Is it possible to customize the code generation to prepend code?

[JasterV]

I have the following Cargo.toml in my project:

[package]
name = "my-project"
version = "0.1.0"
edition = "2024"

[features]
default = ["tonic_0_14"]

tonic_0_12 = [
  "dep:prost-build",
  "dep:prost-types_0_13",
  "dep:prost_0_13",
  "dep:tonic-build_0_12",
  "dep:tonic_0_12",
]

tonic_0_13 = [
  "dep:prost-build",
  "dep:prost-types_0_13",
  "dep:prost_0_13",
  "dep:tonic-build_0_13",
  "dep:tonic_0_13",
]

tonic_0_14 = [
  "dep:prost-types_0_14",
  "dep:prost_0_14",
  "dep:tonic-build_0_14",
  "dep:tonic-prost-build",
  "dep:tonic_0_14",
]

[dependencies]
bytes = "1"

prost_0_13 = { package = "prost", version = "0.13", optional = true }
prost_0_14 = { package = "prost", version = "0.14", optional = true }

prost-types_0_13 = { package = "prost-types", version = "0.13", optional = true }
prost-types_0_14 = { package = "prost-types", version = "0.14", optional = true }

tonic_0_12 = { package = "tonic", version = "0.12", optional = true }
tonic_0_13 = { package = "tonic", version = "0.13", optional = true }
tonic_0_14 = { package = "tonic", version = "0.14", optional = true }

tonic-prost = { version = "0.14", optional = true }

[build-dependencies]
prost-build = { version = "0.13", optional = true }

tonic-build_0_12 = { package = "tonic-build", version = "0.12", optional = true }
tonic-build_0_13 = { package = "tonic-build", version = "0.13", optional = true }
tonic-build_0_14 = { package = "tonic-build", version = "0.14", optional = true }

tonic-prost-build = { version = "0.14", optional = true }

I am doing this because I need the users to be able to use tonic in different versions. (Some use tonic 0.12, some use tonic 0.13, and they are legacy applications so its difficult to update the dependencies)

The problem is that when generating the code, it doesn't compile because the generated code has references to tonic:: and prost_types:: but those dependencies don't exist anymore, they are renamed to tonic_0_x, prost-types_0_x

This could be solved by injecting a use tonic_0_14 as tonic in every module.

Is there a way to customize the code generation this way?

[LucioFranco]

I think a better solution would be to provide a way to have the codegen use custom names for the crates. I would accept a PR for this if you're interested in the work. We also want to route the crates to pull from tonic-prost::prost rather than requiring the use to also import that library.