From 8a9e9304c1aaa2dd37cbbea4e991ef892228f865 Mon Sep 17 00:00:00 2001
From: David Ferguson <davidferguson@users.noreply.github.com>
Date: Tue, 18 Jun 2019 08:39:41 +0100
Subject: [PATCH] fix(parser): fix issue with escaping backslashes when
 enableEscapeTags is set (#20)

there is a bug in the lexer where when enableEscapeTags is set, backslashes
are not always escaped (ie. \\[b] is treated as an escaped tag, rather than a
literal backslash, and then a tag).
---
 packages/bbob-parser/src/lexer.js       |  6 +++++-
 packages/bbob-parser/test/lexer.test.js | 23 +++++++++++++++++++++++
 packages/bbob-parser/test/parse.test.js | 22 +++++++++++++++++++++-
 3 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/packages/bbob-parser/src/lexer.js b/packages/bbob-parser/src/lexer.js
index 34255ca..f110b61 100644
--- a/packages/bbob-parser/src/lexer.js
+++ b/packages/bbob-parser/src/lexer.js
@@ -53,7 +53,7 @@ function createLexer(buffer, options = {}) {
   const RESERVED_CHARS = [closeTag, openTag, QUOTEMARK, BACKSLASH, SPACE, TAB, EQ, N, EM];
   const NOT_CHAR_TOKENS = [
     ...(options.enableEscapeTags ? [BACKSLASH] : []),
-    openTag, SPACE, TAB, N, BACKSLASH,
+    openTag, SPACE, TAB, N,
   ];
   const WHITESPACES = [SPACE, TAB];
   const SPECIAL_CHARS = [EQ, SPACE, TAB];
@@ -163,6 +163,10 @@ function createLexer(buffer, options = {}) {
       bufferGrabber.skip(); // skip the \ without emitting anything
       bufferGrabber.skip(); // skip past the [ or ] as well
       emitToken(createToken(TYPE_WORD, nextChar, row, col));
+    } else if (options.enableEscapeTags && currChar === BACKSLASH && nextChar === BACKSLASH) {
+      bufferGrabber.skip(); // skip the first \ without emitting anything
+      bufferGrabber.skip(); // skip past the second \ and emit it
+      emitToken(createToken(TYPE_WORD, nextChar, row, col));
     } else if (currChar === openTag) {
       bufferGrabber.skip(); // skip openTag
 
diff --git a/packages/bbob-parser/test/lexer.test.js b/packages/bbob-parser/test/lexer.test.js
index 1ee641d..3a92cff 100644
--- a/packages/bbob-parser/test/lexer.test.js
+++ b/packages/bbob-parser/test/lexer.test.js
@@ -305,6 +305,29 @@ describe('lexer', () => {
     expectOutput(output, tokens);
   });
 
+  test('escaped tag and escaped backslash', () => {
+    const tokenizeEscape = input => (createLexer(input, {
+      enableEscapeTags: true
+    }).tokenize());
+    const input = '\\\\\\[b\\\\\\]test\\\\\\[/b\\\\\\]';
+    const tokens = tokenizeEscape(input);
+    const output = [
+      [TYPE.WORD, '\\', '0', '0'],
+      [TYPE.WORD, '[', '0', '0'],
+      [TYPE.WORD, 'b', '0', '0'],
+      [TYPE.WORD, '\\', '0', '0'],
+      [TYPE.WORD, ']', '0', '0'],
+      [TYPE.WORD, 'test', '0', '0'],
+      [TYPE.WORD, '\\', '0', '0'],
+      [TYPE.WORD, '[', '0', '0'],
+      [TYPE.WORD, '/b', '0', '0'],
+      [TYPE.WORD, '\\', '0', '0'],
+      [TYPE.WORD, ']', '0', '0'],
+    ];
+
+    expectOutput(output, tokens);
+  });
+
   describe('html', () => {
     const tokenizeHTML = input => createLexer(input, { openTag: '<', closeTag: '>' }).tokenize();
 
diff --git a/packages/bbob-parser/test/parse.test.js b/packages/bbob-parser/test/parse.test.js
index 8ada554..00f3e8c 100644
--- a/packages/bbob-parser/test/parse.test.js
+++ b/packages/bbob-parser/test/parse.test.js
@@ -184,7 +184,7 @@ describe('Parser', () => {
       ]);
     });
 
-    test('parse escaped tags tags', () => {
+    test('parse escaped tags', () => {
       const ast = parse('\\[b\\]test\\[/b\\]', {
         enableEscapeTags: true
       });
@@ -199,5 +199,25 @@ describe('Parser', () => {
         ']',
       ]);
     });
+
+    test('parse escaped tags and escaped backslash', () => {
+      const ast = parse('\\\\\\[b\\\\\\]test\\\\\\[/b\\\\\\]', {
+        enableEscapeTags: true
+      });
+
+      expectOutput(ast, [
+        '\\',
+        '[',
+        'b',
+        '\\',
+        ']',
+        'test',
+        '\\',
+        '[',
+        '/b',
+        '\\',
+        ']',
+      ]);
+    });
   });
 });