[feat] crates-io mirror environment config

[loynoir]

Problem

Let package manager env-configure-able is very convenient for scenario like

• docker

• devcontainer

.devcontainer/devcontainer.json

  "remoteEnv": {
    "NPM_CONFIG_REGISTRY": "http://self-hosted-verdaccio",

within container

$ npm config ls -l | grep verdaccio
registry = "http://self-hosted-verdaccio" 

But currently, cargo seems not env-configure-able, only accept .cargo/config.

Proposed Solution

Let cargo config env-configure-able.

Notes

No response

[weihanglo]

Configuring Cargo via environment variables is documented here: https://doc.rust-lang.org/cargo/reference/environment-variables.html#configuration-environment-variables. You can also set configuration via --config cli argument.

Is there something missing you're looking for specifically?

[loynoir]

Seems not working.

Expected

[source.crates-io]
replace-with = 'mirror'

[source.mirror]
registry = "sparse+https://mirror/crates.io-index/"

$ cargo build
...
    Updating `mirror` index
...

Actual

$ env \
    CARGO_REGISTRIES_MIRROR_INDEX="sparse+https://mirror/crates.io-index/" \
    CARGO_REGISTRY_DEFAULT="mirror" \
    cargo build
...
    Updating crates.io index
...

[Eh2406]

In your second example you set https://doc.rust-lang.org/cargo/reference/config.html#registrydefault but in the ferst you set https://doc.rust-lang.org/cargo/reference/config.html#sourcenamereplace-with witch do very difrent things. (despite the confusing naming, sorry.)

[weihanglo]

Also, as you may have read, a Cargo config value usually but not always has a counterpart of environment variable

Currently only integer, boolean, string and some array values are supported to be defined by environment variables. Descriptions below indicate which keys support environment variables and otherwise they are not supported due to technical issues.

Besides, there is a pretty unstable feature -Zadvanced-env tracked in #7406, which tries to fill the gap between config files and environment variables. I believe that also fixes your issue of setting source replacement via env, so closing in favor of #5416 and #7406.

Thank you for the report :)