Fix panics on unknown Postgres type oid when decoding (#1855)

Postgres arrays and records do not fully support custom types. When encountering an unknown OID, they currently default to using `PgTypeInfo::with_oid`. This is invalid as it breaks the invariant that decoding only uses resolved types, leading to panics.

This commit returns an error instead of panicking. This is merely a mitigation: a proper fix would actually add full support for custom Postgres types. Full support involves more work, so it may still be useful to fix this immediate issue.

Related issues:
- #1672
- #1797

sqlx-core/src/postgres/types/array.rs

@@ -134,7 +134,12 @@ where
                 let element_type_oid = Oid(buf.get_u32());
                 let element_type_info: PgTypeInfo = PgTypeInfo::try_from_oid(element_type_oid)
                     .or_else(|| value.type_info.try_array_element().map(Cow::into_owned))
-                    .unwrap_or_else(|| PgTypeInfo(PgType::DeclareWithOid(element_type_oid)));
+                    .ok_or_else(|| {
+                        BoxDynError::from(format!(
+                            "failed to resolve array element type for oid {}",
+                            element_type_oid.0
+                        ))
+                    })?;
 
                 // length of the array axis
                 let len = buf.get_i32();

sqlx-core/src/postgres/types/record.rs

@@ -125,16 +125,17 @@ impl<'r> PgRecordDecoder<'r> {
                     }
                 };
 
-                self.ind += 1;
-
                 if let Some(ty) = &element_type_opt {
                     if !ty.is_null() && !T::compatible(ty) {
                         return Err(mismatched_types::<Postgres, T>(ty));
                     }
                 }
 
                 let element_type =
-                    element_type_opt.unwrap_or_else(|| PgTypeInfo::with_oid(element_type_oid));
+                    element_type_opt
+                        .ok_or_else(|| BoxDynError::from(format!("custom types in records are not fully supported yet: failed to retrieve type info for field {} with type oid {}", self.ind, element_type_oid.0)))?;
+
+                self.ind += 1;
 
                 T::decode(PgValueRef::get(&mut self.buf, self.fmt, element_type))
             }

sqlx-core/src/query_builder.rs

@@ -224,7 +224,7 @@ where
     ///     // e.g. collect it to a `Vec` first.
     ///     b.push_bind(user.id)
     ///         .push_bind(user.username)
-    ///         .push_bind(user.email)    
+    ///         .push_bind(user.email)
     ///         .push_bind(user.password);
     /// });
     ///
@@ -310,6 +310,7 @@ where
 /// A wrapper around `QueryBuilder` for creating comma(or other token)-separated lists.
 ///
 /// See [`QueryBuilder::separated()`] for details.
+#[allow(explicit_outlives_requirements)]
 pub struct Separated<'qb, 'args: 'qb, DB, Sep>
 where
     DB: Database,

tests/postgres/postgres.rs

@@ -1200,6 +1200,160 @@ VALUES
     Ok(())
 }
 
+#[sqlx_macros::test]
+async fn it_resolves_custom_types_in_anonymous_records() -> anyhow::Result<()> {
+    use sqlx_core::error::Error;
+    // This request involves nested records and array types.
+
+    // Only supported in Postgres 11+
+    let mut conn = new::<Postgres>().await?;
+    if matches!(conn.server_version_num(), Some(version) if version < 110000) {
+        return Ok(());
+    }
+
+    // language=PostgreSQL
+    conn.execute(
+        r#"
+DROP TABLE IF EXISTS repo_users;
+DROP TABLE IF EXISTS repositories;
+DROP TABLE IF EXISTS repo_memberships;
+DROP TYPE IF EXISTS repo_member;
+
+CREATE TABLE repo_users (
+  user_id INT4 NOT NULL,
+  username TEXT NOT NULL,
+  PRIMARY KEY (user_id)
+);
+CREATE TABLE repositories (
+  repo_id INT4 NOT NULL,
+  repo_name TEXT NOT NULL,
+  PRIMARY KEY (repo_id)
+);
+CREATE TABLE repo_memberships (
+  repo_id INT4 NOT NULL,
+  user_id INT4 NOT NULL,
+  permission TEXT NOT NULL,
+  PRIMARY KEY (repo_id, user_id)
+);
+CREATE TYPE repo_member AS (
+  user_id INT4,
+  permission TEXT
+);
+INSERT INTO repo_users(user_id, username)
+VALUES
+  (101, 'alice'),
+  (102, 'bob'),
+  (103, 'charlie');
+INSERT INTO repositories(repo_id, repo_name)
+VALUES
+  (201, 'rust'),
+  (202, 'sqlx'),
+  (203, 'hello-world');
+INSERT INTO repo_memberships(repo_id, user_id, permission)
+VALUES
+  (201, 101, 'admin'),
+  (201, 102, 'write'),
+  (201, 103, 'read'),
+  (202, 102, 'admin');
+"#,
+    )
+    .await?;
+
+    #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+    struct RepoMember {
+        user_id: i32,
+        permission: String,
+    }
+
+    impl sqlx::Type<Postgres> for RepoMember {
+        fn type_info() -> sqlx::postgres::PgTypeInfo {
+            sqlx::postgres::PgTypeInfo::with_name("repo_member")
+        }
+    }
+
+    impl<'r> sqlx::Decode<'r, Postgres> for RepoMember {
+        fn decode(
+            value: sqlx::postgres::PgValueRef<'r>,
+        ) -> Result<Self, Box<dyn std::error::Error + 'static + Send + Sync>> {
+            let mut decoder = sqlx::postgres::types::PgRecordDecoder::new(value)?;
+            let user_id = decoder.try_decode::<i32>()?;
+            let permission = decoder.try_decode::<String>()?;
+            Ok(Self {
+                user_id,
+                permission,
+            })
+        }
+    }
+
+    #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+    struct RepoMemberArray(Vec<RepoMember>);
+
+    impl sqlx::Type<Postgres> for RepoMemberArray {
+        fn type_info() -> sqlx::postgres::PgTypeInfo {
+            // Array type name is the name of the element type prefixed with `_`
+            sqlx::postgres::PgTypeInfo::with_name("_repo_member")
+        }
+    }
+
+    impl<'r> sqlx::Decode<'r, Postgres> for RepoMemberArray {
+        fn decode(
+            value: sqlx::postgres::PgValueRef<'r>,
+        ) -> Result<Self, Box<dyn std::error::Error + 'static + Send + Sync>> {
+            Ok(Self(Vec::<RepoMember>::decode(value)?))
+        }
+    }
+
+    let mut conn = new::<Postgres>().await?;
+
+    #[derive(Debug, sqlx::FromRow)]
+    struct Row {
+        count: i64,
+        items: Vec<(i32, String, RepoMemberArray)>,
+    }
+    // language=PostgreSQL
+    let row: Result<Row, Error> = sqlx::query_as::<_, Row>(
+        r"
+        WITH
+          members_by_repo AS (
+            SELECT repo_id,
+              ARRAY_AGG(ROW (user_id, permission)::repo_member) AS members
+            FROM repo_memberships
+            GROUP BY repo_id
+          ),
+          repos AS (
+            SELECT repo_id, repo_name, COALESCE(members, '{}') AS members
+            FROM repositories
+              LEFT OUTER JOIN members_by_repo USING (repo_id)
+            ORDER BY repo_id
+          ),
+          repo_array AS (
+            SELECT COALESCE(ARRAY_AGG(repos.*), '{}') AS items
+            FROM repos
+          ),
+          repo_count AS (
+            SELECT COUNT(*) AS count
+            FROM repos
+          )
+        SELECT count, items
+        FROM repo_count, repo_array
+        ;
+    ",
+    )
+    .fetch_one(&mut conn)
+    .await;
+
+    // This test currently tests mitigations for `#1672` (use regular errors
+    // instead of panics). Once we fully support custom types, it should be
+    // updated accordingly.
+    match row {
+        Ok(_) => panic!("full support for custom types is not implemented yet"),
+        Err(e) => assert!(e
+            .to_string()
+            .contains("custom types in records are not fully supported yet")),
+    }
+    Ok(())
+}
+
 #[sqlx_macros::test]
 async fn test_pg_server_num() -> anyhow::Result<()> {
     let conn = new::<Postgres>().await?;