From 92b610bb3a0d8b3716cd6efd755fd187e588a434 Mon Sep 17 00:00:00 2001
From: ph1p <me@ph1p.dev>
Date: Tue, 22 Nov 2022 18:27:33 +0100
Subject: [PATCH] feature: add new option to disable anchors in headlines

---
 markdown.d.ts    |  3 +++
 src/common.h     |  7 ++++---
 src/fmt_html.c   |  2 +-
 src/md.js        | 11 ++++++++---
 test/issue22.js  | 30 ++++++++++++++++++++++++++++++
 test/testutil.js |  4 ++--
 6 files changed, 48 insertions(+), 9 deletions(-)
 create mode 100644 test/issue22.js

diff --git a/markdown.d.ts b/markdown.d.ts
index 638fd82..ef151b1 100644
--- a/markdown.d.ts
+++ b/markdown.d.ts
@@ -16,6 +16,9 @@ export interface ParseOptions {
   /** Select output format. Defaults to "html" */
   format? : "html" | "xhtml"
 
+  /** Disable anchor tag in headlines. Defaults to `false` */
+  disableHeadlineAnchors? : boolean
+
   /**
    * bytes=true causes parse() to return the result as a Uint8Array instead of a string.
    *
diff --git a/src/common.h b/src/common.h
index 5a0c8f3..b75901e 100644
--- a/src/common.h
+++ b/src/common.h
@@ -63,9 +63,10 @@ typedef int32_t  i32;
 
 // these should be in sync with "OutputFlags" in md.js
 typedef enum OutputFlags {
-  OutputFlagHTML       = 1 << 0,
-  OutputFlagXHTML      = 1 << 1,
-  OutputFlagAllowJSURI = 1 << 2, // allow "javascript:" URIs in links
+  OutputFlagHTML                   = 1 << 0,
+  OutputFlagXHTML                  = 1 << 1,
+  OutputFlagAllowJSURI             = 1 << 2, // allow "javascript:" URIs in links
+  OutputFlagDisableHeadlineAnchors = 1 << 3,
 } OutputFlags;
 
 typedef int(*JSTextFilterFun)(
diff --git a/src/fmt_html.c b/src/fmt_html.c
index 6894ef4..25f5a90 100644
--- a/src/fmt_html.c
+++ b/src/fmt_html.c
@@ -323,7 +323,7 @@ static int enter_block_callback(MD_BLOCKTYPE type, void* detail, void* userdata)
     case MD_BLOCK_H:
     {
       render_literal(r, head[((MD_BLOCK_H_DETAIL*)detail)->level - 1]);
-      r->addanchor = 1;
+      r->addanchor = !(r->flags & OutputFlagDisableHeadlineAnchors);
       break;
     }
     case MD_BLOCK_CODE:  render_open_code_block(r, (const MD_BLOCK_CODE_DETAIL*) detail); break;
diff --git a/src/md.js b/src/md.js
index c85a52f..ae900a0 100644
--- a/src/md.js
+++ b/src/md.js
@@ -43,9 +43,10 @@ export const ParseFlags = {
 
 // these should be in sync with "OutputFlags" in common.h
 const OutputFlags = {
-  HTML:       1 << 0, // Output HTML
-  XHTML:      1 << 1, // Output XHTML (only has effect with HTML flag set)
-  AllowJSURI: 1 << 2, // Allow "javascript:" URIs
+  HTML:                   1 << 0, // Output HTML
+  XHTML:                  1 << 1, // Output XHTML (only has effect with HTML flag set)
+  AllowJSURI:             1 << 2, // Allow "javascript:" URIs
+  DisableHeadlineAnchors: 1 << 3, // Disable anchor tag in headlines.
 }
 
 
@@ -59,6 +60,10 @@ export function parse(source, options) {
 
   let outputFlags = options.allowJSURIs ? OutputFlags.AllowJSURI : 0
 
+  if(options.disableHeadlineAnchors)  {
+    outputFlags |= OutputFlags.DisableHeadlineAnchors;
+  };
+
   switch (options.format) {
     case "xhtml":
       outputFlags |= OutputFlags.HTML | OutputFlags.XHTML
diff --git a/test/issue22.js b/test/issue22.js
new file mode 100644
index 0000000..62f4aa6
--- /dev/null
+++ b/test/issue22.js
@@ -0,0 +1,30 @@
+// https://github.com/rsms/markdown-wasm/issues/22
+const { checkHTMLResult, exit } = require('./testutil');
+
+checkHTMLResult('DISABLE_HEADLINE_ANCHOR', `# Test1
+## Test2
+### Test3
+#### Test4
+`, `<h1>Test1</h1>
+<h2>Test2</h2>
+<h3>Test3</h3>
+<h4>Test4</h4>\n`, {
+  disableHeadlineAnchors: true,
+});
+
+checkHTMLResult(
+  'ENABLE_HEADLINE_ANCHOR',
+  `# Test1
+## Test2
+### Test3
+#### Test4`,
+  `<h1><a id="test1" class="anchor" aria-hidden="true" href="#test1"></a>Test1</h1>
+<h2><a id="test2" class="anchor" aria-hidden="true" href="#test2"></a>Test2</h2>
+<h3><a id="test3" class="anchor" aria-hidden="true" href="#test3"></a>Test3</h3>
+<h4><a id="test4" class="anchor" aria-hidden="true" href="#test4"></a>Test4</h4>\n`,
+  {
+    disableHeadlineAnchors: false,
+  }
+);
+
+exit();
diff --git a/test/testutil.js b/test/testutil.js
index f1efa9e..7cde8f9 100644
--- a/test/testutil.js
+++ b/test/testutil.js
@@ -10,14 +10,14 @@ const wave = "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"
 exports.numFailures = 0
 
 
-exports.checkHTMLResult = function check(name, inputData, expectedOutputData) {
+exports.checkHTMLResult = function check(name, inputData, expectedOutputData, options = {}) {
   if (typeof inputData == "string") {
     inputData = Buffer.from(inputData, "utf8")
   }
   if (typeof expectedOutputData == "string") {
     expectedOutputData = Buffer.from(expectedOutputData, "utf8")
   }
-  const actual = Buffer.from(md.parse(inputData, { asMemoryView: true }))
+  const actual = Buffer.from(md.parse(inputData, { asMemoryView: true, ...options }))
   if (expectedOutputData.compare(actual) == 0) {
     log(`${name} OK`)
     return true