From 19e29c34654e2105ba78587a6e9feaf8c799b5d7 Mon Sep 17 00:00:00 2001
From: Francis Dinh <normandy@biribiri.dev>
Date: Thu, 8 Sep 2022 16:17:35 -0400
Subject: [PATCH 1/2] backend: move mentionedUsers query to mention handler

The mentionedUsers query was being run on every post, regardless of
whether a mention was in it or not.

This resulted in an SQL query ending in `WHERE userId IN ()` which is
not allowed in PostgreSQL.

Reference: https://akkoma.dev/FoundKeyGang/FoundKey/issues/132
Changelog: Fixed
---
 packages/backend/src/mfm/to-html.ts | 37 ++++++++++++++---------------
 1 file changed, 18 insertions(+), 19 deletions(-)

diff --git a/packages/backend/src/mfm/to-html.ts b/packages/backend/src/mfm/to-html.ts
index 117f8b278..9b72b98c6 100644
--- a/packages/backend/src/mfm/to-html.ts
+++ b/packages/backend/src/mfm/to-html.ts
@@ -14,23 +14,8 @@ export async function toHtml(mfmText: string, mentions?: string[]): Promise<stri
 		return null;
 	}
 
-	const mentionedUsers = await UserProfiles.createQueryBuilder('user_profile')
-		.leftJoin('user_profile.user', 'user')
-		.select('user.username')
-		.addSelect('user.host')
-		// links should preferably use user friendly urls, only fall back to AP ids
-		.addSelect('COALESCE(user_profile.url, user.uri)', 'url')
-		.where('userId IN (:...ids)', { ids: mentions ?? extractMentions(nodes) })
-		.getMany();
-
 	const doc = new JSDOM('').window.document;
 
-	function appendChildren(children: mfm.MfmNode[], targetElement: any): void {
-		if (children) {
-			for (const child of children.map(x => (handlers as any)[x.type](x))) targetElement.appendChild(child);
-		}
-	}
-
 	const handlers: { [K in mfm.MfmNode['type']]: (node: mfm.NodeType<K>) => any } = {
 		bold(node) {
 			const el = doc.createElement('b');
@@ -117,8 +102,17 @@ export async function toHtml(mfmText: string, mentions?: string[]): Promise<stri
 			return a;
 		},
 
-		mention(node) {
+		async mention(node): Promise<HTMLElement | Text> {
 			const { username, host, acct } = node.props;
+			const ids = mentions ?? extractMentions(nodes);
+			const mentionedUsers = await UserProfiles.createQueryBuilder('user_profile')
+				.leftJoin('user_profile.user', 'user')
+				.select('user.username')
+				.addSelect('user.host')
+				// links should preferably use user friendly urls, only fall back to AP ids
+				.addSelect('COALESCE(user_profile.url, user.uri)', 'url')
+				.where('userId IN (:...ids)', { ids })
+				.getMany();
 			const userInfo = mentionedUsers.find(user => user.user?.username === username && user.userHost === host);
 			if (userInfo != null) {
 				// Mastodon microformat: span.h-card > a.u-url.mention
@@ -131,10 +125,9 @@ export async function toHtml(mfmText: string, mentions?: string[]): Promise<stri
 				card.className = 'h-card';
 				card.appendChild(a);
 				return card;
-			} else {
-				// this user does not actually exist
-				return doc.createTextNode(acct);
 			}
+			// this user does not actually exist
+			return doc.createTextNode(acct);
 		},
 
 		quote(node) {
@@ -169,6 +162,12 @@ export async function toHtml(mfmText: string, mentions?: string[]): Promise<stri
 		},
 	};
 
+	function appendChildren(children: mfm.MfmNode[], targetElement: any): void {
+		if (children.length > 0) {
+			for (const child of children.map(x => (handlers as any)[x.type](x))) targetElement.appendChild(child);
+		}
+	}
+
 	appendChildren(nodes, doc.body);
 
 	return `<p>${doc.body.innerHTML}</p>`;

From 199622b41548110a2dee84983b93fe68388b20b8 Mon Sep 17 00:00:00 2001
From: Francis Dinh <normandy@biribiri.dev>
Date: Thu, 8 Sep 2022 17:45:03 -0400
Subject: [PATCH 2/2] add check if ids.length > 0 before executing query

---
 packages/backend/src/mfm/to-html.ts | 40 +++++++++++++++--------------
 1 file changed, 21 insertions(+), 19 deletions(-)

diff --git a/packages/backend/src/mfm/to-html.ts b/packages/backend/src/mfm/to-html.ts
index 9b72b98c6..c32363574 100644
--- a/packages/backend/src/mfm/to-html.ts
+++ b/packages/backend/src/mfm/to-html.ts
@@ -105,26 +105,28 @@ export async function toHtml(mfmText: string, mentions?: string[]): Promise<stri
 		async mention(node): Promise<HTMLElement | Text> {
 			const { username, host, acct } = node.props;
 			const ids = mentions ?? extractMentions(nodes);
-			const mentionedUsers = await UserProfiles.createQueryBuilder('user_profile')
-				.leftJoin('user_profile.user', 'user')
-				.select('user.username')
-				.addSelect('user.host')
-				// links should preferably use user friendly urls, only fall back to AP ids
-				.addSelect('COALESCE(user_profile.url, user.uri)', 'url')
-				.where('userId IN (:...ids)', { ids })
-				.getMany();
-			const userInfo = mentionedUsers.find(user => user.user?.username === username && user.userHost === host);
-			if (userInfo != null) {
-				// Mastodon microformat: span.h-card > a.u-url.mention
-				const a = doc.createElement('a');
-				a.href = userInfo.url ?? `${config.url}/${acct}`;
-				a.className = 'u-url mention';
-				a.textContent = acct;
+			if (ids.length > 0) {
+				const mentionedUsers = await UserProfiles.createQueryBuilder('user_profile')
+					.leftJoin('user_profile.user', 'user')
+					.select('user.username')
+					.addSelect('user.host')
+					// links should preferably use user friendly urls, only fall back to AP ids
+					.addSelect('COALESCE(user_profile.url, user.uri)', 'url')
+					.where('"userId" IN (:...ids)', { ids })
+					.getMany();
+				const userInfo = mentionedUsers.find(user => user.user?.username === username && user.userHost === host);
+				if (userInfo != null) {
+					// Mastodon microformat: span.h-card > a.u-url.mention
+					const a = doc.createElement('a');
+					a.href = userInfo.url ?? `${config.url}/${acct}`;
+					a.className = 'u-url mention';
+					a.textContent = acct;
 
-				const card = doc.createElement('span');
-				card.className = 'h-card';
-				card.appendChild(a);
-				return card;
+					const card = doc.createElement('span');
+					card.className = 'h-card';
+					card.appendChild(a);
+					return card;
+				}
 			}
 			// this user does not actually exist
 			return doc.createTextNode(acct);