Fix enabling and using the extension on MSSQL

controller/acp_controller.php

@@ -1928,8 +1928,10 @@ public function update_category_data(&$category_data, $copy_perm_from_id): array
 				$row = $this->db->sql_fetchrow($result);
 				$this->db->sql_freeresult($result);
 
-				$category_data_sql['left_id'] = $row['right_id'] + 1;
-				$category_data_sql['right_id'] = $row['right_id'] + 2;
+				// MAX() of an empty table is NULL, which MSSQL's driver
+				// returns as an empty string
+				$category_data_sql['left_id'] = (int) $row['right_id'] + 1;
+				$category_data_sql['right_id'] = (int) $row['right_id'] + 2;
 			}
 
 			$sql = 'INSERT INTO ' . $this->categories_table . ' ' . $this->db->sql_build_array('INSERT', $category_data_sql);
@@ -2094,7 +2096,8 @@ protected function move_category($from_id, $to_id): array
 			$row = $this->db->sql_fetchrow($result);
 			$this->db->sql_freeresult($result);
 
-			$diff = '+ ' . ($row['right_id'] - $from_data['left_id'] + 1);
+			// (int): MAX() over no rows is NULL, an empty string from MSSQL's driver
+			$diff = '+ ' . ((int) $row['right_id'] - (int) $from_data['left_id'] + 1);
 		}
 
 		$sql = 'UPDATE ' . $this->categories_table . '

controller/article.php

@@ -236,7 +236,8 @@ public function show(): \Symfony\Component\HttpFoundation\Response
 		if ($comment_topic_id)
 		{
 			$count = -1;
-			$sql = 'SELECT DISTINCT p.poster_id, p.post_time, p.post_subject, p.post_text, p.bbcode_uid, p.bbcode_bitfield, u.user_id, u.username
+			// No DISTINCT: one user per post, and MSSQL cannot compare post_text
+			$sql = 'SELECT p.poster_id, p.post_time, p.post_subject, p.post_text, p.bbcode_uid, p.bbcode_bitfield, u.user_id, u.username
 				FROM ' . POSTS_TABLE . ' p, ' . USERS_TABLE . ' u
 				WHERE p.topic_id = ' . (int) $comment_topic_id . '
 				AND (p.poster_id = u.user_id)

controller/posting.php

@@ -261,7 +261,9 @@ public function post_article(): \Symfony\Component\HttpFoundation\Response
 		$delete_allowed = $edit_allowed = $article_author_id = false;
 		if ($mode === 'edit' || $mode === 'delete')
 		{
-			$sql = 'SELECT DISTINCT a.*, c.category_name, c.category_id
+			// No DISTINCT: one category per article, and MSSQL cannot compare
+			// the text columns DISTINCT would have to
+			$sql = 'SELECT a.*, c.category_name, c.category_id
 				FROM ' . $this->articles_table . ' a, ' . $this->categories_table . ' c
 				WHERE article_id = ' . $art_id . '
 					AND (c.category_id = a.article_category_id)';

controller/search.php

@@ -320,7 +320,9 @@ public function main(): \Symfony\Component\HttpFoundation\Response
 		{
 			$sql_sort = $sort_by_sql[$sort_key] . (($sort_dir == 'a') ? ' ASC' : ' DESC');
 
-			$sql = 'SELECT DISTINCT a.*, u.user_id, u.username, u.user_colour
+			// No DISTINCT: one user per article, and MSSQL cannot compare the
+			// text columns DISTINCT would have to
+			$sql = 'SELECT a.*, u.user_id, u.username, u.user_colour
 					FROM ' . $this->articles_table . ' a
 					LEFT JOIN ' . USERS_TABLE . ' u ON (a.author_id = u.user_id AND a.author_type = 0)
 					WHERE ' . $this->db->sql_in_set('article_id', $id_ary) . '

docs/testing.md

@@ -1507,3 +1507,62 @@ also showed on the hierarchical index, and nothing showed once it was switched o
 
 Not covered: a board that never ran kinerity in a browser (the migration's off-by-default path is
 covered by PHPUnit), and other languages (the default text is English, as kinerity's was).
+
+## Enabling on MSSQL - 11/12/2026
+
+The extension could not be enabled on a fresh MSSQL board, on phpBB 3.3 or 4.0:
+
+- `version_1_0_0` inserts the seven `kb_options` rows with fixed ids. MSSQL refuses an explicit
+  value for an identity column unless `IDENTITY_INSERT` is on, so the insert now switches it on
+  and off around the rows on MSSQL, the way phpBB's own installer fills its ACL options.
+- `version_1_0_0` and `version_1_0_5` put numbers into `kb_config.config_value`, a text column
+  (`ntext` on MSSQL), which MSSQL refuses ("Operand type clash: int is incompatible with ntext").
+  The values are now strings.
+- `version_1_0_0` ran its extension-group query twice and never freed the first result, and
+  `version_2_0_0` never freed its `kb_config` result. MSSQL then refused the next transaction
+  ("New transaction is not allowed because there are other threads running in the session").
+
+Once enabled, two more things failed on MSSQL:
+
+- Adding the first category added 1 to `MAX(right_id)` of an empty table. phpBB's MSSQL driver
+  returns that NULL as an empty string, and `'' + 1` is a TypeError in PHP 8. Moving a category
+  to the root had the same sum. Both now cast to an integer.
+- Search, the article edit form and article comments used `SELECT DISTINCT` over rows with text
+  columns, which MSSQL cannot compare. Each join matches one row (one author, one category, one
+  poster), so `DISTINCT` is dropped.
+
+`kb_mssql_migration_test.php` (7 tests) checks the `IDENTITY_INSERT` statements on MSSQL and
+their absence elsewhere, the string config values, and that no result is left open.
+`kb_acp_first_category_test.php` checks the first root category with both NULL and an empty
+string from `MAX()`. Both files fail on the code before this change.
+
+`tests/browser/kb_page_sweep.js` is a read-only check for any seeded board: it logs in as the
+seed-forum administrator, opens the index, a category, an article, search, the queue, Manage
+Your Articles, recent changes and its RSS feed, the add and edit forms, and every Knowledge Base
+ACP module, and fails on a server error, a PHP error or phpBB's SQL error page. It loads only the
+HTML (styles, scripts and images are skipped), because PHP's built-in server serves them slowly.
+
+```bash
+KB_TEST_URL=http://localhost:8171 node /path/to/playwright-skill/run.js tests/browser/kb_page_sweep.js
+```
+
+Claude built a fresh seed-forum board with the full Knowledge Base fixtures for each of phpBB
+3.3.19 and 4.0.0-a3-dev on SQLite, MySQL 8.4, MariaDB, PostgreSQL 16 and MSSQL (SQL Server 2022),
+ten boards. On each, the sweep loaded 24 of 24 pages cleanly, and disabling, purging and enabling
+again through phpBB's CLI left no Knowledge Base migrations, tables, settings or ACP modules after
+the purge and all 40 migrations done after the enable. MSSQL boards run PHP 8.4 in seed-forum's
+driver image and are served with `bin/serve-board.py`; on a 3.3 board served that way, turn
+`enable_mod_rewrite` off first, since PHP's built-in server rewrites no clean URLs.
+
+The fresh-PostgreSQL fix (#12) gives `version_2_0_30`'s new option an explicit id, which MSSQL also
+only takes with `IDENTITY_INSERT` on, so `version_2_0_30::add_permission()` now switches it on and off
+around that insert on MSSQL as well; `kb_mssql_migration_test.php` covers it. The PostgreSQL boards,
+and an MSSQL 3.3 board run a second time, used this change merged with that fix and the wrapper,
+before #12 reached `main`.
+
+Building these boards needed three seed-forum fixes: a cache purge after enabling (seeds could not
+find the extension's services), GD in the MSSQL PHP image (the image fixtures), and several
+workers for `serve-board.py` (a browser's unused early connection held the single one).
+
+The PHPUnit suite passes on phpBB 3.3.x and master with the MySQL and PostgreSQL fixtures above:
+511 tests, none skipped.

migrations/version_1_0_0.php

@@ -346,7 +346,6 @@ public function set_default_config()
 			FROM ' . $this->table_prefix . 'extensions e, ' . $this->table_prefix . 'extension_groups g
 			WHERE e.group_id = g.group_id
 			AND g.allow_group = 1';
-		$this->db->sql_query($sql);
 		$result = $this->db->sql_query($sql);
 		while ($row = $this->db->sql_fetchrow($result))
 		{
@@ -388,18 +387,23 @@ public function set_default_config()
 		$result = $this->db->sql_query($sql);
 		$row = $this->db->sql_fetchrow($result);
 		$this->db->sql_freeresult($result);
+		// Every value is a string: config_value is a text column, and MSSQL
+		// refuses to put a number into one ("Operand type clash: int is
+		// incompatible with ntext")
+		$rows = [
+			'allow_attachments' => '0',
+			'max_filesize'      => (string) $max_filesize,
+			'extensions'        => $extensions,
+			'thumbnail'         => '0',
+			'max_attachments'   => '1',
+		];
 		if (empty($row))
 		{
-			$sql = 'INSERT INTO ' . $this->table_prefix . 'kb_config' . ' (config_name, config_value) VALUES
-				(\'allow_attachments\', 0),
-				(\'anounce\', 0),
-				(\'articles_per_page\', 10),
-				(\'forum_id\', 0),
-				(\'max_filesize\', ' . $max_filesize . '),
-				(\'extensions\', \'' . $extensions . '\'),
-				(\'thumbnail\', 0),
-				(\'max_attachments\', 1)
-				';
+			$rows += [
+				'anounce'           => '0',
+				'articles_per_page' => '10',
+				'forum_id'          => '0',
+			];
 		}
 		else
 		{
@@ -413,15 +417,14 @@ public function set_default_config()
 				$sql = 'ALTER TABLE ' . $this->table_prefix . 'kb_config CHANGE config_value config_value TEXT CHARACTER SET utf8 COLLATE utf8_bin';
 				$this->db->sql_query($sql);
 			}
-			$sql = 'INSERT INTO ' . $this->table_prefix . 'kb_config' . ' (config_name, config_value) VALUES
-				(\'allow_attachments\', 0),
-				(\'max_filesize\', ' . $max_filesize . '),
-				(\'extensions\', \'' . $extensions . '\'),
-				(\'thumbnail\', 0),
-				(\'max_attachments\', 1)
-				';
 		}
-		$this->db->sql_query($sql);
+
+		$sql_ary = [];
+		foreach ($rows as $config_name => $config_value)
+		{
+			$sql_ary[] = ['config_name' => $config_name, 'config_value' => $config_value];
+		}
+		$this->db->sql_multi_insert($this->table_prefix . 'kb_config', $sql_ary);
 	}
 
 	public function update_kb_options_table()
@@ -451,7 +454,19 @@ public function update_kb_options_table()
 					'is_local'       => 1,
 				];
 			}
+
+			// MSSQL only takes the fixed ids above with IDENTITY_INSERT on,
+			// the same way phpBB's own installer fills its ACL options
+			$identity_insert = strpos($this->db->get_sql_layer(), 'mssql') === 0;
+			if ($identity_insert)
+			{
+				$this->db->sql_query('SET IDENTITY_INSERT ' . $this->table_prefix . 'kb_options ON');
+			}
 			$this->db->sql_multi_insert($this->table_prefix . 'kb_options', $sql_ary);
+			if ($identity_insert)
+			{
+				$this->db->sql_query('SET IDENTITY_INSERT ' . $this->table_prefix . 'kb_options OFF');
+			}
 		}
 	}
 

migrations/version_1_0_5.php

@@ -54,8 +54,12 @@ public function update_data()
 
 	public function add_config()
 	{
-		$sql = 'INSERT INTO ' . $this->table_prefix . 'kb_config' . ' (config_name, config_value) VALUES
-			(\'sort_type\', 0)';
+		// A string: config_value is a text column, which MSSQL will not
+		// compare with or fill from a number
+		$sql = 'INSERT INTO ' . $this->table_prefix . 'kb_config ' . $this->db->sql_build_array('INSERT', [
+			'config_name'  => 'sort_type',
+			'config_value' => '0',
+		]);
 		$this->db->sql_query($sql);
 	}
 }

migrations/version_2_0_0.php

@@ -41,6 +41,8 @@ public function update_schema()
 		{
 			$this->config[$row['config_name']] = $row['config_value'];
 		}
+		// MSSQL refuses to start a transaction while a result is still open
+		$this->db->sql_freeresult($result);
 
 		// Drop table
 		return [

migrations/version_2_0_30.php

@@ -39,9 +39,19 @@ public function add_permission(): void
 			$next_id = (int) $this->db->sql_fetchfield('max_id') + 1;
 			$this->db->sql_freeresult($result);
 
+			// MSSQL only takes an explicit id with IDENTITY_INSERT on
+			$identity_insert = strpos($this->db->get_sql_layer(), 'mssql') === 0;
+			if ($identity_insert)
+			{
+				$this->db->sql_query('SET IDENTITY_INSERT ' . $this->table_prefix . 'kb_options ON');
+			}
 			$this->db->sql_query('INSERT INTO ' . $this->table_prefix . 'kb_options ' . $this->db->sql_build_array('INSERT', [
 				'auth_option_id' => $next_id, 'auth_option' => 'kb_m_change_author', 'is_global' => 0, 'is_local' => 1,
 			]));
+			if ($identity_insert)
+			{
+				$this->db->sql_query('SET IDENTITY_INSERT ' . $this->table_prefix . 'kb_options OFF');
+			}
 		}
 	}
 

tests/browser/kb_page_sweep.js

@@ -0,0 +1,121 @@
+// Load every main Knowledge Base page and every Knowledge Base ACP module as
+// the seeded administrator, and fail on a server error, a PHP error or
+// phpBB's SQL error page. Read-only: it opens pages and submits nothing but
+// the login forms, so it suits any seed-forum board on any database.
+//
+// KB_TEST_URL is the board's base URL, without a trailing slash. Routes go
+// through app.php, so the board needs no clean-URL rewriting.
+// KB_ARTIFACT_DIR optionally saves a screenshot of each page that fails.
+const {chromium} = require('playwright');
+const fs = require('node:fs');
+
+const base = process.env.KB_TEST_URL;
+if (!/^http:\/\/(localhost|127\.0\.0\.1):\d+$/.test(base || '')) throw new Error('Set KB_TEST_URL to a disposable local board, for example http://localhost:8171');
+const out = process.env.KB_ARTIFACT_DIR;
+const password = 'KbTest1234!';
+
+// Text that only shows up when a page broke
+const ERROR_MARKERS = ['SQL ERROR', 'Fatal error', 'Parse error', 'Uncaught', 'General Error', '[phpBB Debug]', 'Warning</b>:', 'Notice</b>:', 'Deprecated</b>:'];
+
+// phpBB refuses a form submitted within two seconds of it being made
+async function waitForFormAge(page) {
+	await page.waitForFunction(() => {
+		const field = document.querySelector('[name="creation_time"]');
+		return field && Date.now() / 1000 > Number(field.value) + 2;
+	});
+}
+
+(async () => {
+	const browser = await chromium.launch({headless: true});
+	const page = await browser.newPage({viewport: {width: 1280, height: 900}});
+	// PHP's built-in server (MSSQL boards) serves styles and scripts slowly, so
+	// pages are checked once their HTML is in, without waiting for every asset
+	page.setDefaultTimeout(120000);
+	const ready = {waitUntil: 'domcontentloaded'};
+	// Only the HTML is checked, and scripts would hold up domcontentloaded
+	await page.route(/\.(css|js|png|gif|jpe?g|svg|ico|woff2?|ttf)(\?|$)/, route => route.abort());
+	const results = [];
+
+	async function check(label, url) {
+		const response = await page.goto(url, ready);
+		const body = await page.content();
+		const problems = [];
+		if (!response || response.status() >= 500) problems.push(`HTTP ${response ? response.status() : 'no response'}`);
+		for (const marker of ERROR_MARKERS) {
+			if (body.includes(marker)) problems.push(marker);
+		}
+		if (problems.length) {
+			// phpBB's error page message, for the SQL error and query
+			const text = await page.locator('body').innerText();
+			const at = Math.max(0, text.search(/SQL ERROR|Fatal error|General Error|Warning|Notice/));
+			problems.push(JSON.stringify(text.slice(at, at + 600)));
+		}
+		if (problems.length && out) {
+			fs.mkdirSync(out, {recursive: true});
+			await page.screenshot({path: `${out}/${label.replace(/[^a-z0-9]+/gi, '-')}.png`, fullPage: true});
+		}
+		results.push({label, status: response ? response.status() : 0, problems});
+		return body;
+	}
+
+	try {
+		// Board login
+		await page.goto(`${base}/ucp.php?mode=login`, ready);
+		await page.locator('#username').fill('admin');
+		await page.locator('#password').fill(password);
+		await waitForFormAge(page);
+		await page.locator('[name="login"][type="submit"]').click();
+		await page.waitForURL(url => !url.search.includes('mode=login'), ready);
+
+		// Front end: the index, then the first category and article it links to
+		await check('index', `${base}/app.php/knowledgebase`);
+		const category = await firstLink(page, 'knowledgebase/category?id=');
+		const article = await firstLink(page, 'knowledgebase/article?k=');
+		if (!category || !article) throw new Error('The index links to no category or article; seed the board first');
+		await check('category', category);
+		await check('article', article);
+		await check('search', `${base}/app.php/knowledgebase/search?keywords=guide&sf=all&cid=0`);
+		await check('queue', `${base}/app.php/knowledgebase/queue`);
+		await check('my articles', `${base}/app.php/knowledgebase/my_articles`);
+		await check('recent changes', `${base}/app.php/knowledgebase/recent_changes`);
+		await check('recent changes rss', `${base}/app.php/knowledgebase/recent_changes.rss`);
+		await check('posting form', `${base}/app.php/knowledgebase/posting?mode=add`);
+		await check('edit form', `${base}/app.php/knowledgebase/posting?mode=edit&id=${new URL(article).searchParams.get('k')}`);
+
+		// ACP: it needs the session id in the address, and the password again
+		const settings = '/adm/index.php?i=-phpbbmodders-knowledgebase-acp-config_module&mode=settings';
+		await page.goto(`${base}${settings}&sid=${await sessionCookie(page)}`, ready);
+		if (await page.locator('input[type="password"]').count()) {
+			await page.locator('input[type="password"]').fill(password);
+			await waitForFormAge(page);
+			// phpBB 4.0 keeps the ACP session in the cookie, so the address may not change
+			await Promise.all([page.waitForNavigation(ready), page.locator('[name="login"][type="submit"]').click()]);
+		}
+		await check('acp settings', `${base}${settings}&sid=${await sessionCookie(page)}`);
+		const modules = await page.locator('#menu a[href*="i=-phpbbmodders-knowledgebase-acp-"]').evaluateAll(links => links.map(link => [link.textContent.trim(), link.href]));
+		if (!modules.length) throw new Error('No Knowledge Base modules in the ACP menu');
+		for (const [label, href] of modules) await check(`acp ${label}`, href);
+	} finally {
+		await browser.close();
+	}
+
+	const failed = results.filter(result => result.problems.length);
+	for (const result of results) console.log(`${result.problems.length ? 'FAIL' : 'ok  '} ${result.status} ${result.label}${result.problems.length ? ': ' + result.problems.join(', ') : ''}`);
+	console.log(`${results.length - failed.length} of ${results.length} pages loaded cleanly`);
+	process.exitCode = failed.length ? 1 : 0;
+})();
+
+// The first link on the page whose address contains the text, or null
+async function firstLink(page, text) {
+	return page.locator('a').evaluateAll((links, part) => {
+		// Skip same-page anchors, which load nothing
+		const link = links.find(a => a.href.includes(part) && !a.href.includes('#'));
+		return link ? link.href : null;
+	}, text);
+}
+
+// The session id from phpBB's cookie, which every ACP address must carry
+async function sessionCookie(page) {
+	const cookie = (await page.context().cookies()).find(item => item.name.endsWith('_sid'));
+	return cookie ? cookie.value : '';
+}