Alternative handling of output paths

[NyxCode]

Hey @escritorio-gustavo!

This is an experiment to see if we can further simplify and streamline the handling of export paths.
Let's start with a practical example:

Example

Before

In the workspace E2E test, there's the parent crate, which depends on crate1.
The struct crate1::Crate1 has #[ts(export_to = "crate1/")], and
the struct parent::Parent has #[ts(export)].

When running cargo test, only parent::Parent exports, but it takes its dependency crate1::Crate1 with it.
That results in this directory structure:

parent/
    bindings/
        Parent.ts
    crate1/
        Crate1.ts

After

With this change, the resulting directory structure looks like this:

parent/
    bindings/
        Parent.ts
        crate1/
            Crate1.ts

Explanation

Before

For a type, the output path is
./{TS_RS_EXPORT_DIR}/bindings/{name}.ts if #[ts(export_to = "...")] is not specified and
./{TS_RS_EXPORT_DIR}/{name}.ts if #[ts(export_to = "...")] is specified.

This is because TS::EXPORT_TO defaults to bindings/{name.ts}, but changing it using #[ts(export_to = "...")] gets rid of the bindings/ prefix.
The environment variable TS_RS_EXPORT_DIR defaults to ..

After

With this change, it's the environment variable TS_RS_EXPORT_DIR which defaults to ./bindings.

Therefore, with this change, the output path is always ./{TS_RS_EXPORT_DIR}/{name}.ts.
We take the TS_RS_EXPORT_DIR (or ./bindings), append the name to it (or the #[ts(export_to = "...")] override), and we're done.

---

I feel like this behaviour better matches what users would expect. They specify where there files should go relative to some base directory, TS_RS_EXPORT_DIR.
What do you think?

[NyxCode]

Regarding the implementation: I moved output_path() into TS, and completely got rid of the const EXPORT_TO.

[NyxCode]

The implementation of that is super simple - Take TS_RS_EXPORT_DIR (or ./bindings), and append the name (or #[ts(export_to = "...")] override to it.

[NyxCode]

In our example, cargo test does the same as before:

example/
  bindings/
    ...

With TS_RS_EXPORT_DIR=./typescript, however, you'd get this:

example/
  typescript/
    bindings/
      ...

With this change, you'd get

example/
  typescript/
    ...

[NyxCode]

Before, renaming the file from Role.ts to UserRole.ts required adding the bindings/ prefix back again.
With this change, this is no longer necessary.

[escritorio-gustavo]

For a type, the output path is
./{TS_RS_EXPORT_DIR}/bindings/{name}.ts if #[ts(export_to = "...")] is not specified

Oof, this bindings is not supposed to be there, this is a major oversight from my part when doing #250, caused by the fact that all of our tests use #[ts(export_to = "...")], so I didn't even consider what would happen without it

[escritorio-gustavo]

After

With this change, it's the environment variable TS_RS_EXPORT_DIR which defaults to ./bindings.

Therefore, with this change, the output path is always ./{TS_RS_EXPORT_DIR}/{name}.ts. We take the TS_RS_EXPORT_DIR (or ./bindings), append the name to it (or the #[ts(export_to = "...")] override), and we're done.

Very nice way of dealing with it!

[NyxCode]

Alright, then I'll go ahead and merge this!
It is a breaking change, but it's probably a good time to do it.
All the tests, for example, have #[ts(export_to = "tests_out/")], so they end up in ts-rs/bindings/tests-out.

[escritorio-gustavo]

All the tests, for example, have #[ts(export_to = "tests_out/")]

We could make a separate PR to remove tests-out from the tests to reduce nesting