Allow nested begin/end in bare blocks

microsoft/vscode#141905

Author: mjbvz

index.js

@@ -203,14 +203,13 @@ function bare_math_block(state, start, end, silent) {
     const endRe = /^\\end/;
 
     if (!beginRe.test(firstLine)) { return false; }
-    
+
     if (silent) { return true; }
 
+    let nestingCount = 0;
     let next;
     for (next = start; !found;) {
-
         next++;
-
         if (next >= end) { break; }
 
         pos = state.bMarks[next] + state.tShift[next];
@@ -221,10 +220,15 @@ function bare_math_block(state, start, end, silent) {
             break;
         }
         const line = state.src.slice(pos, max);
-        if (endRe.test(line)) {
-            const lastPos = max;
-            lastLine = state.src.slice(pos, lastPos);
-            found = true;
+        if (beginRe.test(line)) {
+            ++nestingCount;
+        } else if (endRe.test(line)) {
+            --nestingCount;
+            if (nestingCount < 0) {
+                const lastPos = max;
+                lastLine = state.src.slice(pos, lastPos);
+                found = true;
+            }
         }
     }
 

test/fixtures/bare.txt

@@ -29,3 +29,24 @@ end
 \end{equation}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1.2000000000000002em;vertical-align:-0.35000000000000003em;"></span><span class="mtable"><span class="col-align-c"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8500000000000001em;"><span style="top:-3.01em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">2</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.35000000000000003em;"><span></span></span></span></span></span></span></span><span class="tag"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8500000000000001em;"><span style="top:-2.8499999999999996em;"><span class="pstrut" style="height:2.84em;"></span><span class="eqn-num"></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.35000000000000003em;"><span></span></span></span></span></span></span></span></span></p>
 <p>end</p>
 .
+
+Bare block with multiple begin/ends
+.
+start
+\begin{equation}
+\begin{split}
+a = b \\
+c = c
+\end{split}
+\end{equation}
+end
+.
+<p>start</p>
+<p class="katex-block"><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mtable rowspacing="0.1600em" columnspacing="1em"><mtr><mtd class ="mtr-glue"></mtd><mtd><mstyle scriptlevel="0" displaystyle="true"><mtable rowspacing="0.2500em" columnalign="right" columnspacing=""><mtr><mtd><mstyle scriptlevel="0" displaystyle="true"><mrow><mi>a</mi><mo>=</mo><mi>b</mi></mrow></mstyle></mtd></mtr><mtr><mtd><mstyle scriptlevel="0" displaystyle="true"><mrow><mi>c</mi><mo>=</mo><mi>c</mi></mrow></mstyle></mtd></mtr></mtable></mstyle></mtd><mtd class ="mtr-glue"></mtd><mtd class ="mml-eqn-num"></mtd></mtr></mtable><annotation encoding="application/x-tex">\begin{equation}
+\begin{split}
+a = b \\
+c = c
+\end{split}
+\end{equation}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:3.0000000000000004em;vertical-align:-1.2500000000000002em;"></span><span class="mtable"><span class="col-align-c"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.7500000000000002em;"><span style="top:-3.75em;"><span class="pstrut" style="height:3.75em;"></span><span class="mord"><span class="mord"><span class="mtable"><span class="col-align-r"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.7500000000000002em;"><span style="top:-3.91em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord mathnormal">a</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mord mathnormal">b</span></span></span><span style="top:-2.41em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord mathnormal">c</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mord mathnormal">c</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:1.2500000000000002em;"><span></span></span></span></span></span></span></span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:1.2500000000000002em;"><span></span></span></span></span></span></span></span><span class="tag"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.7500000000000002em;"><span style="top:-3.75em;"><span class="pstrut" style="height:3.75em;"></span><span class="eqn-num"></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:1.2500000000000002em;"><span></span></span></span></span></span></span></span></span></p>
+<p>end</p>
+.