diesel::insert compilation error

[attdona]

Setup

Versions

• Rust: rustc 1.22.0-nightly (417c73891 2017-10-05)
• Diesel: 0.16.0
• Database: postgres
• Operating System ubuntu 17.10

Problem Description

This code snippet:

fn add_user(db: DB, message: Json<User>) -> JsonValue {
    use schema::users::dsl::*;


    //diesel::insert(&NewUser {name: &message.name})
    diesel::insert(&name.eq(message.name))
        .into(users)
        .execute(db.conn())
        .expect("Error saving new user");

    json!({ "status": "ok" })
}

Throws the compile error:

error[E0061]: this function takes 0 parameters but 1 parameter was supplied
   --> src/main.rs:136:15
    |
136 |         .into(users)
    |               ^^^^^ expected 0 parameters

error: aborting due to previous error

Using a struct for value (the commented line) rustc compiles.

What is going wrong? I don't understand the error message.

Greetings
Attilio

[weiznich]

diesel::insert currently only supports inserting structs. The error message is indicting that in a really bad way. Rustc assumes one wants to use Into::into instead of IncompleteInsertStatement::into.

On diesels master-branch the story around insert changed drastically. The new insert_into method allows setting values directly and also improves the error message.

[attdona]

Ok, it make sense for me to try the latest diesel.
I've pointed diesel to master-branch, but now this code stop compiling:

#[macro_use]
extern crate diesel_codegen;
#[macro_use]
extern crate diesel;
extern crate dotenv;
extern crate r2d2;
extern crate r2d2_diesel;

pub mod schema;
pub mod models;

use diesel::pg::PgConnection;
use r2d2::{ Pool, Config };
use r2d2_diesel::ConnectionManager;
use dotenv::dotenv;
use std::env;

pub fn create_db_pool() -> Pool<ConnectionManager<PgConnection>> {
    dotenv().ok();

    let database_url = env::var("DATABASE_URL")
        .expect("DATABASE_URL must be set");
    let config = Config::default();
    let manager = ConnectionManager::<PgConnection>::new(database_url);
    Pool::new(config, manager).expect("Failed to create pool.")
}

rustc output:

error[E0277]: the trait bound `diesel::PgConnection: diesel::connection::Connection` is not satisfied
  --> src/lib.rs:18:1
   |
18 | / pub fn create_db_pool() -> Pool<ConnectionManager<PgConnection>> {
19 | |     dotenv().ok();
20 | |
21 | |     let database_url = env::var("DATABASE_URL")
...  |
25 | |     Pool::new(config, manager).expect("Failed to create pool.")
26 | | }
   | |_^ the trait `diesel::connection::Connection` is not implemented for `diesel::PgConnection`
   |
   = note: required because of the requirements on the impl of `r2d2::ManageConnection` for `r2d2_diesel::ConnectionManager<diesel::PgConnection>`
   = note: required by `r2d2::Pool`

The online docs http://docs.diesel.rs/diesel/pg/struct.PgConnection.html states that the Connection trait is implemented by PgConnection.
I probably missing something.

My only Cargo.toml change (original line commented):
diesel = { git="https://github.com/diesel-rs/diesel", features = ["postgres"] }
#diesel = { version = "0.16.0", features = ["postgres"] }

[sgrif]

You will need to use [replace] in your Cargo.toml, it's not enough to just change your diesel line if you are using r2d2 or other plugins.

http://doc.crates.io/manifest.html#the-replace-section

[attdona]

I tried, but clearly I'm doing it in a wrong way ...

Cargo.toml:

[dependencies]
diesel = { version = "0.16.0", features = ["postgres"] }
...
[replace]
"diesel:0.16.0" = {git="https://github.com/diesel-rs/diesel"}

rustc output:

error[E0599]: no method named `load` found for type `diesel::query_builder::SelectStatement<information_schema::information_schema::key_column_usage::table, diesel::query_builder::select_clause::SelectClause<information_schema::information_schema::key_column_usage::columns::column_name>, diesel::query_builder::distinct_clause::NoDistinctClause, diesel::query_builder::where_clause::WhereClause<diesel::expression::operators::And<diesel::expression::operators::And<diesel::expression::array_comparison::In<information_schema::information_schema::key_column_usage::columns::constraint_name, diesel::expression::array_comparison::Subselect<diesel::query_builder::SelectStatement<information_schema::information_schema::table_constraints::table, diesel::query_builder::select_clause::SelectClause<information_schema::information_schema::table_constraints::columns::constraint_name>, diesel::query_builder::distinct_clause::NoDistinctClause, diesel::query_builder::where_clause::WhereClause<diesel::expression::operators::Eq<information_schema::information_schema::table_constraints::columns::constraint_type, diesel::expression::bound::Bound<diesel::types::Text, &str>>>>, diesel::types::Text>>, diesel::expression::operators::Eq<information_schema::information_schema::key_column_usage::columns::table_name, diesel::expression::bound::Bound<diesel::types::Text, &std::string::String>>>, diesel::expression::operators::Eq<information_schema::information_schema::key_column_usage::columns::table_schema, diesel::expression::bound::Bound<diesel::types::Text, std::string::String>>>>, diesel::query_builder::order_clause::OrderClause<information_schema::information_schema::key_column_usage::columns::ordinal_position>>` in the current scope
   --> /home/adona/.cargo/registry/src/github.com-1ecc6299db9ec823/diesel_infer_schema-0.16.0/src/information_schema.rs:156:10
    |
156 |         .load(conn)
    |          ^^^^
    |
    = note: the method `load` exists but the following trait bounds were not satisfied:
....

[sgrif]

Make sure you also point diesel_codegen and diesel_infer_schema at master

[attdona]

Ok, pointing at master also diesel_codegen and diesel_infer_schema it works as expected:

Just in case could help someone this is my setup (../diesel directory is the root of diesel github clone):

[dependencies]
diesel = {path = "../diesel/diesel", features = ["postgres"]}
diesel_infer_schema = {path = "../diesel/diesel_infer_schema", features = ["postgres"]}
diesel_codegen = {path = "../diesel/diesel_codegen", features = ["postgres"]}
[replace]
"diesel:0.16.0" = {path = "../diesel/diesel"}
"diesel_infer_schema:0.16.0" = {path = "../diesel/diesel_infer_schema"}
"diesel_codegen:0.16.0" = {path = "../diesel/diesel_codegen"}

@sgrif Thanks for your suggestions!