Cargo 是否可以在不构建应用程序的情况下下载和构建依赖项? [英] Can Cargo download and build dependencies without also building the application?

问题描述

有没有办法告诉 Cargo 安装和构建我的所有依赖项，但不要尝试构建我的应用程序?

Is there a way to tell Cargo to install and build all my dependencies, but not attempt to build my application?

我认为 cargo install 会这样做，但实际上它也一直用于构建我的应用程序.我想进入一种状态，其中 cargo build 会找到所有准备使用的依赖项，但不触及 /src 目录.

I thought cargo install would do that, but it actually goes all the way to building my app too. I want to get to a state where cargo build would find all dependencies ready to use, but without touching the /src directory.

我真正想要实现的目标:

我正在尝试为 Rust 应用程序构建 Docker 映像，我想在其中执行以下步骤:

I'm trying to build a Docker image for a Rust application, where I'd like to do the following steps:

构建时间(docker build .):

1. 导入安装了 rust 工具的 docker 镜像
2. 添加我的 Cargo.toml 和 Cargo.lock 文件
3. 下载并构建所有依赖项
4. 将我的源目录添加到图像中
5. 构建我的源代码

运行时间(docker run ...):

1. 运行应用程序

我已经尝试了以下 Dockerfile，但指示的步骤也构建了我的应用程序(由于源目录尚不存在，这当然失败了):

I've tried the following Dockerfile, but the indicated step builds my application as well (which of course fails since the source directory isn't there yet):

FROM jimmycuadra/rust

ADD Cargo.toml /source
ADD Cargo.lock /source

RUN cargo install # <-- failure here

ADD src /source/src
RUN cargo build

ENTRYPOINT cargo run

我想将安装依赖项步骤与实际构建我的应用程序分开的原因是，如果我不更改依赖项，我希望 Docker 能够使用已安装和构建的所有依赖项的缓存映像.因此，我不能ADD/src/source/src 直到之后安装依赖项，因为当我更改自己的代码时，这会使缓存的图像无效.

The reason I want to separate the install dependencies step from actually building my application, is that if I don't change the dependencies, I want Docker to be able use a cached image with all dependencies already installed and built. Thus, I can't ADD /src /source/src until after installing the dependecies, as that would invalidate the cached image when I change my own code.

推荐答案

据我所知，没有对仅在 Cargo 中构建依赖项的本地支持.有一个悬而未决的问题.如果你可以向 Cargo 提交一些东西来完成它，或者创建一个第三方 Cargo 插件，我不会感到惊讶.我也希望 cargo doc 有这个功能，当我自己的代码太坏而无法编译时;-)

There is no native support for building just the dependencies in Cargo, as far as I know. There is an open issue for it. I wouldn't be surprised if you could submit something to Cargo to accomplish it though, or perhaps create a third-party Cargo addon. I've wanted this functionality for cargo doc as well, when my own code is too broken to compile ;-)

但是，我维护的 Rust 游乐场 确实实现了您的最终目标.有一个 基础 Docker 容器，用于安装 Rustup 并复制到Cargo.toml 带有可用于游乐场的所有板条箱.构建步骤创建了一个空白项目(使用src/lib.rs)，然后调用 cargo build 和 cargo build --release 来编译 crate:

However, the Rust playground that I maintain does accomplish your end goal. There's a base Docker container that installs Rustup and copies in a Cargo.toml with all of the crates available for the playground. The build steps create a blank project (with a dummy src/lib.rs), then calls cargo build and cargo build --release to compile the crates:

RUN cd / && \
    cargo new playground
WORKDIR /playground

ADD Cargo.toml /playground/Cargo.toml
RUN cargo build
RUN cargo build --release
RUN rm src/*.rs

所有下载的 crate 都存储在 Docker 镜像的 $HOME/.cargo 目录中，所有构建的 crate 都存储在应用程序 target/{debug,release} 目录.

All of the downloaded crates are stored in the Docker image's $HOME/.cargo directory and all of the built crates are stored in the applications target/{debug,release} directories.

稍后，真正的源文件被复制到容器中，cargo build/cargo run 可以使用现在编译的 crate 再次执行.

Later on, the real source files are copied into the container and cargo build / cargo run can be executed again, using the now-compiled crates.

如果您正在构建一个可执行项目，您还需要在 Cargo.lock 中进行复制.

If you were building an executable project, you'd want to copy in the Cargo.lock as well.

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