Re-implement MD038 to handle multi-line spans better and rely less on RegExp.

lib/shared.js

@@ -239,6 +239,69 @@ module.exports.forEachHeading = function forEachHeading(params, callback) {
   });
 };
 
+// Calls the provided function for each inline code span's content
+module.exports.forEachInlineCodeSpan =
+  function forEachInlineCodeSpan(input, callback) {
+    let currentLine = 0;
+    let currentColumn = 0;
+    let index = 0;
+    while (index < input.length) {
+      let startIndex = -1;
+      let startLine = -1;
+      let startColumn = -1;
+      let tickCount = 0;
+      let currentTicks = 0;
+      // Deliberate <= so trailing 0 completes the last span (ex: "text `code`")
+      for (; index <= input.length; index++) {
+        const char = input[index];
+        if (char === "`") {
+          // Count backticks at start or end of code span
+          currentTicks++;
+          if ((startIndex === -1) || (startColumn === -1)) {
+            startIndex = index + 1;
+          }
+        } else {
+          if ((startIndex >= 0) &&
+            (startColumn >= 0) &&
+            (tickCount === currentTicks)) {
+            // Found end backticks; invoke callback for code span
+            callback(
+              input.substring(startIndex, index - currentTicks),
+              startLine, startColumn, tickCount);
+            startIndex = -1;
+            startColumn = -1;
+          } else if ((startIndex >= 0) && (startColumn === -1)) {
+            // Found start backticks
+            tickCount = currentTicks;
+            startLine = currentLine;
+            startColumn = currentColumn;
+          }
+          // Not in backticks
+          currentTicks = 0;
+        }
+        if (char === "\n") {
+          // On next line
+          currentLine++;
+          currentColumn = 0;
+        } else if ((char === "\\") &&
+          ((startIndex === -1) || (startColumn === -1))) {
+          // Escape character outside code, skip next
+          index++;
+          currentColumn += 2;
+        } else {
+          // On next column
+          currentColumn++;
+        }
+      }
+      if (startIndex >= 0) {
+        // Restart loop after unmatched start backticks (ex: "`text``code``")
+        index = startIndex;
+        currentLine = startLine;
+        currentColumn = startColumn;
+      }
+    }
+  };
+
 // Returns (nested) lists as a flat array (in order)
 module.exports.flattenLists = function flattenLists() {
   return tokenCache.flattenedLists;