BlockAnchorReplacer is too loose with single-candidate weak anchors #14046
Description
Description
Attempts to apply a change run BlockAnchorReplacer, which finds candidates for replacement. If only one candidate is found, the algorithm's threshold for acceptance is 0.0. When one of the anchors is very common (e.g., }), effectively this equates to searching for a single line of matching code, and can replace on the basis of completely hallucinated code. The resulting replacement might even yield invalid code (e.g., replacing the first } when the block closed at a later line).
One possible fix could be to count to count the occurrence of the anchors (in addition to the candidates), and use a higher threshold if one of the anchors is not very unique. Another option (which wouldn't necessarily fix my repro script) would be to compare the block sizes of the search and the match.
Plugins
No response
OpenCode version
1.2.6
Steps to reproduce
import { replace } from "./packages/opencode/src/tool/edit"
const content = `class DatabaseConnection {
private pool: ConnectionPool
constructor(config: DbConfig) {
this.pool = new ConnectionPool(config)
}
async query(sql: string, params: unknown[]) {
const conn = await this.pool.acquire()
try {
const result = await conn.execute(sql, params)
return result.rows
} finally {
this.pool.release(conn)
}
}
async transaction<T>(fn: (tx: Transaction) => Promise<T>): Promise<T> {
const conn = await this.pool.acquire()
const tx = await conn.beginTransaction()
try {
const result = await fn(tx)
await tx.commit()
return result
} catch (e) {
await tx.rollback()
throw e
} finally {
this.pool.release(conn)
}
}
}`
const oldString = ` async query(sql: string, params: unknown[]) {
validateSqlInjection(sql)
const sanitized = escapeSqlParams(params)
const cache = QueryCache.get(sql)
if (cache) return cache
const response = await fetch("/api/query", { body: JSON.stringify({ sql, params: sanitized }) })
const data = await response.json()
QueryCache.set(sql, data)
return data
}`
const newString = ` async query(sql: string, params: unknown[]) {
validateSqlInjection(sql)
const sanitized = escapeSqlParams(params)
const cache = QueryCache.get(sql)
if (cache) return cache
logger.debug("Executing query", { sql })
const response = await fetch("/api/query", { body: JSON.stringify({ sql, params: sanitized }) })
const data = await response.json()
QueryCache.set(sql, data)
return data
}`
replace(content, oldString, newString) // should throw but does notScreenshot and/or share link
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Operating System
No response
Terminal
No response