Fix null dereference in helpers.getPreferredLineEnding when running in browser (platform unknown, process object not available) and input string does not contain line endings.

demo/markdownlint-browser.js

@@ -25,7 +25,7 @@ module.exports = webpackEmptyContext;
 /*!*****************************!*\
   !*** ../helpers/helpers.js ***!
   \*****************************/
-/***/ ((module) => {
+/***/ ((module, __unused_webpack_exports, __webpack_require__) => {
 
 "use strict";
 // @ts-check
@@ -774,6 +774,17 @@ function emphasisMarkersInContent(params) {
     return byLine;
 }
 module.exports.emphasisMarkersInContent = emphasisMarkersInContent;
+/**
+ * Gets the platform identifier from a string or process-like object.
+ *
+ * @param {string} platform Platform identifier (process.platform).
+ * @param {Object} process Node.js process object.
+ * @returns {string} Platform identifier.
+ */
+function getPlatformIdentifier(platform, process) {
+    return (platform || (process && process.platform) || "unknown");
+}
+module.exports.getPlatformIdentifier = getPlatformIdentifier;
 /**
  * Gets the most common line ending, falling back to the platform default.
  *
@@ -803,7 +814,10 @@ function getPreferredLineEnding(input, platform) {
     var preferredLineEnding = null;
     if (!cr && !lf && !crlf) {
         preferredLineEnding =
-            ((platform || process.platform) === "win32") ? "\r\n" : "\n";
+            // eslint-disable-next-line node/prefer-global/process
+            (getPlatformIdentifier(platform, __webpack_require__(/*! process */ "?4c74")) === "win32") ?
+                "\r\n" :
+                "\n";
     }
     else if ((lf >= crlf) && (lf >= cr)) {
         preferredLineEnding = "\n";
@@ -1013,6 +1027,16 @@ module.exports = markdownit;
 
 /***/ }),
 
+/***/ "?4c74":
+/*!*************************!*\
+  !*** process (ignored) ***!
+  \*************************/
+/***/ (() => {
+
+/* (ignored) */
+
+/***/ }),
+
 /***/ "?ec0a":
 /*!********************!*\
   !*** fs (ignored) ***!

demo/webpack.config.js

@@ -45,6 +45,7 @@ function config(options) {
       "fallback": {
         "fs": false,
         "path": false,
+        "process": false,
         "util": false
       }
     }

helpers/helpers.js

@@ -789,6 +789,18 @@ function emphasisMarkersInContent(params) {
 }
 module.exports.emphasisMarkersInContent = emphasisMarkersInContent;
 
+/**
+ * Gets the platform identifier from a string or process-like object.
+ *
+ * @param {string} platform Platform identifier (process.platform).
+ * @param {Object} process Node.js process object.
+ * @returns {string} Platform identifier.
+ */
+function getPlatformIdentifier(platform, process) {
+  return (platform || (process && process.platform) || "unknown");
+}
+module.exports.getPlatformIdentifier = getPlatformIdentifier;
+
 /**
  * Gets the most common line ending, falling back to the platform default.
  *
@@ -818,7 +830,10 @@ function getPreferredLineEnding(input, platform) {
   let preferredLineEnding = null;
   if (!cr && !lf && !crlf) {
     preferredLineEnding =
-      ((platform || process.platform) === "win32") ? "\r\n" : "\n";
+      // eslint-disable-next-line node/prefer-global/process
+      (getPlatformIdentifier(platform, require("process")) === "win32") ?
+        "\r\n" :
+        "\n";
   } else if ((lf >= crlf) && (lf >= cr)) {
     preferredLineEnding = "\n";
   } else if (crlf >= cr) {

test/markdownlint-test-helpers.js

@@ -390,6 +390,14 @@ test("forEachInlineCodeSpan", (t) => {
   });
 });
 
+test("getPlatformIdentifier", (t) => {
+  t.plan(4);
+  t.is(helpers.getPlatformIdentifier("custom", process), "custom");
+  t.is(helpers.getPlatformIdentifier("custom", null), "custom");
+  t.is(helpers.getPlatformIdentifier(null, process), process.platform);
+  t.is(helpers.getPlatformIdentifier(null, null), "unknown");
+});
+
 test("getPreferredLineEnding", (t) => {
   t.plan(19);
   const testCases = [