Regression: the trait PgHasArrayType is not implemented for serde_json::Value

[abreis]

After an update to sqlx 0.5.10 I'm now seeing this error:

error[E0277]: the trait bound `serde_json::Value: PgHasArrayType` is not satisfied
   --> pkg/database/src/app.rs:141:15
    |
141 |         .bind(col_fields)
    |          ---- ^^^^^^^^^^ the trait `PgHasArrayType` is not implemented for `serde_json::Value`
    |          |
    |          required by a bound introduced by this call
    |
    = note: required because of the requirements on the impl of `PgHasArrayType` for `std::option::Option<serde_json::Value>`
    = note: required because of the requirements on the impl of `Type<Postgres>` for `Vec<std::option::Option<serde_json::Value>>`

The underlying code is trying to bind() a Vec<Option<JsonValue>> for an UNNEST statement.

Cargo.toml is:

sqlx = { version = "=0.5.10", default-features = false, features = ["postgres", "chrono", "decimal", "json", "uuid", "runtime-tokio-native-tls", "macros", "migrate", "offline"] }

Reverting to sqlx 0.5.7 makes the error go away.

If there's anything I can do to help track this down please let me know. Thanks!

[abonander]

Seems to be a bad interaction between various changes in #1385

I think adding a PgHasArrayType impl for JsonValue will fix it. You could just copy the one for Json<T>.

[abreis]

I gave it a try but now there's a couple conflicting impls (between [T] where T: PgHasArrayType and [JsonValue]). Perhaps one of those is no longer needed after #1385.

error[E0119]: conflicting implementations of trait `types::Type<postgres::database::Postgres>` for type `[serde_json::Value]`
  --> /Users/abreis/.cargo/git/checkouts/sqlx-28e322958903bd10/97b68a4/sqlx-core/src/postgres/types/array.rs:31:1
   |
31 | / impl<T> Type<Postgres> for [T]
32 | | where
33 | |     T: PgHasArrayType,
34 | | {
...  |
41 | |     }
42 | | }
   | |_^ conflicting implementation for `[serde_json::Value]`
   |
  ::: /Users/abreis/.cargo/git/checkouts/sqlx-28e322958903bd10/97b68a4/sqlx-core/src/types/json.rs:73:1
   |
73 | / impl<DB> Type<DB> for [JsonValue]
74 | | where
75 | |     [Json<JsonValue>]: Type<DB>,
76 | |     DB: Database,
...  |
84 | |     }
85 | | }
   | |_- first implementation here

[abonander]

Another possibility might be to change this bound: https://github.com/launchbadge/sqlx/blob/master/sqlx-core/src/postgres/types/array.rs#L20

to [T]: Type<Postgres>, which should hopefully not break anything else?

[jplatte]

but now there's a couple conflicting impls

Yeah it looks like impl<DB> Type<DB> for Vec<JsonValue> and impl<DB> Type<DB> for [JsonValue] are a thing. These might be the only DB-agnostic array impls? But they have bounds for the corresponding container with an item type of Json<JsonValue> implementing Type<DB>, so I think in the end they're only applicable to postgres anyways? If they are, they can safely be removed in favor of one PgHasArrayType impl for JsonValue.

[abreis]

That worked, let me open a PR to see if it nothing else broke.