feat: Void matcher for handlers (#107)

* feat: Void matcher for handlers

* Bump to 1.1.16

Author: zharinov

lib/query/builder.ts

@@ -6,7 +6,11 @@ import {
   SeqMatcher,
   SymMatcher,
 } from './matchers';
-import { BeginMatcher, EndMatcher } from './matchers/anchor-matcher';
+import {
+  BeginMatcher,
+  EndMatcher,
+  VoidMatcher,
+} from './matchers/anchor-matcher';
 import { CommentMatcher } from './matchers/comment-matcher';
 import { NumMatcher } from './matchers/num-matcher';
 import {
@@ -173,6 +177,12 @@ abstract class AbstractBuilder<Ctx> extends TerminalBuilder<Ctx> {
     const builder = new SeqBuilder(this, other);
     return builder;
   }
+
+  handler(fn: (context: Ctx) => Ctx): SeqBuilder<Ctx> {
+    const voidMatcher = new VoidBuilder(fn);
+    const builder = new SeqBuilder(this, voidMatcher);
+    return builder;
+  }
 }
 
 // Anchors
@@ -200,6 +210,20 @@ export function begin<Ctx>(): BeginBuilder<Ctx> {
   return new BeginBuilder<Ctx>();
 }
 
+class VoidBuilder<Ctx> extends AbstractBuilder<Ctx> {
+  constructor(private readonly fn: (context: Ctx) => Ctx) {
+    super();
+  }
+
+  build(): VoidMatcher<Ctx> {
+    return new VoidMatcher<Ctx>(this.fn);
+  }
+}
+
+export function handler<Ctx>(fn: (context: Ctx) => Ctx): VoidBuilder<Ctx> {
+  return new VoidBuilder(fn);
+}
+
 // Sequence
 
 class SeqBuilder<Ctx> extends AbstractBuilder<Ctx> {

lib/query/matchers/anchor-matcher.spec.ts

@@ -30,4 +30,14 @@ describe('query/matchers/anchor-matcher', () => {
     const res = lang.query(input, query, []);
     expect(res).toBeUndefined();
   });
+
+  it('supports handler builder', () => {
+    const input = 'baz';
+    const query = q
+      .handler<Ctx>((ctx) => [...ctx, 'bar'])
+      .sym(handler)
+      .handler((ctx) => ctx.map((x) => x.toUpperCase()));
+    const res = lang.query(input, query, ['foo']);
+    expect(res).toEqual(['FOO', 'BAR', 'BAZ']);
+  });
 });

lib/query/matchers/anchor-matcher.ts

@@ -1,3 +1,5 @@
+import type { Cursor } from '../../parser';
+import { clone } from '../../util/clone';
 import type { Checkpoint } from '../types';
 import { AbstractMatcher } from './abstract-matcher';
 
@@ -26,3 +28,26 @@ export class EndMatcher<Ctx> extends AbstractMatcher<Ctx> {
     return null;
   }
 }
+
+export class VoidMatcher<Ctx> extends AbstractMatcher<Ctx> {
+  private handler: (context: Ctx) => Ctx;
+
+  constructor(handler: (context: Ctx) => Ctx) {
+    super();
+    this.handler = (context: Ctx) => handler(clone(context));
+  }
+
+  match(checkpoint: Checkpoint<Ctx>): Checkpoint<Ctx> | null {
+    const { cursor, context } = checkpoint;
+    const newContext = this.handler(context);
+    return { cursor, context: newContext };
+  }
+
+  override moveRight(cursor: Cursor): Cursor {
+    return cursor;
+  }
+
+  override seekNext(cursor: Cursor): Cursor {
+    return cursor;
+  }
+}

package.json

@@ -1,7 +1,7 @@
 {
   "name": "good-enough-parser",
   "description": "Parse and query computer programs source code",
-  "version": "1.1.15",
+  "version": "1.1.16",
   "repository": "git@github.com:zharinov/good-enough-parser.git",
   "author": "Sergei Zharinov",
   "contributors": [