Fix tab behavior inside blockquotes

lib/rules_block/blockquote.js

@@ -6,9 +6,25 @@ var isSpace = require('../common/utils').isSpace;
 
 
 module.exports = function blockquote(state, startLine, endLine, silent) {
-  var nextLine, lastLineEmpty, oldTShift, oldSCount, oldBMarks, oldIndent, oldParentType, lines, initial, offset, ch,
+  var adjustTab,
-      terminatorRules, token,
+      ch,
-      i, l, terminate,
+      i,
+      initial,
+      l,
+      lastLineEmpty,
+      lines,
+      nextLine,
+      offset,
+      oldBMarks,
+      oldBSCount,
+      oldIndent,
+      oldParentType,
+      oldSCount,
+      oldTShift,
+      spaceAfterMarker,
+      terminate,
+      terminatorRules,
+      token,
       pos = state.bMarks[startLine] + state.tShift[startLine],
       max = state.eMarks[startLine];
 
@@ -19,15 +35,41 @@ module.exports = function blockquote(state, startLine, endLine, silent) {
   // so no point trying to find the end of it in silent mode
   if (silent) { return true; }
 
-  // skip one optional space (but not tab, check cmark impl) after '>'
-  if (state.src.charCodeAt(pos) === 0x20) { pos++; }
-
   oldIndent = state.blkIndent;
   state.blkIndent = 0;
 
   // skip spaces after ">" and re-calculate offset
   initial = offset = state.sCount[startLine] + pos - (state.bMarks[startLine] + state.tShift[startLine]);
 
+  // skip one optional space after '>'
+  if (state.src.charCodeAt(pos) === 0x20 /* space */) {
+    // ' >   test '
+    //     ^ -- position start of line here:
+    pos++;
+    initial++;
+    offset++;
+    adjustTab = false;
+    spaceAfterMarker = true;
+  } else if (state.src.charCodeAt(pos) === 0x09 /* tab */) {
+    spaceAfterMarker = true;
+
+    if ((state.bsCount[startLine] + offset) % 4 === 3) {
+      // '  >\t  test '
+      //       ^ -- position start of line here (tab has width===1)
+      pos++;
+      initial++;
+      offset++;
+      adjustTab = false;
+    } else {
+      // ' >\t  test '
+      //    ^ -- position start of line here + shift bsCount slightly
+      //         to make extra space appear
+      adjustTab = true;
+    }
+  } else {
+    spaceAfterMarker = false;
+  }
+
   oldBMarks = [ state.bMarks[startLine] ];
   state.bMarks[startLine] = pos;
 
@@ -36,7 +78,7 @@ module.exports = function blockquote(state, startLine, endLine, silent) {
 
     if (isSpace(ch)) {
       if (ch === 0x09) {
-        offset += 4 - offset % 4;
+        offset += 4 - (offset + state.bsCount[startLine] + (adjustTab ? 1 : 0)) % 4;
       } else {
         offset++;
       }
@@ -47,6 +89,9 @@ module.exports = function blockquote(state, startLine, endLine, silent) {
     pos++;
   }
 
+  oldBSCount = [ state.bsCount[startLine] ];
+  state.bsCount[startLine] = state.sCount[startLine] + 1 + (spaceAfterMarker ? 1 : 0);
+
   lastLineEmpty = pos >= max;
 
   oldSCount = [ state.sCount[startLine] ];
@@ -92,12 +137,38 @@ module.exports = function blockquote(state, startLine, endLine, silent) {
     if (state.src.charCodeAt(pos++) === 0x3E/* > */) {
       // This line is inside the blockquote.
 
-      // skip one optional space (but not tab, check cmark impl) after '>'
-      if (state.src.charCodeAt(pos) === 0x20) { pos++; }
-
       // skip spaces after ">" and re-calculate offset
       initial = offset = state.sCount[nextLine] + pos - (state.bMarks[nextLine] + state.tShift[nextLine]);
 
+      // skip one optional space after '>'
+      if (state.src.charCodeAt(pos) === 0x20 /* space */) {
+        // ' >   test '
+        //     ^ -- position start of line here:
+        pos++;
+        initial++;
+        offset++;
+        adjustTab = false;
+        spaceAfterMarker = true;
+      } else if (state.src.charCodeAt(pos) === 0x09 /* tab */) {
+        spaceAfterMarker = true;
+
+        if ((state.bsCount[nextLine] + offset) % 4 === 3) {
+          // '  >\t  test '
+          //       ^ -- position start of line here (tab has width===1)
+          pos++;
+          initial++;
+          offset++;
+          adjustTab = false;
+        } else {
+          // ' >\t  test '
+          //    ^ -- position start of line here + shift bsCount slightly
+          //         to make extra space appear
+          adjustTab = true;
+        }
+      } else {
+        spaceAfterMarker = false;
+      }
+
       oldBMarks.push(state.bMarks[nextLine]);
       state.bMarks[nextLine] = pos;
 
@@ -106,7 +177,7 @@ module.exports = function blockquote(state, startLine, endLine, silent) {
 
         if (isSpace(ch)) {
           if (ch === 0x09) {
-            offset += 4 - offset % 4;
+            offset += 4 - (offset + state.bsCount[nextLine] + (adjustTab ? 1 : 0)) % 4;
           } else {
             offset++;
           }
@@ -119,6 +190,9 @@ module.exports = function blockquote(state, startLine, endLine, silent) {
 
       lastLineEmpty = pos >= max;
 
+      oldBSCount.push(state.bsCount[nextLine]);
+      state.bsCount[nextLine] = state.sCount[nextLine] + 1 + (spaceAfterMarker ? 1 : 0);
+
       oldSCount.push(state.sCount[nextLine]);
       state.sCount[nextLine] = offset - initial;
 
@@ -141,6 +215,7 @@ module.exports = function blockquote(state, startLine, endLine, silent) {
     if (terminate) { break; }
 
     oldBMarks.push(state.bMarks[nextLine]);
+    oldBSCount.push(state.bsCount[nextLine]);
     oldTShift.push(state.tShift[nextLine]);
     oldSCount.push(state.sCount[nextLine]);
 
@@ -167,6 +242,7 @@ module.exports = function blockquote(state, startLine, endLine, silent) {
     state.bMarks[i + startLine] = oldBMarks[i];
     state.tShift[i + startLine] = oldTShift[i];
     state.sCount[i + startLine] = oldSCount[i];
+    state.bsCount[i + startLine] = oldBSCount[i];
   }
   state.blkIndent = oldIndent;
 

lib/rules_block/list.js

@@ -209,7 +209,7 @@ module.exports = function list(state, startLine, endLine, silent) {
 
       if (isSpace(ch)) {
         if (ch === 0x09) {
-          offset += 4 - offset % 4;
+          offset += 4 - (offset + state.bsCount[nextLine]) % 4;
         } else {
           offset++;
         }

lib/rules_block/state_block.js

@@ -27,6 +27,18 @@ function StateBlock(src, md, env, tokens) {
   this.tShift = [];  // offsets of the first non-space characters (tabs not expanded)
   this.sCount = [];  // indents for each line (tabs expanded)
 
+  // An amount of virtual spaces (tabs expanded) between beginning
+  // of each line (bMarks) and real beginning of that line.
+  //
+  // It exists only as a hack because blockquotes override bMarks
+  // losing information in the process.
+  //
+  // It's used only when expanding tabs, you can think about it as
+  // an initial tab length, e.g. bsCount=21 applied to string `\t123`
+  // means first tab should be expanded to 4-21%4 === 3 spaces.
+  //
+  this.bsCount = [];
+
   // block parser variables
   this.blkIndent  = 0; // required block content indent
                        // (for example, if we are in list)
@@ -73,6 +85,7 @@ function StateBlock(src, md, env, tokens) {
       this.eMarks.push(pos);
       this.tShift.push(indent);
       this.sCount.push(offset);
+      this.bsCount.push(0);
 
       indent_found = false;
       indent = 0;
@@ -86,6 +99,7 @@ function StateBlock(src, md, env, tokens) {
   this.eMarks.push(s.length);
   this.tShift.push(0);
   this.sCount.push(0);
+  this.bsCount.push(0);
 
   this.lineMax = this.bMarks.length - 1; // don't count last fake line
 }
@@ -183,7 +197,7 @@ StateBlock.prototype.getLines = function getLines(begin, end, indent, keepLastLF
 
       if (isSpace(ch)) {
         if (ch === 0x09) {
-          lineIndent += 4 - lineIndent % 4;
+          lineIndent += 4 - (lineIndent + this.bsCount[line]) % 4;
         } else {
           lineIndent++;
         }

test/fixtures/markdown-it/commonmark_extras.txt

@@ -288,12 +288,88 @@ test
 
 Coverage. Tabs in blockquotes.
 .
-   >	 foo
+>		test
-   > 	 bar
+
+ >		test
+
+  >		test
+
+> ---
+>		test
+
+ > ---
+ >		test
+
+  > ---
+  >		test
+
+>			test
+
+ >			test
+
+  >			test
+
+> ---
+>			test
+
+ > ---
+ >			test
+
+  > ---
+  >			test
 .
 <blockquote>
-<pre><code> foo
+<pre><code>  test
- bar
+</code></pre>
+</blockquote>
+<blockquote>
+<pre><code> test
+</code></pre>
+</blockquote>
+<blockquote>
+<pre><code>test
+</code></pre>
+</blockquote>
+<blockquote>
+<hr>
+<pre><code>  test
+</code></pre>
+</blockquote>
+<blockquote>
+<hr>
+<pre><code> test
+</code></pre>
+</blockquote>
+<blockquote>
+<hr>
+<pre><code>test
+</code></pre>
+</blockquote>
+<blockquote>
+<pre><code>  	test
+</code></pre>
+</blockquote>
+<blockquote>
+<pre><code> 	test
+</code></pre>
+</blockquote>
+<blockquote>
+<pre><code>	test
+</code></pre>
+</blockquote>
+<blockquote>
+<hr>
+<pre><code>  	test
+</code></pre>
+</blockquote>
+<blockquote>
+<hr>
+<pre><code> 	test
+</code></pre>
+</blockquote>
+<blockquote>
+<hr>
+<pre><code>	test
 </code></pre>
 </blockquote>
 .