.env Support for Repositories with Multiple Crates

[xyzd0]

SQLx version: 0.3.4

Current Behaviour

If I have a repository with multiple crates, and a root Cargo.toml file defining each crate as a workspace, SQLx won't pick up .env files for specific crates, it will only pick this up from the project root directory.

This is not ideal as if for example, multiple microservices were being developed in a "monorepo", each one using its own database and .env file, SQLx will only attempt to use an .env file defined at the project root directory. For example,

.
├── .env  # Only this .env file is read and is used across all crates
├── Cargo.toml
├── README.md
├── target
│   ├── debug
├── microservice1
│   ├── server
│   │   ├── Cargo.toml
│   │   └── src
│   │       ├── file.rs
│   └── tests
│       ├── Cargo.toml
│       └── src
│           └── main.rs
├── microservice2
│   ├── server
│   │   ├── Cargo.toml
│   │   └── src
│   │       ├── file.rs
│   └── tests
│       ├── Cargo.toml
│       └── src
│           └── main.rs

Preferred Behaviour

It would be better if SQLx was able to pick up .env files from each crate in the project, using the crate specific DATABASE_URL for compile-time query validation.

For example,

.
├── Cargo.toml
├── README.md
├── target
│   ├── debug
├── microservice1
│   ├── server
│   │   ├── .env  # DATABASE_URL=postgres://microservice1_db
│   │   ├── Cargo.toml
│   │   └── src
│   │       ├── file.rs
│   └── tests
│       ├── Cargo.toml
│       └── src
│           └── main.rs
├── microservice2
│   ├── server
│   │   ├── .env  # DATABASE_URL=postgres://microservice2_db
│   │   ├── Cargo.toml
│   │   └── src
│   │       ├── file.rs
│   └── tests
│       ├── Cargo.toml
│       └── src
│           └── main.rs

[abonander]

Yeah, currently we just rely on the implicit behavior of dotenv to load the .env file from the current working directory.

This is easy to fix if we load relative to CARGO_MANIFEST_DIR.

However, I can see this being perhaps a breaking change for some people. We should probably try CARGO_MANIFEST_DIR first and then fall back to the current working directory.

[abonander]

Wait... version 0.15.0? We're on 0.3.4. Did you give the version number for a different crate by mistake?

[xyzd0]

Hah yep apologies, that was a different crate! Updated the issue body.

[jsdw]

As a workaround until this is merged, you can use a small build.rs file in crates to set a different DATABASE_URL env var for each one. For example, Add a build.rs that contains something like this to each crate you want a different DATABASE_URL for:

fn main() {
    println!("cargo:rustc-env=DATABASE_URL=postgres://user:pass@localhost/dbname")
}