WM Posts Blocks

A small WordPress plugin that registers two Gutenberg blocks — a dynamic Posts Grid and a companion Posts Filter — that stay in sync anywhere on the page, and seeds a complete demo environment automatically on activation.

Built for the WordPress Web Development Team Lead technical assessment.

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Table of contents

1. What it does
2. Quick start
3. Architecture overview
4. The key decision: inter-block communication
5. How the filtering logic works (OR / AND)
6. Demo content seeding
7. Project structure
8. Trade-offs & known limitations
9. Coding standards

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What it does

Requirement	Where it's implemented
Posts Grid — dynamic, not hardcoded	src/posts-grid/render.php + includes/class-posts-query.php
Title, featured image, excerpt	shape_post() in class-posts-query.php
Inspector Controls: columns (2/3/4) & posts per page	src/posts-grid/edit.js
Pagination as an inner block of the grid	src/posts-grid-pagination/ (restricted via parent in block.json)
Posts Filter — category + tag, multi-select	src/posts-filter/render.php
OR within a filter, AND across filters	Posts_Query::get_posts() (tax_query)
Blocks sync without nesting	Shared Interactivity API store, src/store.js
Seed ≥10 posts, ≥3 categories, multiple tags, featured images, demo page	includes/class-seeder.php
Unique prefix on slug / post type / taxonomies	wmpb_ everywhere (class-content-model.php)
Admin settings page (columns, fields shown, brand colour, card style, image ratio, excerpt length)	includes/class-settings.php
Generated gradient featured images (no network on activation)	Seeder::create_featured_image()
Card chips + meta (category chip, date · reading time, tag row)	Posts_Query::shape_post()
Result count, Clear-filters, loading bar	src/posts-grid/render.php + src/store.js

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Quick start

Option A — zero-config with wp-env (recommended)

Requires Docker and Node.js 18+.

# 1. Install build tooling
npm install

# 2. Compile the blocks (creates the /build folder)
npm run build

# 3. Boot a throwaway WordPress with this plugin already active
npm run env:start

Then open http://localhost:8888/wp-admin (user admin, password password). On activation the plugin creates everything, so visit the page titled “WM Posts Blocks Demo” on the front end and try the filters + pagination.

To stop / reset:

npm run env:stop     # stop containers
npm run env:clean    # wipe the environment entirely

Option B — install into an existing WordPress site

npm install
npm run build        # the /build folder is required at runtime

Then copy the whole wm-posts-blocks folder into wp-content/plugins/ (or zip it and upload via Plugins → Add New → Upload) and click Activate.

Important: the plugin runs from the compiled /build directory, so npm run build must be run before activating. If you received a .zip, the build is already included.

Development

npm start            # rebuild on save (watch mode)

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Architecture overview

                       ┌─────────────────────────────────────────┐
                       │            wmpb/posts (shared store)      │
   Posts Filter ──────▶│  state.selectedCategories / selectedTags  │◀────── Pagination
   (checkboxes)        │  state.posts / page / totalPages          │        (prev / next)
                       └───────────────────┬───────────────────────┘
                                           │ actions.refresh()
                                           ▼
                          GET /wp-json/wmpb/v1/posts?...   (REST_Controller)
                                           │
                                           ▼
                              Posts_Query::get_posts()      (one WP_Query, OR/AND)
                                           │
                                           ▼
                       state.posts updated ─▶ data-wp-each re-renders the grid

PHP side (small, single-responsibility classes under includes/):

• Content_Model — registers the wmpb_post CPT and the wmpb_category / wmpb_tag taxonomies.
• Posts_Query — the only place posts are queried and shaped. Used by both the server render and the REST endpoint, so the filtering rules can't drift.
• REST_Controller — exposes GET /wmpb/v1/posts, delegates to Posts_Query.
• Blocks — registers the three compiled blocks from /build.
• Seeder — activation seeding (terms, posts, images, demo page); idempotent.
• Plugin — wires every class to its WordPress hooks (the only “glue” file).

JS side (src/): three blocks, each with an editor component (edit.js), a server render (render.php) and a tiny front-end module (view.js) that imports the single shared store in src/store.js.

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The key decision: inter-block communication

“The filter and grid blocks must stay in sync without being nested inside each other. Choose the approach you think is most appropriate.”

I chose the WordPress Interactivity API with a single shared store (namespace wmpb/posts).

Why

Every interactive element in both blocks declares data-wp-interactive="wmpb/posts". The Interactivity API resolves directives by namespace, not by DOM position, so all of them read and write the same global store no matter where they sit on the page. That is precisely the problem the brief describes — independent blocks that must share state — and it is the exact scenario the Interactivity API was designed for since WordPress 6.5.

Concretely:

• The filter writes state.selectedCategories / state.selectedTags.
• That triggers actions.refresh(), which fetches the matching posts.
• The result is written to state.posts, and the grid's data-wp-each template re-renders automatically.
• The pagination inner block writes state.page and calls the same refresh().

There is no custom event bus, no nesting, and no manual DOM querying — the reactive store is the single source of truth.

Alternatives I considered (and why I didn't pick them)

Approach	Why not
Custom DOM events (document.dispatchEvent)	Works, but it's an ad-hoc pub/sub I'd have to invent, document and guard against typos. The Interactivity API gives the same decoupling with reactive state for free.
@wordpress/data (Redux-like) store	Great in the editor, but it's not the idiomatic tool for front-end interactivity and would mean shipping a heavier runtime to render server-side content.
Nesting the grid inside the filter	Explicitly disallowed by the brief, and it couples two concerns that should be placeable independently.

Initial render: server-seeded state, single render path

The grid uses one rendering path: a data-wp-each template (in render.php) that renders one card per item in state.posts. Crucially, the first page of posts is seeded into the store server-side with wp_interactivity_state(), so the data ships inline in the initial HTML and the grid populates the moment the runtime hydrates — no extra fetch, no loading flash for the first view. The same template then handles every filter and pagination change.

I deliberately do not also print the cards as static <article> HTML: data-wp-each appends its rendered output rather than reconciling against existing sibling nodes, so doing both renders every card twice. (I verified this in a real browser — see "Trade-offs" below.)

Trade-off: because the cards are rendered client-side, a JavaScript-disabled client sees the post data only in the inline JSON, not as visible cards. A fully no-JS / crawler-friendly version would render server HTML and swap it with the Interactivity Router region pattern (data-wp-router-region) that the core Query Loop block uses for enhanced pagination — a sensible next step, but heavier than this brief needs.

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Admin settings page

Settings → WM Posts Blocks is a single control centre (class-settings.php, built on the WordPress Settings API with a sanitiser for every field):

• Layout — default columns per row, posts per page.
• Content — which fields show (image / excerpt / meta) and excerpt length.
• Style — brand accent colour, card style (elevated / bordered / minimal), image aspect ratio.

The model is intentionally easy to explain:

• Per-instance layout (columns, posts-per-page) lives on the grid block, where editors expect it. Each grid can also choose “Global default” (stored as 0) to follow the site setting — so a team gets one consistent look while any page can still override.
• Site-wide presentation & content lives in the settings page. render.php reads it into CSS custom properties (--wmpb-accent, --wmpb-ratio) and a card style class, and toggles which fields the card template outputs. One change re-themes every grid on the site with no code edits.

How the filtering logic works (OR / AND)

The rule — OR within a filter type, AND across filter types — maps cleanly onto a single WP_Query tax_query (includes/class-posts-query.php):

$tax_query = array( 'relation' => 'AND' );          // AND across types

if ( $categories ) {
    $tax_query[] = array(
        'taxonomy' => 'wmpb_category',
        'terms'    => $categories,
        'operator' => 'IN',                          // OR within categories
    );
}
if ( $tags ) {
    $tax_query[] = array(
        'taxonomy' => 'wmpb_tag',
        'terms'    => $tags,
        'operator' => 'IN',                          // OR within tags
    );
}

• operator => 'IN' → “match any of these terms” = OR within a type.
• relation => 'AND' → both clauses must pass = AND across types.

So selecting Engineering, Design + Tutorial returns posts that are (Engineering OR Design) AND Tutorial. Doing it in the database (rather than filtering in PHP/JS) keeps pagination counts correct.

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Demo content seeding

On activation (includes/class-seeder.php), and only once (guarded by the wmpb_seeded option so re-activation never duplicates):

• 4 categories and 6 tags are created.

• 12 posts are inserted with deliberately overlapping category/tag assignments, so filter combinations produce meaningful, non-empty results.

• Each post gets a diagonal-gradient featured image generated locally with PHP's GD extension (drawn small, upscaled smoothly, with soft overlay circles) — no external HTTP request, which would be fragile on locked-down hosts. Body length varies per post so the cards show a range of reading times.

• A demo page is created with both blocks already placed:

  <!-- wp:wmpb/posts-filter /-->
  <!-- wp:wmpb/posts-grid {"columns":3,"perPage":6} -->
      <!-- wp:wmpb/posts-grid-pagination /-->
  <!-- /wp:wmpb/posts-grid -->

Deleting the plugin from wp-admin runs uninstall.php, which removes every post, attachment, term, the demo page and the options — leaving the site clean.

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Project structure

wm-posts-blocks/
├── wm-posts-blocks.php          # Plugin header, constants, lifecycle hooks
├── uninstall.php                # Full teardown on delete
├── includes/
│   ├── class-plugin.php         # Hook wiring
│   ├── class-content-model.php  # CPT + taxonomies (wmpb_ prefix)
│   ├── class-settings.php       # Admin settings page (Settings API)
│   ├── class-posts-query.php    # Shared query + OR/AND logic + card shaping
│   ├── class-rest-controller.php# GET /wmpb/v1/posts
│   ├── class-blocks.php         # register_block_type() x3
│   └── class-seeder.php         # Activation seeding
├── src/
│   ├── store.js                 # The shared Interactivity store (the “brain”)
│   ├── posts-grid/              # Block 1 (block.json, edit, render.php, view, scss)
│   ├── posts-grid-pagination/   # Inner block (parent: posts-grid)
│   └── posts-filter/            # Block 2
├── build/                       # Compiled output (generated by npm run build)
├── .wp-env.json                 # One-command local WordPress
└── package.json

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Trade-offs & known limitations

• One filter + one grid per page. The shared store is global to the wmpb/posts namespace, which is the simplest correct model for the brief. Supporting multiple independent grid/filter pairs on a single page would mean scoping state by an instance ID — a deliberate next step, not needed here.
• The store is duplicated into each block's view bundle. It lives once in source (src/store.js) but @wordpress/scripts inlines it into each view module. Re-declaring the same namespace just merges, so this is correct; sharing a single runtime module would shave a few KB at the cost of a more complex build.
• Generated placeholder images are solid-colour JPEGs (intentionally, to avoid network calls on activation). Swapping in real imagery is a one-line change in Seeder::create_featured_image().
• No automated tests. For a plugin this size I prioritised clear structure and a strong manual demo; the Posts_Query class is deliberately pure and isolated so it would be the natural first unit-test target.

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Coding standards

• PHP follows the WordPress Coding Standards (tabs, Yoda-free readable conditionals, full DocBlocks, escaping on all output, sanitising on all input). Lint with composer/phpcs if desired.
• JS/CSS follow @wordpress/scripts defaults: npm run lint:js, npm run lint:css, npm run format.
• Modern PHP namespaces (WMPB\) are used instead of long prefixed function names — a deliberate choice for a small, class-based plugin.