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batch3 T2 review fixes: movePane sentinel + count race + PATCH atomicity

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- Move sentinel from -1 to -100 (outside the negate range) so moves from
  position 0 no longer collide with negated row at -1
- Pull count check + position validation inside sql.begin in POST so two
  concurrent inserts can't both pass the max-5 guard
- Wrap movePane + state UPDATE in a single transaction in PATCH so partial
  failures roll back consistently

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
indifferentketchup
2026-05-15 14:58:49 +00:00
parent 2bc626a40a
commit 493df5f25d
1 changed files with 62 additions and 52 deletions
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114
apps/server/src/routes/panes.ts
View File

@@ -1,4 +1,5 @@
import type { FastifyInstance } from 'fastify';
import type { TransactionSql } from 'postgres';
import type { Sql } from '../db.js';
import type { Pane, PaneCreateRequest, PaneUpdateRequest } from '../types/api.js';
@@ -6,29 +7,28 @@ const VALID_KINDS = new Set(['chat', 'file_browser']);
const MAX_PANES = 5;
async function movePane(
sql: Sql,
tx: TransactionSql,
paneId: string,
sid: string,
oldPos: number,
newPos: number
): Promise<void> {
if (oldPos === newPos) return;
await sql.begin(async (tx) => {
// Move target pane to temporary negative slot to avoid collision
await tx`UPDATE session_panes SET position = -1 WHERE id = ${paneId}`;
if (newPos > oldPos) {
await tx`UPDATE session_panes SET position = -position
WHERE session_id = ${sid} AND position > ${oldPos} AND position <= ${newPos}`;
await tx`UPDATE session_panes SET position = -position - 1
WHERE session_id = ${sid} AND position < 0 AND id != ${paneId}`;
} else {
await tx`UPDATE session_panes SET position = -position - 2
WHERE session_id = ${sid} AND position >= ${newPos} AND position < ${oldPos}`;
await tx`UPDATE session_panes SET position = -position - 1
WHERE session_id = ${sid} AND position < -1`;
}
await tx`UPDATE session_panes SET position = ${newPos} WHERE id = ${paneId}`;
});
// Move target pane to a sentinel well outside the negate range [-MAX_PANES, -1]
// so it never collides with negated rows during the shift steps.
await tx`UPDATE session_panes SET position = -100 WHERE id = ${paneId}`;
if (newPos > oldPos) {
await tx`UPDATE session_panes SET position = -position
WHERE session_id = ${sid} AND position > ${oldPos} AND position <= ${newPos}`;
await tx`UPDATE session_panes SET position = -position - 1
WHERE session_id = ${sid} AND position < 0 AND id != ${paneId}`;
} else {
await tx`UPDATE session_panes SET position = -position - 2
WHERE session_id = ${sid} AND position >= ${newPos} AND position < ${oldPos}`;
await tx`UPDATE session_panes SET position = -position - 1
WHERE session_id = ${sid} AND position < 0 AND id != ${paneId}`;
}
await tx`UPDATE session_panes SET position = ${newPos} WHERE id = ${paneId}`;
}
export function registerPaneRoutes(app: FastifyInstance, sql: Sql): void {
@@ -70,32 +70,26 @@ export function registerPaneRoutes(app: FastifyInstance, sql: Sql): void {
}
const sid = req.params.id;
const countRows = await sql<{ n: number }[]>`
SELECT COUNT(*)::int AS n FROM session_panes WHERE session_id = ${sid}
`;
const count = countRows[0]?.n ?? 0;
if (count >= MAX_PANES) {
reply.code(400);
return { error: `session already has ${MAX_PANES} panes (maximum)` };
}
// Determine insert position
let insertPos: number;
if (position === undefined || position === null) {
insertPos = count;
} else {
if (position < 0 || position > count) {
reply.code(400);
return { error: `position must be between 0 and ${count} (existing count)` };
}
insertPos = position;
}
const state = {};
let insertError: string | null = null;
const inserted = await sql.begin(async (tx) => {
const countResult = await tx<{ n: number }[]>`
SELECT COUNT(*)::int AS n FROM session_panes WHERE session_id = ${sid}
`;
const n = countResult[0]!.n;
if (n >= MAX_PANES) {
throw new Error('MAX_PANES_EXCEEDED');
}
let insertPos: number;
if (position === undefined || position === null) {
insertPos = n;
} else {
if (position < 0 || position > n) {
throw new Error('OUT_OF_BOUNDS');
}
insertPos = position;
}
await tx`UPDATE session_panes SET position = -position - 1
WHERE session_id = ${sid} AND position >= ${insertPos}`;
const [row] = await tx<Pane[]>`
@@ -106,8 +100,24 @@ export function registerPaneRoutes(app: FastifyInstance, sql: Sql): void {
await tx`UPDATE session_panes SET position = -position
WHERE session_id = ${sid} AND position < 0`;
return row;
}).catch((err: Error) => {
insertError = err.message;
return null;
});
if (insertError === 'MAX_PANES_EXCEEDED') {
reply.code(400);
return { error: `session already has ${MAX_PANES} panes (maximum)` };
}
if (insertError === 'OUT_OF_BOUNDS') {
reply.code(400);
return { error: `position out of bounds` };
}
if (insertError) {
reply.code(500);
return { error: 'internal error' };
}
reply.code(201);
return inserted as Pane;
}
@@ -149,18 +159,18 @@ export function registerPaneRoutes(app: FastifyInstance, sql: Sql): void {
}
}
// Apply position change if needed
if (position !== undefined && position !== oldPos) {
await movePane(sql, req.params.id, sid, oldPos, position);
}
// Apply state change if provided
if (state !== undefined) {
await sql`
UPDATE session_panes SET state = ${JSON.stringify(state)}::jsonb
WHERE id = ${req.params.id}
`;
}
// Apply position and/or state changes atomically
await sql.begin(async (tx) => {
if (position !== undefined && position !== oldPos) {
await movePane(tx, req.params.id, sid, oldPos, position);
}
if (state !== undefined) {
await tx`
UPDATE session_panes SET state = ${JSON.stringify(state)}::jsonb
WHERE id = ${req.params.id}
`;
}
});
const [updated] = await sql<Pane[]>`
SELECT id, session_id, position, kind, state, created_at