Fixed transistor renderer preview behavior

[9larsons]

ref https://linear.app/ghost/issue/NY-1150/
ref https://linear.app/ghost/issue/NY-1151/

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• ghost/core/core/server/api/endpoints/utils/serializers/output/utils/post-gating.js

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Walkthrough

Preview rendering now replaces Transistor iframe blocks with a static placeholder via an exported forPost in the post-gating serializer. The Transistor node renderer was refactored to emit an iframe with a data-src and a noscript fallback (instead of the previous static placeholder), optionally include a ctx (site UUID) query parameter in embed URLs, and append a runtime script that detects an ancestor background color and sets the iframe src with that color as a query parameter. Unit tests were updated to assert iframe/embed URL, noscript fallback, background-detection script, and ctx propagation.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: fixing transistor renderer preview behavior, which aligns with the changeset modifications to preview mode handling in post-gating and transistor renderer.
Description check	✅ Passed	The description references two related Linear issues (NY-1150 and NY-1151) that provide context for the changes, which is related to the changeset.

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[coderabbitai]

🧹 Nitpick comments (1)

ghost/core/core/server/services/koenig/node-renderers/transistor-renderer.js (1)

16-22: Consider using CSS instead of deprecated frameborder attribute.

The frameborder attribute is deprecated in HTML5. While it still works for backwards compatibility, you could use CSS border: none on the iframe for a more standards-compliant approach.

♻️ Proposed refactor using inline style

 function setIframeAttributes(iframe) {
     iframe.setAttribute('width', '100%');
     iframe.setAttribute('height', '370');
-    iframe.setAttribute('frameborder', 'no');
     iframe.setAttribute('scrolling', 'no');
     iframe.setAttribute('seamless', '');
+    iframe.setAttribute('style', 'border: none;');
 }

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@ghost/core/core/server/services/koenig/node-renderers/transistor-renderer.js`
around lines 16 - 22, In setIframeAttributes, stop using the deprecated
frameborder attribute and instead apply CSS to the iframe (e.g., set
style.border = 'none' or append to iframe.style.cssText) so the iframe has no
border; update the function (referencing setIframeAttributes and the iframe
parameter) to remove iframe.setAttribute('frameborder', 'no') and add the
equivalent style-based rule, and consider using CSS for scrolling behavior too
rather than the scrolling attribute.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In
`@ghost/core/core/server/services/koenig/node-renderers/transistor-renderer.js`:
- Around line 16-22: In setIframeAttributes, stop using the deprecated
frameborder attribute and instead apply CSS to the iframe (e.g., set
style.border = 'none' or append to iframe.style.cssText) so the iframe has no
border; update the function (referencing setIframeAttributes and the iframe
parameter) to remove iframe.setAttribute('frameborder', 'no') and add the
equivalent style-based rule, and consider using CSS for scrolling behavior too
rather than the scrolling attribute.

---

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Configuration used: Path: .coderabbit.yaml

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📥 Commits

Reviewing files that changed from the base of the PR and between 257ee2b and b821d15.

📒 Files selected for processing (3)

• ghost/core/core/server/api/endpoints/utils/serializers/output/utils/post-gating.js
• ghost/core/core/server/services/koenig/node-renderers/transistor-renderer.js
• ghost/core/test/unit/server/services/koenig/node-renderers/transistor-renderer.test.js

[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In
`@ghost/core/core/server/api/endpoints/utils/serializers/output/utils/post-gating.js`:
- Around line 121-126: The preview branch that replaces attrs.html when
frame.isPreview uses _buildTransistorPlaceholder() but does not refresh derived
fields, leaving attrs.plaintext and attrs.excerpt stale; after you replace
attrs.html, regenerate the derived text fields the same way other HTML-rewrite
branches do (i.e. invoke the module/helper used elsewhere to compute plaintext
and excerpt from the new attrs.html and assign the results back to
attrs.plaintext and attrs.excerpt) so preview responses return up-to-date
derived values.
- Around line 122-124: The current regex in the attrs.html replacement for
Transistor embeds is too strict about tag adjacency and should allow arbitrary
whitespace/newlines between </iframe>, <script> and <noscript> (e.g. use \s* or
[\s\S]*? between those serialized tags) so jsdom-serialized markup matches;
after performing the replacement (the call that assigns attrs.html =
attrs.html.replace(..., _buildTransistorPlaceholder())), call
_updateTextAttrs(attrs) just like the gated block at line 109 to refresh
attrs.plaintext and attrs.excerpt so derived text fields stay in sync with the
modified HTML.

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📥 Commits

Reviewing files that changed from the base of the PR and between b821d15 and 2e9461b.

📒 Files selected for processing (1)

• ghost/core/core/server/api/endpoints/utils/serializers/output/utils/post-gating.js