feat: register heading tags as server-side block elements (#173)

ep_headings2 already registers h1-h4 + code as block elements in
the editor (aceRegisterBlockElements). It did NOT register them
on the server-side content collector (ccRegisterBlockElements),
so any HTML import path treated those tags as inline -- and
adjacent <h1>/<h2>/<code> blocks merged into a single pad line.

Fix: re-export the new ccRegisterBlockElements function from
ep_plugin_helpers' lineAttribute factory (added in
ether/ep_plugin_helpers#14) and wire it up via ep.json. This
treats h1-h4 + code as block elements on the import side too,
matching their editor behavior.

Bumps the ep_plugin_helpers minimum to ^0.5.2 (the version with
the new export).

Test added covers the regression: a pad with adjacent <h1> and
<h2> (no separator) survives a setHTML/getHTML round-trip with
each heading on its own line and no merged 'AlphaBeta' content.

Refs ether/etherpad#7568 -- this is the missing piece for the
DOCX/HTML round-trip story landing in core.

Author: JohnMcLear

ep.json

@@ -16,6 +16,7 @@
         "eejsBlock_editbarMenuLeft": "ep_headings2/index",
         "collectContentPre": "ep_headings2/static/js/shared",
         "collectContentPost": "ep_headings2/static/js/shared",
+        "ccRegisterBlockElements": "ep_headings2/static/js/shared",
         "getLineHTMLForExport": "ep_headings2/index",
         "stylesForExport" : "ep_headings2/index"
       }

package.json

@@ -34,7 +34,7 @@
     "url": "https://github.com/ether/ep_headings2/issues"
   },
   "dependencies": {
-    "ep_plugin_helpers": "^0.3.2"
+    "ep_plugin_helpers": "^0.5.2"
   },
   "devDependencies": {
     "eslint": "^8.57.1",

static/js/shared.js

@@ -8,3 +8,4 @@ const headings = lineAttribute({attr: 'heading', tags});
 
 exports.collectContentPre = headings.collectContentPre;
 exports.collectContentPost = headings.collectContentPost;
+exports.ccRegisterBlockElements = headings.ccRegisterBlockElements;

static/tests/backend/specs/exportHTML.ts

@@ -121,4 +121,35 @@ describe('ep_headings2 - export headings to HTML', function () {
       }
     });
   });
+
+  context('when pad has adjacent <h1> and <h2> with no separator', function () {
+    // Regression for ether/etherpad#7568 round-trip. Without server-side
+    // ccRegisterBlockElements registered for the heading tags,
+    // contentcollector treats <h1>/<h2> as inline and adjacent ones
+    // merge into a single pad line.
+    before(async function () {
+      html = () => buildHTML('<h1>Alpha</h1><h2>Beta</h2>');
+    });
+
+    it('keeps each heading on its own line', function (done) {
+      const expected = /<h1>\s*Alpha\s*<\/h1>[\s\S]*<h2>\s*Beta\s*<\/h2>/;
+      generateJWTToken().then((token) => {
+        agent.get(getHTMLEndPointFor(padID))
+            .set('Authorization', token)
+            .end((err, res) => {
+              if (err) return done(err);
+              const out = res.body.data.html;
+              if (out.search(expected) === -1) {
+                return done(new Error(
+                    `Adjacent headings merged or missing in: ${out}`));
+              }
+              if (out.search(/AlphaBeta/) !== -1) {
+                return done(new Error(
+                    `Headings merged into one line: ${out}`));
+              }
+              done();
+            });
+      }).catch(done);
+    });
+  });
 });