[Feature Request] Minimize dependencies

[weiznich]

🚀 Feature Request

Motivation

cargo tree currently reports the following dependencies for serde-generate:

serde-generate v0.24.0
├── bcs v0.1.4
│   ├── serde v1.0.148
│   │   └── serde_derive v1.0.148 (proc-macro)
│   │       ├── proc-macro2 v1.0.47
│   │       │   └── unicode-ident v1.0.5
│   │       ├── quote v1.0.21
│   │       │   └── proc-macro2 v1.0.47 (*)
│   │       └── syn v1.0.104
│   │           ├── proc-macro2 v1.0.47 (*)
│   │           ├── quote v1.0.21 (*)
│   │           └── unicode-ident v1.0.5
│   └── thiserror v1.0.37
│       └── thiserror-impl v1.0.37 (proc-macro)
│           ├── proc-macro2 v1.0.47 (*)
│           ├── quote v1.0.21 (*)
│           └── syn v1.0.104 (*)
├── bincode v1.3.3
│   └── serde v1.0.148 (*)
├── heck v0.3.3
│   └── unicode-segmentation v1.10.0
├── include_dir v0.6.2
│   ├── glob v0.3.0
│   ├── include_dir_impl v0.6.2 (proc-macro)
│   │   ├── anyhow v1.0.66
│   │   ├── proc-macro-hack v0.5.19 (proc-macro)
│   │   ├── proc-macro2 v1.0.47 (*)
│   │   ├── quote v1.0.21 (*)
│   │   └── syn v1.0.104 (*)
│   └── proc-macro-hack v0.5.19 (proc-macro)
├── maplit v1.0.2
├── phf v0.10.1
│   ├── phf_macros v0.10.0 (proc-macro)
│   │   ├── phf_generator v0.10.0
│   │   │   ├── phf_shared v0.10.0
│   │   │   │   └── siphasher v0.3.10
│   │   │   └── rand v0.8.5
│   │   │       ├── libc v0.2.137
│   │   │       ├── rand_chacha v0.3.1
│   │   │       │   ├── ppv-lite86 v0.2.17
│   │   │       │   └── rand_core v0.6.4
│   │   │       │       └── getrandom v0.2.8
│   │   │       │           ├── cfg-if v1.0.0
│   │   │       │           └── libc v0.2.137
│   │   │       └── rand_core v0.6.4 (*)
│   │   ├── phf_shared v0.10.0 (*)
│   │   ├── proc-macro-hack v0.5.19 (proc-macro)
│   │   ├── proc-macro2 v1.0.47 (*)
│   │   ├── quote v1.0.21 (*)
│   │   └── syn v1.0.104 (*)
│   ├── phf_shared v0.10.0 (*)
│   └── proc-macro-hack v0.5.19 (proc-macro)
├── serde v1.0.148 (*)
├── serde-reflection v0.3.6
│   ├── once_cell v1.16.0
│   ├── serde v1.0.148 (*)
│   └── thiserror v1.0.37 (*)
├── serde_bytes v0.11.8
│   └── serde v1.0.148 (*)
├── serde_yaml v0.8.26
│   ├── indexmap v1.9.2
│   │   └── hashbrown v0.12.3
│   │   [build-dependencies]
│   │   └── autocfg v1.1.0
│   ├── ryu v1.0.11
│   ├── serde v1.0.148 (*)
│   └── yaml-rust v0.4.5
│       └── linked-hash-map v0.5.6
├── structopt v0.3.26
│   ├── clap v2.34.0
│   │   ├── ansi_term v0.12.1
│   │   ├── atty v0.2.14
│   │   │   └── libc v0.2.137
│   │   ├── bitflags v1.3.2
│   │   ├── strsim v0.8.0
│   │   ├── textwrap v0.11.0
│   │   │   └── unicode-width v0.1.10
│   │   ├── unicode-width v0.1.10
│   │   └── vec_map v0.8.2
│   ├── lazy_static v1.4.0
│   └── structopt-derive v0.4.18 (proc-macro)
│       ├── heck v0.3.3 (*)
│       ├── proc-macro-error v1.0.4
│       │   ├── proc-macro-error-attr v1.0.4 (proc-macro)
│       │   │   ├── proc-macro2 v1.0.47 (*)
│       │   │   └── quote v1.0.21 (*)
│       │   │   [build-dependencies]
│       │   │   └── version_check v0.9.4
│       │   ├── proc-macro2 v1.0.47 (*)
│       │   ├── quote v1.0.21 (*)
│       │   └── syn v1.0.104 (*)
│       │   [build-dependencies]
│       │   └── version_check v0.9.4
│       ├── proc-macro2 v1.0.47 (*)
│       ├── quote v1.0.21 (*)
│       └── syn v1.0.104 (*)
└── textwrap v0.13.4
    ├── smawk v0.3.1
    └── unicode-width v0.1.10

Ideally serde-generate would provide an API that put dependencies behind different feature flags, so that not everything is required if only a small part of the crate is used.

Especially that includes the following dependencies:

• structopt as that's not needed if serde-generate is used as dependency
• bcs and bincode as sometimes you want to use one or the other
• serde_yaml as it's not always required to build a yaml representation of the corresponding types

I'm not sure about other dependencies like textwrap, heck, serde_bytes, include_dir, maplit and phf.

Pitch

Describe the solution you'd like Put parts of the API behind feature flags, so that users can choose what to use + what gate corresponding dependencies on these flags.

Describe alternatives you've considered

Do not change anything and pull in potentially unneeded dependencies.

Are you willing to open a pull request? (See CONTRIBUTING)

I would be willing to contribute a PR for that

Additional context

[kturney]

Minimizing deps would be great!

A few things I think could be interesting to consider:

• split the cli/bin of serde-generate into a separate package like bindgen did recently https://github.com/rust-lang/rust-bindgen/blob/main/CHANGELOG.md#0610
• split each language into a separate workspace package and include into serde-generate via feature
• put the test-utils behind a feature

[weiznich]

@kturney I filled #30 with the necessary changes.

[ma2bd]

I am supportive of splitting the library and the binary as well as feature-gating test-util.

What is the rational for creating a crate for each language though? As far as cargo is concerned, each of them is a single source file (with no language-specific dependency crate, most likely). Is it about the size of the library due to included data blobs? Or is it just for versioning purposes?

@kturney @weiznich

[kturney]

Pros:

• reduced build times
• ability for each language package to add deps without needing to include that dep for all languages

Cons:

• more packages to manage
• maybe absolute build time reduction is minimal

Maybe just splitting the library and binary would get us 80% of the benefits? It just sounds conceptually nice to me for each language and runtime to be given its own package.

[weiznich]

What is the rational for creating a crate for each language though?

I just more or less blindly implemented the proposal from @kturney. There is no special reasoning from my side here.

[ma2bd]

In the short term, I would prefer to only split the library and the binary to minimize the disruption for other users. I'm also ok to introduce feature flags for each language (defaulting to all of them).

[weiznich]

@ma2bd I've updated the PR to follow your suggestions.