Templates REST API: prevent fatal error when a null template reaches prepare_item_for_response

[ramonjd]

What?

Prevents an uncaught fatal error in the templates REST controller:

Attempt to assign property "content" on null

Why?

Core's WP_REST_Templates_Controller::update_item() passes its get_block_template() refetches to prepare_item_for_response() without checking them, both after writing an update (line 423, where a production trace shows the fatal firing) and on its revert-to-theme path, which force-deletes the template's post first (line 380). When a refetch returns null, the method fatals reading $item->content. The WP 7.2 compat controller now answers a null template with a rest_template_not_found (404) error response instead of crashing. Needs backporting to core.

How does the test prove the guard?

test_prepare_item_for_response_with_null_template calls prepare_item_for_response( null, … ) directly — the exact condition that fatals on trunk — and asserts a WP_Error with code rest_template_not_found comes back. Without the guard, the call fatals and the test run aborts, so the test can only pass through the guard.

Testing Instructions

The revert path is the easiest way to reach the fatal:

1. Create a template that exists only in the database: POST /wp/v2/templates with { "slug": "db-only", "title": "T", "content": "" }.
2. Send PUT /wp/v2/templates/<theme>//db-only with { "source": "theme" }.
3. On trunk this fatals with the error above; with this branch it returns 404 rest_template_not_found.

Summary by CodeRabbit

• Bug Fixes

  • Fixed an issue in WordPress 7.2 where requesting a nonexistent template through the REST API could trigger a fatal error.
  • Nonexistent templates now return a proper “not found” error response.
  • Improved REST API compatibility for templates and template parts on WordPress 7.2.

• Documentation

  • Added links to the related WordPress and Gutenberg pull requests.

[github-actions]

🤖 PR meta 🤖

⚡ Performance

Show the results

Client side metrics exclude the server response time.

front-end-block-theme

Metric	638399c	trunk	% Change
timeToFirstByte	46.75 ms +9.52% -6.84%	46.1 ms +11.06% -2.6%	1.41%
largestContentfulPaint	76 ms +0% -2.63%	72 ms +11.11% -0%	5.56%
lcpMinusTtfb	29.9 ms +11.2% -18.23%	26.7 ms +14.23% -5.06%	11.99%
wpBeforeTemplate	24.21 ms +12.1% -11.15%	22.09 ms +20.33% -1.86%	9.6%
wpTemplate	19.2 ms +4.64% -4.06%	20.62 ms +1.79% -6.84%	-6.89%
wpTotal	43.55 ms +7.83% -7.26%	42.85 ms +10.2% -2.75%	1.63%
wpMemoryUsage	7.54 MB +0% -0%	7.50 MB +0% -0%	0.47%
wpDbQueries	17 +0% -0%	17 +0% -0%	0%

front-end-classic-theme

Metric	638399c	trunk	% Change
timeToFirstByte	37.85 ms +14% -4.76%	31.1 ms +13.18% -3.38%	21.7%
largestContentfulPaint	76 ms +5.26% -5.26%	68 ms +2.94% -5.88%	11.76%
lcpMinusTtfb	36.4 ms +6.59% -1.1%	33.55 ms +4.62% -3.13%	8.49%
wpBeforeTemplate	19.27 ms +20.13% -1.4%	19.4 ms +18.4% -3.14%	-0.67%
wpTemplate	14.54 ms +4.68% -1.93%	9.06 ms +6.95% -2.98%	60.49%
wpTotal	34.66 ms +14.77% -3.81%	28.6 ms +13.36% -3.11%	21.19%
wpMemoryUsage	6.16 MB +0% -0%	5.38 MB +0% -0%	14.42%
wpDbQueries	14 +0% -0%	10 +0% -0%	40%

media-processing

Metric	638399c	trunk	% Change
mediaProcessingJpeg	322.26 ms +0.36% -0.81%	324.12 ms +0.45% -1.13%	-0.57%
mediaProcessingAvif	4958.41 ms +0.36% -0.13%	4948.04 ms +0.19% -0.21%	0.21%
mediaProcessingJpegToAvif	3547.64 ms +0.25% -0.47%	3545.78 ms +0.27% -0.37%	0.05%

media-upload

Metric	638399c	trunk	% Change
jpegUploadProcessing	1395.83 ms +1.15% -0.12%	1396.53 ms +0.97% -1.14%	-0.05%
pngUploadProcessing	187.93 ms +5.33% -6.36%	176.25 ms +4.91% -3.7%	6.63%
largeJpegUploadProcessing	1406.65 ms +1.39% -0.87%	1402.14 ms +0.65% -0.41%	0.32%
multipleImageUploadProcessing	1479.02 ms +0.95% -1.62%	1452.49 ms +3.53% -0.36%	1.83%

post-editor

Metric	638399c	trunk	% Change
serverResponse	447.99 ms +6.59% -8.09%	468.24 ms +2.04% -6.88%	-4.32%
firstPaint	198.47 ms +26.59% -14.27%	216.67 ms +9.96% -5.12%	-8.4%
domContentLoaded	1289.06 ms +0.94% -1.82%	1285.43 ms +1.69% -1.17%	0.28%
loaded	1290.35 ms +0.94% -1.81%	1286.71 ms +1.69% -1.17%	0.28%
firstContentfulPaint	431.03 ms +1.47% -16.54%	436.69 ms +1.81% -5.02%	-1.3%
firstBlock	3474.16 ms +0.48% -1.88%	3480.9 ms +0.98% -1.35%	-0.19%
type	20.81 ms +13.02% -18.6%	21.53 ms +12.68% -17.97%	-3.34%
typeWithoutInspector	21.35 ms +10.77% -16.02%	21.89 ms +10.19% -13.25%	-2.47%
typeWithTopToolbar	24.49 ms +6.29% -11.84%	23.25 ms +12.82% -14.92%	5.33%
typeContainer	9.52 ms +6.41% -6.2%	9.65 ms +2.28% -13.37%	-1.35%
focus	83.42 ms +10.57% -15.2%	77.7 ms +6.25% -8.93%	7.36%
firstFocus	180.23 ms +0% -0%	168.69 ms +0% -0%	6.84%
selectAll	592.78 ms +0.05% -2.95%	575.05 ms +1.24% -1.64%	3.08%
listViewOpen	67.34 ms +15.01% -7.89%	65.64 ms +12.58% -6.37%	2.59%
inserterOpen	23.38 ms +6.37% -5.43%	23.22 ms +9.09% -10.72%	0.69%
inserterHover	4.05 ms +10.62% -7.65%	3.48 ms +10.63% -6.61%	16.38%
inserterSearch	7.85 ms +14.9% -7.13%	8.57 ms +14% -5.6%	-8.4%
loadPatterns	640.97 ms +10.66% -1.27%	638.77 ms +3.77% -4.21%	0.34%
wpTotal	436.83 ms +6.84% -8.27%	456.92 ms +2.09% -7.41%	-4.4%
wpMemoryUsage	13.13 MB +0% -0%	13.10 MB +0% -0%	0.22%
wpDbQueries	54 +0% -1.85%	54 +0% -1.85%	0%

site-editor

Metric	638399c	trunk	% Change
serverResponse	328.66 ms +3.18% -8.2%	330.36 ms +1.35% -1.4%	-0.51%
firstPaint	189.95 ms +13.97% -16.5%	179.17 ms +20.49% -7.12%	6.02%
domContentLoaded	1053.21 ms +1.29% -1.13%	1045.5 ms +0.73% -0.55%	0.74%
loaded	1054.18 ms +1.29% -1.13%	1046.5 ms +0.72% -0.54%	0.73%
firstContentfulPaint	329.46 ms +1.81% -1.64%	331.49 ms +4.24% -1.79%	-0.61%
firstBlock	3303.96 ms +0.41% -0.49%	3267.9 ms +0.18% -0.15%	1.1%
type	15.34 ms +14.02% -11.41%	15.83 ms +16.55% -17.25%	-3.1%
navigate	87.99 ms +25.03% -14.27%	79.61 ms +18.59% -5.67%	10.53%
loadPatterns	1048.81 ms +3.82% -2.99%	1030.02 ms +23.03% -5.74%	1.82%
loadPages	1135.66 ms +9.87% -3.41%	1304.39 ms +3.94% -3.36%	-12.94%
wpTotal	320.31 ms +3.26% -8.34%	321.99 ms +1.47% -1.44%	-0.52%
wpMemoryUsage	12.09 MB +0% -0%	12.05 MB +0% -0%	0.31%
wpDbQueries	43.5 +1.15% -1.15%	44 +0% -2.27%	-1.14%

_{ee768e1 Run}

🏁 Flaky tests

Show the failures

Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

should (visually) render any HTML in Post Editor's post title field when in Visual editing mode in /test/e2e/specs/editor/various/post-title.spec.js, passed after 1 failed attempt.

Error: apiRequestContext.fetch: socket hang up
Call log:
  - → POST http://localhost:8889/wp-json/wp/v2/posts
    - user-agent: Playwright/1.62.1 (x64; ubuntu 24.04) node/20.20 CI/1
    - accept: */*
    - accept-encoding: gzip,deflate,br
    - X-WP-Nonce: a4d774683a
    - content-type: application/json
    - content-length: 134
    - cookie: wordpress_test_cookie=WP%20Cookie%20check; wordpress_logged_in_23778236db82f19306f247e20a353a99=admin%7C1788662626%7C86P9UEz6CR4Lz2i6UcJgRb8wryHtgWcKj7w7aRfKPOJ%7Cf01ae75434af8aaafa21c0440c63f5cd7f2d4e21c7f1c4b66627f2d003cecdca; wp-settings-time-1=1788490494

    at RequestUtils.rest (/home/runner/work/gutenberg/gutenberg/packages/e2e-test-utils-playwright/src/request-utils/rest.ts:112:39)
    at RequestUtils.createRecord (/home/runner/work/gutenberg/gutenberg/packages/e2e-test-utils-playwright/src/request-utils/records.ts:20:14)
    at RequestUtils.createPost (/home/runner/work/gutenberg/gutenberg/packages/e2e-test-utils-playwright/src/request-utils/posts.ts:65:14)
    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/editor/various/post-title.spec.js:67:46

should allow a block with styles to be converted to a reusable block in /test/e2e/specs/editor/various/patterns.spec.js, passed after 1 failed attempt.

Error: apiRequestContext.fetch: socket hang up
Call log:
  - → GET http://localhost:8889/wp-json/wp/v2/posts?per_page=100&status=publish%2Cfuture%2Cdraft%2Cpending%2Cprivate%2Ctrash
    - user-agent: Playwright/1.62.1 (x64; ubuntu 24.04) node/20.20 CI/1
    - accept: */*
    - accept-encoding: gzip,deflate,br
    - X-WP-Nonce: 3902cbfd5f
    - cookie: wordpress_test_cookie=WP%20Cookie%20check; wordpress_logged_in_23778236db82f19306f247e20a353a99=admin%7C1788662579%7CLwx7TdEhi7Twl3h3JOspKXpAxLc7WrUoE9IpqDXSVWH%7C34656d964dd1be124966a0121989aa9f0c73bf00af3c510785898b3b862849b3; wp-settings-time-1=1788490301

    at RequestUtils.rest (/home/runner/work/gutenberg/gutenberg/packages/e2e-test-utils-playwright/src/request-utils/rest.ts:112:39)
    at RequestUtils.deleteAllPosts (/home/runner/work/gutenberg/gutenberg/packages/e2e-test-utils-playwright/src/request-utils/posts.ts:30:27)
    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/editor/various/patterns.spec.js:774:22

_{ee768e1 Run}

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No actionable comments were generated in the recent review. 🎉

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Configuration used: defaults

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Plan: Team

Run ID: 3fb00a69-3073-43aa-90ec-f58752433499

📥 Commits

Reviewing files that changed from the base of the PR and between e07550a and ee768e1.

📒 Files selected for processing (1)

• lib/compat/wordpress-7.2/class-gutenberg-rest-templates-controller-7-2.php

🚧 Files skipped from review as they are similar to previous changes (1)

• lib/compat/wordpress-7.2/class-gutenberg-rest-templates-controller-7-2.php

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---

📝 Walkthrough

Walkthrough

The change adds WordPress 7.2 REST controller compatibility for templates and template parts. It returns a 404 error for null templates, loads the compatibility controller, registers it for both post types, and adds a regression test.

Changes

Template REST compatibility

Layer / File(s)	Summary
Controller null-template handling lib/compat/wordpress-7.2/class-gutenberg-rest-templates-controller-7-2.php, phpunit/class-gutenberg-rest-templates-controller-test.php	The WordPress 7.2 controller returns rest_template_not_found for null templates. The regression test verifies the returned WP_Error.
REST controller loading and wiring lib/load.php, lib/compat/wordpress-7.2/rest-api.php, backport-changelog/7.2/13375.md	The compatibility controller is loaded and assigned to wp_template and wp_template_part. The changelog records the related pull request references.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to ee768

The compatibility controller change handles missing templates with a REST 404 response, with no remaining concrete merge-readiness risk identified.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically summarizes the main change: preventing a fatal error when a null template reaches prepare_item_for_response().
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 4 files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/prevent-null-template-fatal

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If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: ramonjd <ramonopoly@git.wordpress.org>
Co-authored-by: aaronrobertshaw <aaronrobertshaw@git.wordpress.org>

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[Copilot]

🟢 Approval recommended

The guard, controller registration, regression coverage, and Core backport are consistent and complete.

Pull request overview

Adds a WordPress 7.2 compatibility guard that returns a 404 REST error instead of fatally dereferencing a null template.

Changes:

• Adds and registers the guarded templates controller.
• Covers null-template handling with a PHPUnit regression test.
• Records the corresponding Core backport.

File summaries

File	Description
phpunit/class-gutenberg-rest-templates-controller-test.php	Tests null-template handling.
lib/load.php	Loads the compatibility controller.
lib/compat/wordpress-7.2/rest-api.php	Registers it for templates and template parts.
lib/compat/wordpress-7.2/class-gutenberg-rest-templates-controller-7-2.php	Returns a 404 error for null templates.
backport-changelog/7.2/13375.md	Links the Core backport.

Review details

• Files reviewed: 5/5 changed files
• Comments generated: 0
• Review effort level: Balanced

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[aaronrobertshaw]

Thanks for this @ramonjd 👍

It's looking good to me. You can probably ignore the minor nits below.

I had one question about create_item also having a second refetch that isn't guard against null but I couldn't come up with a natural way to trigger it short of a very malformed plugin. So I think this is the minimal fix here.

On that note, getting it in now to prevent a reproducible fatal is a win.

[ramonjd]

Thanks for the quick review @aaronrobertshaw

I'll tidy up those comments.