Trying to build a reproducible environment with Nix about evcxr HOT 14 CLOSED

Hey, it works! (With a cargo vendor directory and manual :dep calls.)

Also works with only the single :dep rand call.

Also works when I switch to the Nix-produced vendor dir. 🎉

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One more question if you don't mind -- is there any actual difference between init.evcxr and prelude.rs ? I can't really tell from the docs. It seems you can put : directives in either one. And they seem to both get executed after you input the first command in the evcxr session?

There used to be a difference, but there isn't anymore. init.evcxr used to only contain commands that were executed one at a time, whereas prelude.rs contained code that was executed afterwards. But now they're basically the same. You're right that the docs on this could probably use some cleaning up.

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Awesome, thanks so much!

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P.S. In case it's relevant, I'm also setting CARGO_HOME to a directory with the original Cargo.toml/Cargo.lock, as well as a .cargo/config.toml file with some extra Cargo config like this:

[source.crates-io]
replace-with = "vendored-sources"

[source.vendored-sources]
local-registry = "/nix/store/.../some/index/path"

[net]
offline = true

from evcxr.

To debug this, I'd suggest setting EVCXR_TMPDIR=$HOME/tmp/e1 (or something like that), then running evcxr. Once it fails, cd $EVCXR_TMPDIR and try doing a cargo build to see if it gives the same error. If it does, you can try editing Cargo.toml to see what would be required to make it succeed.

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Something else I should mention is that adding lots of :dep commands will make evcxr startup pretty slow, since it will compile them all each time it starts - also rust-analzyer will analyse them all each time evcxr starts.

If you're specifying a custom local registry, do you need to specify the path to the package? Assuming there's only one version in the registry, I'd expect that you could just write:

:dep rand
rand::random::<u8>()

from evcxr.

Thanks for the quick response! I tried the EVCXR_TMPDIR thing and examined the Cargo.toml after each step. After the first few deps (cfg-if, wasi, and libc) they're all present:

[package]
name = "ctx"
version = "1.0.0"
edition = "2021"

[lib]
crate-type = ["cdylib"]
path = "src/lib.rs"

[profile.dev]
opt-level = 2
debug = false
rpath = true
lto = false
debug-assertions = true
codegen-units = 16
panic = 'unwind'
incremental = true
overflow-checks = true

[dependencies]
wasi = { path = "/nix/store/44d4b4533ydszs27h6488w39sg3m7ivb-cargo-vendor-dir/wasi-0.11.0+wasi-snapshot-preview1" }
libc = { path = "/nix/store/44d4b4533ydszs27h6488w39sg3m7ivb-cargo-vendor-dir/libc-0.2.145" }
cfg-if = { path = "/nix/store/44d4b4533ydszs27h6488w39sg3m7ivb-cargo-vendor-dir/cfg-if-1.0.0" }

Then, after trying to add getrandom, the Cargo.toml changes abruptly and the other dependencies disappear:

    [package]
    name = "evcxr_dummy_validate_dep"
    version = "0.0.1"
    edition = "2021"

    [lib]
    path = "lib.rs"

    [dependencies]
    getrandom = { path = "/nix/store/44d4b4533ydszs27h6488w39sg3m7ivb-cargo-vendor-dir/getrandom-0.2.9" }

Reading between the lines here... is it possible that evcxr is doing a "validation step" on each :dep call where it produces a Cargo.toml package called evcxr_dummy_validate_dep with only that dependency? And then only if that succeeds does it add the dependency to the main file with package name ctx?

If you're specifying a custom local registry, do you need to specify the path to the package?

I hope I can get it to work that way. I'll definitely try, probably after the basics are working with manual :dep calls.

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Btw, would evcxr work with normal cargo vendor output instead? It produces output like this:

   Vendoring cfg-if v1.0.0 (/home/tom/.cargo/registry/src/github.com-1ecc6299db9ec823/cfg-if-1.0.0) to /tmp/vendor2/cfg-if
   Vendoring getrandom v0.2.10 (/home/tom/.cargo/registry/src/github.com-1ecc6299db9ec823/getrandom-0.2.10) to /tmp/vendor2/getrandom
   Vendoring libc v0.2.147 (/home/tom/.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.147) to /tmp/vendor2/libc
   Vendoring ppv-lite86 v0.2.17 (/home/tom/.cargo/registry/src/github.com-1ecc6299db9ec823/ppv-lite86-0.2.17) to /tmp/vendor2/ppv-lite86
   Vendoring rand v0.8.5 (/home/tom/.cargo/registry/src/github.com-1ecc6299db9ec823/rand-0.8.5) to /tmp/vendor2/rand
   Vendoring rand_chacha v0.3.1 (/home/tom/.cargo/registry/src/github.com-1ecc6299db9ec823/rand_chacha-0.3.1) to /tmp/vendor2/rand_chacha
   Vendoring rand_core v0.6.4 (/home/tom/.cargo/registry/src/github.com-1ecc6299db9ec823/rand_core-0.6.4) to /tmp/vendor2/rand_core
   Vendoring wasi v0.11.0+wasi-snapshot-preview1 (/home/tom/.cargo/registry/src/github.com-1ecc6299db9ec823/wasi-0.11.0+wasi-snapshot-preview1) to /tmp/vendor2/wasi
To use vendored sources, add this to your .cargo/config.toml for this project:

[source.crates-io]
replace-with = "vendored-sources"

[source.vendored-sources]
directory = "/tmp/vendor2"

I've tried to get this working by setting EVCXR_CONFIG_DIR to point to a file with these configs, but no luck so far.

from evcxr.

Reading between the lines here... is it possible that evcxr is doing a "validation step" on each :dep call where it produces a Cargo.toml package called evcxr_dummy_validate_dep with only that dependency? And then only if that succeeds does it add the dependency to the main file with package name ctx?

Yep, that's exactly what it does. The code that does that is here.

I assume when you cargo build in $EVCXR_TMPDIR that it fails to build? Assuming the failure is that it can't find cfg-if, any idea why? Given that cfg-if is in the vendored-sources, I would have hoped that it would find it.

I've tried to get this working by setting EVCXR_CONFIG_DIR to point to a file with these configs, but no luck so far.

EVCXR_CONFIG_DIR is where evcxr looks for its config (e.g. init.evcxr) and doesn't affect where cargo looks for its config.

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EVCXR_CONFIG_DIR is where evcxr looks for its config (e.g. init.evcxr) and doesn't affect where cargo looks for its config.

Oh I misspoke, I meant I set CARGO_HOME to a directory with those configs.

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Oh I misspoke, I meant I set CARGO_HOME to a directory with those configs.

Ah, gotcha. Does setting CARGO_HOME to point to those configs make it work when you cargo build in EVCXR_TMPDIR?

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Does setting CARGO_HOME to point to those configs make it work when you cargo build in EVCXR_TMPDIR?

I'm working on that now. I'm actually not seeing any sign that cargo is picking up the configs at all, since it seems not to notice the net.offline flag. I must be setting it up wrong somehow...

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Argh, it was supposed to be $CARGO_HOME/config.toml instead of $CARGO_HOME/.cargo/config.toml :P

Okay, making progress now.

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I'm slightly amazed it worked on the Nix vendor dir, because the folder name format is different (cfg-if-1.0.0 vs. cfg-if).

But I'm happy, thanks for the help!

One more question if you don't mind -- is there any actual difference between init.evcxr and prelude.rs ? I can't really tell from the docs. It seems you can put : directives in either one. And they seem to both get executed after you input the first command in the evcxr session?

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