Preserve backslash escapes and add roundtrip tests

src/processor.ts

@@ -426,6 +426,24 @@ const keepMarkerPlugin = (option: { doc: string }) => {
   return transformer;
 };
 
+const restoreEscapes = (option: { doc: string }) => {
+  const { doc } = option;
+  const transformer = (ast: HastRoot) => {
+    visitParents(
+      ast,
+      (node) => node.type === "text" && !!node.position,
+      (node: any, _parent: any) => {
+        const { start, end } = node.position;
+        const original = doc.slice(start.offset, end.offset);
+        if (original.includes("\\") && original.replace(/\\/g, "") === node.value) {
+          node.value = original;
+        }
+      },
+    );
+  };
+  return transformer;
+};
+
 const postProcessHtmlMarker = (option: { doc: string }) => {
   const { doc } = option;
   const allowHtmlTags = ["summary"];
@@ -852,6 +870,7 @@ class MdProcessor extends Processor {
 
     const hast = unified()
       .use(keepMarkerPlugin, { doc: newDoc })
+      .use(restoreEscapes, { doc: newDoc })
       .use(prepareMdast, { contentsAvoidMarkdown })
       .use(remark2rehype, {
         passThrough: ["definition"],

test/fixtures/inline-styles.md

@@ -0,0 +1,17 @@
+**bold with asterisks**
+
+__bold with underscores__
+
+<strong>bold with html</strong>
+
+*italic with asterisks*
+
+_italic with underscores_
+
+<em>italic with html</em>
+
+**bold *and italic* together**
+
+<strong>html bold with <em>html italic</em> inside</strong>
+
+Text with \#escaped hash and \*escaped asterisk\* here

test/index.spec.ts

@@ -24,23 +24,17 @@ function processAndCompare(filename: string) {
   console.log(filename);
 }
 
-function processAndCompareWithExpected(filename: string) {
-  const inDoc = eol.lf(
+function processAndCompareRoundtrip(filename: string) {
+  const input = eol.lf(
     fs.readFileSync(path.join("test", "fixtures", filename), {
       encoding: "utf-8",
     }),
   );
-  const inDocExpected = eol.lf(
-    fs.readFileSync(path.join("test", "expected", filename), {
-      encoding: "utf-8",
-    }),
-  );
 
-  const doc = processor.parse(inDoc);
-  const outDoc = processor.stringify(doc);
+  const doc = processor.parse(input);
+  const output = eol.lf(processor.stringify(doc));
 
-  assert.equal(outDoc, inDocExpected);
-  console.log(filename);
+  assert.equal(output, input);
 }
 
 describe("MdProcessorTest", function () {
@@ -72,4 +66,19 @@ describe("MdProcessorTest", function () {
       processAndCompare(filename);
     });
   });
+
+  const roundtripFiles = [
+    "link.md",
+    "images.md",
+    "images-html.md",
+    "break.md",
+    "description-list.md",
+    "inline-styles.md",
+  ];
+
+  roundtripFiles.forEach((filename) => {
+    it(`should roundtrip ${filename} exactly`, function () {
+      processAndCompareRoundtrip(filename);
+    });
+  });
 });