[Bugfix] Fix the backticks bug (#26)

* [Bugfix] Fix the backticks bug

* Add test for inline backtick parse

SR-15415

Author: Kyle-Ye

api_test/main.c

@@ -1126,6 +1126,26 @@ static void source_pos_inlines(test_batch_runner *runner) {
     free(xml);
     cmark_node_free(doc);
   }
+  {
+    static const char markdown[] =
+      "` It is one backtick\n"
+      "`` They are two backticks\n";
+
+    cmark_node *doc = cmark_parse_document(markdown, sizeof(markdown) - 1, CMARK_OPT_DEFAULT);
+    char *xml = cmark_render_xml(doc, CMARK_OPT_DEFAULT | CMARK_OPT_SOURCEPOS);
+    STR_EQ(runner, xml, "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
+                        "<!DOCTYPE document SYSTEM \"CommonMark.dtd\">\n"
+                        "<document sourcepos=\"1:1-2:25\" xmlns=\"http://commonmark.org/xml/1.0\">\n"
+                        "  <paragraph sourcepos=\"1:1-2:25\">\n"
+                        "    <text sourcepos=\"1:1-1:20\" xml:space=\"preserve\">` It is one backtick</text>\n"
+                        "    <softbreak />\n"
+                        "    <text sourcepos=\"2:1-2:25\" xml:space=\"preserve\">`` They are two backticks</text>\n"
+                        "  </paragraph>\n"
+                        "</document>\n",
+                        "sourcepos are as expected");
+    free(xml);
+    cmark_node_free(doc);
+  }
 }
 
 static void ref_source_pos(test_batch_runner *runner) {

src/inlines.c

@@ -373,13 +373,14 @@ static void S_normalize_code(cmark_strbuf *s) {
 // Parse backtick code section or raw backticks, return an inline.
 // Assumes that the subject has a backtick at the current position.
 static cmark_node *handle_backticks(subject *subj, int options) {
+  bufsize_t initpos = subj->pos;
   cmark_chunk openticks = take_while(subj, isbacktick);
   bufsize_t startpos = subj->pos;
   bufsize_t endpos = scan_to_closing_backticks(subj, openticks.len);
 
   if (endpos == 0) {      // not found
     subj->pos = startpos; // rewind
-    return make_str(subj, subj->pos, subj->pos, openticks);
+    return make_str(subj, initpos, initpos + openticks.len - 1, openticks);
   } else {
     cmark_strbuf buf = CMARK_BUF_INIT(subj->mem);