Add getter/setter assists

[yoshuawuyts]

This patch makes progress towards the design outlined in #5943, and includes a small refactor which closes #7607. All together this patch does 4 things:

• Adds a generate_getter assist.
• Adds a generate_getter_mut assist.
• Adds a generate_setter assist.
• Moves the generate_impl_text function from generate_new into utils (which closes generate_enum_match doesn't work with generic params #7607).

Design Notes

I've chosen to follow the Rust API guidelines on getters as closely as possible. This deliberately leaves "builder pattern"-style setters out of scope.

Also, similar to #7570 this assist generates doc comments. I think this should work well in most cases, and for the few where it doesn't it's probably easily edited. This makes it slightly less correct than the #7570 implementation, but I think this is still useful enough to include for many of the same reasons.

The reason why this PR contains 3 assists, rather than 1, is because each of them is so similar to the others that it felt more noisy to do them separately than all at once. The amount of code added does not necessarily reflect that, but hope that still makes sense.

Examples

Input

struct Person {
    name: String,     // <- cursor on "name"
}

generate getter

struct Person {
    name: String,
}

impl Person {
    /// Get a reference to the person's name.
    fn name(&self) -> &String {
        &self.name
    }
}

generate mut getter

struct Person {
    name: String,
}

impl Person {
    /// Get a mutable reference to the person's name.
    fn name_mut(&mut self) -> &mut String {
        &mut self.name
    }
}

generate setter

struct Person {
    name: String,
}

impl Person {
    /// Set the person's name.
    fn set_name(&mut self, name: String) {
        self.name = name;
    }
}

[Veykril]

These do indeed share some common code like looking up the field the cursor is on and such, I wonder if it would make sense to put all of these assists in one module and extract those common bits into small helper functions. @matklad probably has a better eye for this.

[yoshuawuyts]

I wonder if it would make sense to put all of these assists in one module and extract those common bits into small helper functions

About 2/3rds of the file for each of these assists are tests and docs. The few bits which are for a large part just the template generation. I suspect it may be easier to keep them separate and possibly merge later than the other way around. It's unclear how #5943 will be implemented in the future, so at least for now keeping things separate may be the easiest to work with?

[Veykril]

Sounds good to me 👍
bors r+

[bors]

Build succeeded:

• Rust (macos-latest)
• Rust (ubuntu-latest)
• Rust (windows-latest)
• TypeScript (ubuntu-latest)
• TypeScript (windows-latest)

[Veykril]

[matklad]

Feels like we generate a bit too much assits here:

Let's fold all free into one "generate getter/setter" and use an "assist group" for that. (see, eg, convert_integer_literal)

[Veykril]

Gif of the assists after #7662

[nicraMarcin]

Hi,
is it possible to generate all fields?

[JonasRothmann]

It seems to not work if the impl has a macro

pub struct Account {
  pub id: String,
  pub user_id: String,
  pub provider: String,
}

#[juniper::graphql_object(Context = Context)]
impl Account {
    
    pub fn id(&self) -> &str {
        self.id.as_ref()
    }

    pub fn user_id(&self) -> &str {
        self.user_id.as_ref()
    }
}

When I generate getters/setters it creates a new impl instead of adding to the existing one:

pub struct Account {
  pub id: String,
  pub user_id: String,
  pub provider: String,
}

impl Account {
    pub fn provider(&self) -> &str {
        self.provider.as_ref()
    }
}

#[juniper::graphql_object(Context = Context)]
impl Account {
    
    pub fn id(&self) -> &str {
        self.id.as_ref()
    }

    pub fn user_id(&self) -> &str {
        self.user_id.as_ref()
    }
}