ADFA-5405: Let templates reference each other

[davidschachterADFA]

Templates in the Templates table can now reference each other, so an author can build a page out of a layout, a nav partial and a page body instead of one self-contained file. ADFA-5405

Why it didn't work

The engine was built with Pebble's StringLoader, which treats the name it is handed as the template body, and it was handed each template's source as its name. So every cross-reference resolved to itself: {% include "nav.peb" %} asked the loader for nav.peb, got those eight characters back as a template, and the page rendered the literal text. No exception, no log line. page.peb and nav.peb work around this today by defining local macros rather than including each other.

The change

DatabaseTemplateLoader resolves a name against Templates.name, so extends, include, import and embed all work. Content rows still name their outermost template by id; render resolves that id to a name and the engine loads and caches from there — which drops our own compiled-template map, since the engine already caches by name. Name is the better key anyway: a partial shared by many pages is compiled once. Both caches are dropped on a database swap, the engine's included.

No schema change and no new dependency: the database already holds four named templates, and Pebble 4.1.1 already exposes the loader interface.

A reference to a name with no row now fails the request naming the template, rather than rendering the name as text.

Review by commit

1. Add a Pebble loader that reads the Templates table — the loader and its unit tests, not yet wired up.
2. Load templates by name, so they can reference each other — switches the engine over, plus docs/documentation-database.md.
3. Render the bookshelf by name, dropping its id cache — the bookshelf endpoint took the name directly, which removed its cached template id, the lock and generation tag around it, and the pre-serve refresh that existed only to make that check land on the right side of a swap.

Verification

637 unit tests green across :common and :app; Spotless clean. Four new tests cover include, extends, a missing reference, and a named render; three existing template tests were updated for the id-to-name lookup.

On a Pixel 6 Pro, against a debug documentation.db carrying three cross-referencing templates:

Request	Result
page that extends a layout and includes a nav partial	200 — <main>Hello Kotlin! [nav:Kotlin]</main>
page referencing a name with no row	500 — Template 'e2e-nowhere' not found in the database
existing single-template Kotlin page	200, unchanged
/pr/bs (bookshelf, now rendered by name)	200, unchanged

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📒 Files selected for processing (4)

• common/src/main/java/com/itsaky/androidide/documentation/DatabaseTemplateLoader.kt
• common/src/main/java/com/itsaky/androidide/documentation/DocumentationContentSource.kt
• common/src/test/java/com/itsaky/androidide/documentation/DocumentationContentSourceTest.kt
• docs/documentation-database.md

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📝 Summary

• Templates can reference other templates by name with Pebble extends, include, import, and embed.
• Replaced StringLoader with DatabaseTemplateLoader.
• Added name-based template caching and template/tag cache invalidation after database changes.
• Missing template references now fail with diagnostics that identify the template name.
• Template reference cycles now fail with IllegalStateException.
• Limited rendered output to 16 million characters.
• Updated the bookshelf endpoint to render templates by name.
• Optimized loader existence checks to avoid copying template content.
• Updated documentation and tests for template inheritance, inclusion, missing references, named rendering, cycles, and bookshelf rendering.
• No schema or dependency changes.
• Verification passed: 641 unit tests and Spotless checks.
• Risk: Template references must match Templates.name exactly.
• Risk: Cache invalidation must run after database changes to prevent stale templates.
• Risk: Templates that require more than 16 million output characters now fail.

Walkthrough

The change replaces template-ID compilation with name-based database resolution. Pebble loads referenced templates from SQLite by exact name. WebServer renders the bookshelf template by name and forwards missing-template diagnostics.

Changes

Named Template Rendering

Layer / File(s)	Summary
Database template loader and tests common/src/main/java/com/itsaky/androidide/documentation/DatabaseTemplateLoader.kt, common/src/test/java/com/itsaky/androidide/documentation/DatabaseTemplateLoaderTest.kt	DatabaseTemplateLoader resolves exact Templates.name values, returns UTF-8 content, and throws LoaderException for missing templates or unavailable databases.
Content source named rendering common/src/main/java/com/itsaky/androidide/documentation/DocumentationContentSource.kt, common/src/test/java/com/itsaky/androidide/documentation/DocumentationContentSourceTest.kt	DocumentationContentSource uses the database loader, caches names and compiled templates by name, bounds rendered output, invalidates Pebble template and tag caches, and reports named rendering errors. Tests cover includes, inheritance, missing references, cycles, cache behavior, parse errors, and context validation.
Bookshelf endpoint integration app/src/main/java/com/itsaky/androidide/localWebServer/WebServer.kt, app/src/test/java/com/itsaky/androidide/localWebServer/WebServerTest.kt	The bookshelf endpoint calls renderNamedTemplate("bookshelf", ...). The endpoint no longer performs template-ID lookup or per-request cache invalidation. Error responses include loader diagnostics.
Template resolution documentation docs/documentation-database.md	The documentation distinguishes outer template IDs from name-based inter-template references and documents failures for missing names.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to cdaf2

Templates can now reference named database templates while preserving diagnostics, bounded rendering, and cache invalidation behavior. No current merge-blocking risk remains.

Sequence Diagram(s)

sequenceDiagram
  participant WebServer
  participant DocumentationContentSource
  participant DatabaseTemplateLoader
  participant SQLiteDatabase
  WebServer->>DocumentationContentSource: renderNamedTemplate("bookshelf", contextJson, "/bookshelf")
  DocumentationContentSource->>DatabaseTemplateLoader: resolve template by name
  DatabaseTemplateLoader->>SQLiteDatabase: query Templates by exact name
  SQLiteDatabase-->>DatabaseTemplateLoader: return template content or no row
  DatabaseTemplateLoader-->>DocumentationContentSource: return reader or LoaderException
  DocumentationContentSource-->>WebServer: return rendered bytes or IllegalStateException

Loading

Poem

I’m a rabbit with templates tucked tight,
Names hop through the database at night.
The bookshelf blooms with a direct little call,
Includes and layouts now answer them all,
Pebble resolves each reference right.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 55.56% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 45 functions across 6 files. (1 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: enabling templates to reference each other. It is concise and specific.
Description check	✅ Passed	The description directly explains the template-reference changes, implementation, behavior, testing, and related issue.
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.

Full details: Docstring Coverage

Explanation

Docstring coverage is 55.56% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 45 functions across 6 files. (1 skipped: 1 unsupported.)

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Actionable comments posted: 1

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Inline comments:
In `@app/src/main/java/com/itsaky/androidide/localWebServer/WebServer.kt`:
- Line 854: Update handleBsEndpoint’s renderNamedTemplate error path to pass the
caught LoaderException message, using e.message ?: "" as the sendError details
instead of only the generic bookshelf error text.

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📒 Files selected for processing (7)

• app/src/main/java/com/itsaky/androidide/localWebServer/WebServer.kt
• app/src/test/java/com/itsaky/androidide/localWebServer/WebServerTest.kt
• common/src/main/java/com/itsaky/androidide/documentation/DatabaseTemplateLoader.kt
• common/src/main/java/com/itsaky/androidide/documentation/DocumentationContentSource.kt
• common/src/test/java/com/itsaky/androidide/documentation/DatabaseTemplateLoaderTest.kt
• common/src/test/java/com/itsaky/androidide/documentation/DocumentationContentSourceTest.kt
• docs/documentation-database.md

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[davidschachterADFA]

Ran an xhigh review over this PR. Five findings were real and are fixed in 6e6d865; five I'm closing as invalid, with the checks below.

Fixed

#	Finding	Fix
1	The regression test I added in ccc34a1 was vacuous: it asserted the 500 body contains("bookshelf"), but the generic fallback "Error generating bookshelf HTML." contains "bookshelf" too, so it passed with or without the fix it was named for.	Asserts the loader's own sentence now. Verified it fails against the reverted fix: Expected the loader's diagnostic, got: ... Error generating bookshelf HTML.
2	PebbleException formats getMessage() as "<text> (<file>:<line>)" and the loader throws with both null, so /pr/bs answered Template 'bookshelf' not found in the database (?:?).	Translated to getPebbleMessage() in DocumentationContentSource, not in WebServer — that keeps Pebble out of both transports, which is the ADFA-5176 layering. Test asserts the exact message and the absence of (?:?).
3	A reference cycle is reachable now that a reference resolves to another row — Pebble has no cycle detection and recurses until the stack ends. StackOverflowError is an Error, so every catch (Exception) on the serving path passes it through and the client gets a closed socket with no status line.	Raised as an IllegalStateException naming the template. Worth noting the listener already survived this: the accept loop catches Throwable and its comment already anticipates "a pathological template a StackOverflowError". So this is about the response, not the server's life.
4	clearTemplateCache() invalidated templateCache but not tagCache, so a template's {% cache %} blocks would outlive the database swap the method exists to handle.	tagCache.invalidateAll() added.
5	renderTemplate(templateId, …) has no caller after e362822 moved the only one to renderNamedTemplate, and no test uses it.	Deleted. generation and refreshDatabase() are kept — three tests read them as the observable that a swap happened — but their KDoc now says outright that they have no production reader, rather than implying a caller to hunt for.

Not fixed, with reasons

Three findings rest on the claim that Templates has no constraints. The DDL is id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT NOT NULL, content BLOB NOT NULL, UNIQUE('name'), and I checked what SQLite does with the quoted form rather than assume:

sqlite> CREATE TABLE T (id INTEGER PRIMARY KEY, name TEXT NOT NULL, content BLOB NOT NULL, UNIQUE('name'));
sqlite> INSERT INTO T (name,content) VALUES ('a', x'00');
sqlite> INSERT INTO T (name,content) VALUES ('a', x'01');
Error: UNIQUE constraint failed: T.name
sqlite> INSERT INTO T (name,content) VALUES (NULL, x'00');
Error: NOT NULL constraint failed: T.name

SQLite reads the quoted string as a column name, so the constraint is live. That disposes of:

• NULL/empty name breaks the page — NOT NULL rejects it. (Empty string would need a deliberate '' insert; SELECT count(*) FROM Templates WHERE name IS NULL OR name = '' OR content IS NULL is 0 on the shipped database.)
• Duplicate names render silently, since the removed isCursorOneRow guard is gone — UNIQUE('name') rejects the second row. The count > 1 check kept on the id lookup is likewise belt-and-braces over a PRIMARY KEY; it predates this PR and I left it alone.
• NULL content throws a bare NPE — BLOB NOT NULL rejects it.

Two more:

• A database with no Templates table throws a raw SQLiteException — pre-existing and unreachable. Such a database has no Content.templateId column either, so CONTENT_QUERY fails before any template lookup. Only resourceExists throwing rather than returning false is new, and nothing reaches it.
• getReader/resourceExists duplicate the query plumbing — two four-line methods; a shared helper costs about as much as it saves. Happy to change it if you'd rather.

Two comment tidies also went in: the test-class KDoc describing generation as what callers use to drop per-database caches (6e6d865), and the stale "serveRequest applies any pending swap" note, which described a call deleted in e362822 (59d7328).

640 unit tests green across :common and :app, Spotless clean.

[davidschachterADFA]

Second xhigh pass. Five fixed in cdaf2da, five closed with reasons.

Fixed

#	Finding	Fix
1	The getPebbleMessage() change in 6e6d865 strips PebbleException's "(<file>:<line>)" suffix from every exception, not just the loader's null/null ones — so a syntax error in a template says what is wrong but not which template or line.	My regression, and the sharper version of the finding I acted on last round. Now conditional on the exception carrying neither. Verified against ParserException(Throwable, String, int, String) in the jar, which does carry both. New test fails without the fix with Unexpected token "EXECUTE_END" and no template name.
2	The cycle guard catches StackOverflowError, but maxRenderedSize is at its -1 default, so unbounded output exhausts the heap and OutOfMemoryError escapes.	maxRenderedSize(16 MB chars). Confirmed in the bytecode that LimitedSizeWriter throws PebbleException(null, "Tried to write more than %d chars.") — null file and line, so it flows through fix 1 cleanly and comes out as a 500.
3	clearTemplateCache() mutates three caches outside databaseLock while renders hold the read lock.	Takes the write lock now; reentrant, so switchToDatabase keeps working.
4	resourceExists runs SELECT content, copying the whole blob to answer a boolean.	Separate SELECT 1 … LIMIT 1.
5	generation/refreshDatabase() documented as unused rather than marked.	@VisibleForTesting.

Two corrections to the finding text, since both matter for whether the fix is right:

• The cycle framing in [ADFA-320] - add Permissions Screen Test #2 is not quite right. A reference cycle recurses, so it reaches the end of the stack before it can grow the output — the StackOverflowError guard does cover it. What maxRenderedSize covers is a runaway that stays at one frame, a loop being the obvious case. Both are now bounded, but by different mechanisms, and the code comment says so rather than repeating the cycle framing.
• [ADFA-320] - add Permissions Screen Test #2 has no test. Exercising the limit means rendering 16M chars. The constant is headroom over the largest context this database holds (171 KB of compressed JSON), not a measured ceiling on rendered output — tighten it if the real maximum is known.

Not fixed

The three Templates constraint findings are the same three from the first review, and they are still wrong. Both reviews read the bare column list in docs/documentation-database.md and concluded there is no UNIQUE on name. The DDL is name TEXT NOT NULL, content BLOB NOT NULL, UNIQUE('name'), and SQLite resolves the single-quoted form to the column:

sqlite> INSERT INTO T (name,content) VALUES ('a', x'00');
sqlite> INSERT INTO T (name,content) VALUES ('a', x'01');
Error: UNIQUE constraint failed: T.name
sqlite> INSERT INTO T (name,content) VALUES (NULL, x'00');
Error: NOT NULL constraint failed: T.name

Two independent reviews reaching the same wrong conclusion from the same doc is a defect in the doc, not in the reviews — so cdaf2da puts the DDL and that UNIQUE('name') trap into documentation-database.md. That should stop it recurring.

One correction to my previous reply: I wrote that the null/empty/duplicate count is "0 on the shipped database". I queried a local ~/Downloads/documentation.db. assets/documentation.db is gitignored and fetched at build time, so nothing in the repo pins the shipped content — the constraint argument above stands on the DDL, which does not depend on which copy you look at.

Remaining two:

• /pr/bs echoes any exception message, leaking SQL and the database path on loopback:6174 — partly valid, and I left it. The same endpoint's inner catch already did e.message ?: "" before this PR, and the content path does the same with lookup.cause.message, so narrowing only the outer catch changes little. Worth its own ticket across all three sites if you want the endpoint to stop echoing internals; say the word and I will file it.
• Interceptor declines a Failed lookup, so WebServer re-renders and pays the failure twice — real, but the decline-on-Failed contract is ADFA-5176's, and changing it moves error responsibility between the two transports. Out of scope here.

Also declined: keying the loader on an id-shaped "#7" to drop the id→name hop. It saves one cached lookup per template and puts a magic prefix into a namespace of author-chosen names.

641 unit tests green across :common and :app, Spotless clean.

[davidschachterADFA]

Filed ADFA-5468 for the error-echo point rather than fixing it here.

Checking the siblings turned up four sites, not the three I described above — WebServer.kt lines 591 (content path), 625 (sendContent failure), 860 (realHandleBsEndpoint inner catch) and 780 (the outer catch this PR touched). Three predate ADFA-5405. Narrowing one of four while the rest keep echoing would look like a fix without being one, so it wants a single change with a decision behind it: echo only the messages this code raises deliberately — the Template 'x' not found in the database class — and send fixed text otherwise.

The ticket flags that line 780's echo is intentional and pinned by a regression test here, so whoever picks it up keeps that behavior rather than reverting it.