feat(typescript-estree): add parseWithNodeMaps API (#2760)

Ref: prettier/prettier#9636

This allows consumers to reach into the underlying TS AST in cases where our AST doesn't quite solve the use case.

Motivating example:

We don't (currently) error for code unless TS itself throws an error.
TS is _very_ permissive, but that leads to some weird (and invalid) code we don't error for, and don't include in the AST.
For example - this is _syntactically_ valid in the TS parser, but they emit a _semantic_ error:
```ts
@decorator
enum Foo {
  A = 1
}
```
As it's not a valid place for a decorator - we do not emit its information in the ESTree AST, but as TS treats this as a semantic error - it is parse-time valid.
This creates weird states for consumers wherein they cannot see a decorator exists there, which can cause them to ignore it entirely.
For linting - this isn't a problem. But for something like prettier - this means that they'll delete the decorator at format time!
This is very bad.

Until we implement a solution for #1852 - this will allow consumers to bridge the gap themselves.

Author: bradzacher

packages/typescript-estree/README.md

@@ -220,6 +220,18 @@ interface ParseAndGenerateServicesOptions extends ParseOptions {
   createDefaultProgram?: boolean;
 }
 
+interface ParserServices {
+  program: ts.Program;
+  esTreeNodeToTSNodeMap: WeakMap<TSESTree.Node, ts.Node | ts.Token>;
+  tsNodeToESTreeNodeMap: WeakMap<ts.Node | ts.Token, TSESTree.Node>;
+  hasFullTypeInformation: boolean;
+}
+
+interface ParseAndGenerateServicesResult<T extends TSESTreeOptions> {
+  ast: TSESTree.Program;
+  services: ParserServices;
+}
+
 const PARSE_AND_GENERATE_SERVICES_DEFAULT_OPTIONS: ParseOptions = {
   ...PARSE_DEFAULT_OPTIONS,
   errorOnTypeScriptSyntacticAndSemanticIssues: false,
@@ -233,7 +245,7 @@ const PARSE_AND_GENERATE_SERVICES_DEFAULT_OPTIONS: ParseOptions = {
 declare function parseAndGenerateServices(
   code: string,
   options: ParseOptions = PARSE_DEFAULT_OPTIONS,
-): TSESTree.Program;
+): ParseAndGenerateServicesResult;
 ```
 
 Example usage:
@@ -242,14 +254,47 @@ Example usage:
 import { parseAndGenerateServices } from '@typescript-eslint/typescript-estree';
 
 const code = `const hello: string = 'world';`;
-const ast = parseAndGenerateServices(code, {
+const { ast, services } = parseAndGenerateServices(code, {
   filePath: '/some/path/to/file/foo.ts',
   loc: true,
   project: './tsconfig.json',
   range: true,
 });
 ```
 
+#### `parseWithNodeMaps(code, options)`
+
+Parses the given string of code with the options provided and returns both the ESTree-compatible AST as well as the node maps.
+This allows you to work with both ASTs without the overhead of types that may come with `parseAndGenerateServices`.
+
+```ts
+interface ParseWithNodeMapsResult<T extends TSESTreeOptions> {
+  ast: TSESTree.Program;
+  esTreeNodeToTSNodeMap: ParserServices['esTreeNodeToTSNodeMap'];
+  tsNodeToESTreeNodeMap: ParserServices['tsNodeToESTreeNodeMap'];
+}
+
+declare function parseWithNodeMaps(
+  code: string,
+  options: ParseOptions = PARSE_DEFAULT_OPTIONS,
+): ParseWithNodeMapsResult;
+```
+
+Example usage:
+
+```js
+import { parseWithNodeMaps } from '@typescript-eslint/typescript-estree';
+
+const code = `const hello: string = 'world';`;
+const { ast, esTreeNodeToTSNodeMap, tsNodeToESTreeNodeMap } = parseWithNodeMaps(
+  code,
+  {
+    loc: true,
+    range: true,
+  },
+);
+```
+
 ### `TSESTree`, `AST_NODE_TYPES` and `AST_TOKEN_TYPES`
 
 Types for the AST produced by the parse functions.

packages/typescript-estree/src/index.ts

@@ -1,9 +1,4 @@
-export {
-  AST,
-  parse,
-  parseAndGenerateServices,
-  ParseAndGenerateServicesResult,
-} from './parser';
+export * from './parser';
 export { ParserServices, TSESTreeOptions } from './parser-options';
 export { simpleTraverse } from './simple-traverse';
 export * from './ts-estree';

packages/typescript-estree/src/parser.ts

@@ -321,11 +321,24 @@ interface ParseAndGenerateServicesResult<T extends TSESTreeOptions> {
   ast: AST<T>;
   services: ParserServices;
 }
+interface ParseWithNodeMapsResult<T extends TSESTreeOptions> {
+  ast: AST<T>;
+  esTreeNodeToTSNodeMap: ParserServices['esTreeNodeToTSNodeMap'];
+  tsNodeToESTreeNodeMap: ParserServices['tsNodeToESTreeNodeMap'];
+}
 
 function parse<T extends TSESTreeOptions = TSESTreeOptions>(
   code: string,
   options?: T,
 ): AST<T> {
+  const { ast } = parseWithNodeMaps(code, options);
+  return ast;
+}
+
+function parseWithNodeMaps<T extends TSESTreeOptions = TSESTreeOptions>(
+  code: string,
+  options?: T,
+): ParseWithNodeMapsResult<T> {
   /**
    * Reset the parse configuration
    */
@@ -367,8 +380,13 @@ function parse<T extends TSESTreeOptions = TSESTreeOptions>(
   /**
    * Convert the TypeScript AST to an ESTree-compatible one
    */
-  const { estree } = astConverter(ast, extra, false);
-  return estree as AST<T>;
+  const { estree, astMaps } = astConverter(ast, extra, false);
+
+  return {
+    ast: estree as AST<T>,
+    esTreeNodeToTSNodeMap: astMaps.esTreeNodeToTSNodeMap,
+    tsNodeToESTreeNodeMap: astMaps.tsNodeToESTreeNodeMap,
+  };
 }
 
 function parseAndGenerateServices<T extends TSESTreeOptions = TSESTreeOptions>(
@@ -450,4 +468,11 @@ function parseAndGenerateServices<T extends TSESTreeOptions = TSESTreeOptions>(
   };
 }
 
-export { AST, parse, parseAndGenerateServices, ParseAndGenerateServicesResult };
+export {
+  AST,
+  parse,
+  parseAndGenerateServices,
+  parseWithNodeMaps,
+  ParseAndGenerateServicesResult,
+  ParseWithNodeMapsResult,
+};