From de129283a5ac18b34ec856f6ee94d04f3bbe658f Mon Sep 17 00:00:00 2001
From: Phil Pluckthun <phil@kitten.sh>
Date: Sat, 9 Jan 2021 03:01:18 +0000
Subject: [PATCH] Add shorthand support to parsers

---
 src/parser.js      | 21 ++++++++-----
 src/parser.test.js | 77 +++++++++++++++++++++++++++++++++++++---------
 2 files changed, 76 insertions(+), 22 deletions(-)

diff --git a/src/parser.js b/src/parser.js
index 6059a3e..d37e274 100644
--- a/src/parser.js
+++ b/src/parser.js
@@ -12,6 +12,7 @@ export const parse = (quasis, expressions) => {
   let currentGroup = null;
   let lastMatch;
   let currentSequence = rootSequence;
+  let capture;
 
   for (
     let quasiIndex = 0, stackIndex = 0;
@@ -19,9 +20,9 @@ export const parse = (quasis, expressions) => {
     stackIndex++
   ) {
     if (stackIndex % 2 !== 0) {
-      currentSequence.push({
-        expression: expressions[stackIndex++ >> 1],
-      });
+      const expression = expressions[stackIndex++ >> 1];
+      currentSequence.push({ expression, capture });
+      capture = undefined;
     }
 
     const quasi = quasis[stackIndex >> 1];
@@ -36,12 +37,18 @@ export const parse = (quasis, expressions) => {
         if (!currentSequence) syntaxError(char);
       } else if (char === '(') {
         sequenceStack.push(currentSequence);
-        currentSequence.push((currentGroup = { sequence: [] }));
+        currentSequence.push((currentGroup = { sequence: [], capture }));
         currentSequence = currentGroup.sequence;
+        capture = undefined;
+      } else if (char === ':' || char === '=' || char === '!') {
+        capture = char;
+        const nextChar = quasi[quasiIndex];
+        if (quasi[quasiIndex] && quasi[quasiIndex] !== '(') syntaxError(char);
       } else if (char === '?' && !currentSequence.length && currentGroup) {
-        const nextChar = quasi[quasiIndex++];
-        if (nextChar === ':' || nextChar === '=' || nextChar === '!') {
-          currentGroup.capture = nextChar;
+        capture = quasi[quasiIndex++];
+        if (capture === ':' || capture === '=' || capture === '!') {
+          currentGroup.capture = capture;
+          capture = undefined;
         } else {
           syntaxError(char);
         }
diff --git a/src/parser.test.js b/src/parser.test.js
index 54e0abd..c8029ec 100644
--- a/src/parser.test.js
+++ b/src/parser.test.js
@@ -42,38 +42,85 @@ it('supports groups with quantifiers', () => {
   expect(ast).toHaveProperty('0.sequence.0.quantifier', undefined);
 });
 
-it('supports non-capturing groups', () => {
-  const ast = parseTag`(?: ${1})`;
-  expect(ast).toHaveProperty('length', 1);
-  expect(ast).toHaveProperty('0.capture', ':');
-  expect(ast).toHaveProperty('0.sequence.length', 1);
+describe('non-capturing syntax', () => {
+  it('supports regex-like syntax', () => {
+    const ast = parseTag`(?: ${1})`;
+    expect(ast).toHaveProperty('length', 1);
+    expect(ast).toHaveProperty('0.capture', ':');
+    expect(ast).toHaveProperty('0.sequence.length', 1);
+  });
+
+  it('supports shorthand', () => {
+    let ast = parseTag`:${1}`;
+    expect(ast).toHaveProperty('length', 1);
+    expect(ast).toHaveProperty('0.capture', ':');
+    expect(ast).toHaveProperty('0.expression', 1);
+    ast = parseTag`:(${1})`;
+    expect(ast).toHaveProperty('length', 1);
+    expect(ast).toHaveProperty('0.capture', ':');
+    expect(ast).toHaveProperty('0.sequence.length', 1);
+  });
+
+  it('fails on invalid usage', () => {
+    expect(() => parseTag`${1} : ${2}`).toThrow();
+    expect(() => parseTag`${1} :|${2}`).toThrow();
+  });
 });
 
-it('supports positive lookahead groups', () => {
-  const ast = parseTag`(?= ${1})`;
-  expect(ast).toHaveProperty('length', 1);
-  expect(ast).toHaveProperty('0.capture', '=');
-  expect(ast).toHaveProperty('0.sequence.length', 1);
+describe('positive lookaheads syntax', () => {
+  it('supports regex-like syntax', () => {
+    const ast = parseTag`(?= ${1})`;
+    expect(ast).toHaveProperty('length', 1);
+    expect(ast).toHaveProperty('0.capture', '=');
+    expect(ast).toHaveProperty('0.sequence.length', 1);
+  });
+
+  it('supports shorthand', () => {
+    let ast = parseTag`=${1}`;
+    expect(ast).toHaveProperty('length', 1);
+    expect(ast).toHaveProperty('0.capture', '=');
+    expect(ast).toHaveProperty('0.expression', 1);
+    ast = parseTag`=(${1})`;
+    expect(ast).toHaveProperty('length', 1);
+    expect(ast).toHaveProperty('0.capture', '=');
+    expect(ast).toHaveProperty('0.sequence.length', 1);
+  });
 });
 
-it('supports negative lookahead groups', () => {
-  const ast = parseTag`(?! ${1})`;
-  expect(ast).toHaveProperty('length', 1);
-  expect(ast).toHaveProperty('0.capture', '!');
-  expect(ast).toHaveProperty('0.sequence.length', 1);
+describe('negative lookaheads syntax', () => {
+  it('supports regex-like syntax', () => {
+    const ast = parseTag`(?! ${1})`;
+    expect(ast).toHaveProperty('length', 1);
+    expect(ast).toHaveProperty('0.capture', '!');
+    expect(ast).toHaveProperty('0.sequence.length', 1);
+  });
+
+  it('supports shorthand', () => {
+    let ast = parseTag`!${1}`;
+    expect(ast).toHaveProperty('length', 1);
+    expect(ast).toHaveProperty('0.capture', '!');
+    expect(ast).toHaveProperty('0.expression', 1);
+    ast = parseTag`!(${1})`;
+    expect(ast).toHaveProperty('length', 1);
+    expect(ast).toHaveProperty('0.capture', '!');
+    expect(ast).toHaveProperty('0.sequence.length', 1);
+  });
 });
 
 it('supports groups with alternates', () => {
   expect(parseTag`(${1} | ${2}) ${3}`).toMatchInlineSnapshot(`
     Array [
       Object {
+        "capture": undefined,
         "sequence": Array [
           Object {
+            "capture": undefined,
             "expression": 1,
           },
         ],
       },
       Object {
+        "capture": undefined,
         "expression": 3,
       },
     ]
-- 
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