText === 'Symbol.toStringTag';
+      });
+
+      if (!hasToStringTag) {
+        context.report({
+          node: classNode,
+          message:
+            'All exported classes required to have [Symbol.toStringTag] method',
+        });
+      }
+    },
+  };
+};

src/language/ast.ts

@@ -42,6 +42,10 @@ export class Location {
   toJSON(): { start: number; end: number } {
     return { start: this.start, end: this.end };
   }
+
+  get [Symbol.toStringTag]() {
+    return 'Location';
+  }
 }
 
 /**
@@ -121,6 +125,10 @@ export class Token {
       column: this.column,
     };
   }
+
+  get [Symbol.toStringTag]() {
+    return 'Token';
+  }
 }
 
 /**

src/language/lexer.ts

@@ -79,6 +79,10 @@ export class Lexer {
     }
     return token;
   }
+
+  get [Symbol.toStringTag]() {
+    return 'Lexer';
+  }
 }
 
 /**

src/language/parser.ts

@@ -1520,6 +1520,10 @@ export class Parser {
     } while (this.expectOptionalToken(delimiterKind));
     return nodes;
   }
+
+  get [Symbol.toStringTag]() {
+    return 'Parser';
+  }
 }
 
 /**

src/utilities/TypeInfo.ts

@@ -292,6 +292,10 @@ export class TypeInfo {
         break;
     }
   }
+
+  get [Symbol.toStringTag]() {
+    return 'TypeInfo';
+  }
 }
 
 type GetFieldDefFn = (

src/validation/ValidationContext.ts

@@ -131,6 +131,10 @@ export class ASTValidationContext {
     }
     return fragments;
   }
+
+  get [Symbol.toStringTag]() {
+    return 'ASTValidationContext';
+  }
 }
 
 export type ASTValidationRule = (context: ASTValidationContext) => ASTVisitor;
@@ -150,6 +154,10 @@ export class SDLValidationContext extends ASTValidationContext {
   getSchema(): Maybe<GraphQLSchema> {
     return this._schema;
   }
+
+  get [Symbol.toStringTag]() {
+    return 'SDLValidationContext';
+  }
 }
 
 export type SDLValidationRule = (context: SDLValidationContext) => ASTVisitor;
@@ -253,6 +261,10 @@ export class ValidationContext extends ASTValidationContext {
   getEnumValue(): Maybe<GraphQLEnumValue> {
     return this._typeInfo.getEnumValue();
   }
+
+  get [Symbol.toStringTag]() {
+    return 'ValidationContext';
+  }
 }
 
 export type ValidationRule = (context: ValidationContext) => ASTVisitor;