[unstable option] struct_field_align_threshold

[scampi]

Tracking issue for unstable option: struct_field_align_threshold

[jmillikin]

Two issues I've noticed with this option:

First, it interacts poorly with hard_tabs. The + lines ought to be tabbed equal to len and then space-aligned afterward, but they're being given block indentation instead. Users with different tab lengths will see weird formatting.

This might be easier to visualize by copying the following examples to an editor with space highlighting.

Bad:

	.push_sized(&fuse_kernel::fuse_out_header {
		len:    (size_of::<fuse_kernel::fuse_out_header>()
			+ fuse_kernel::FUSE_COMPAT_ENTRY_OUT_SIZE
			+ size_of::<fuse_kernel::fuse_open_out>()) as u32,
		error:  0,
		unique: REQUEST_ID,
	})

Would be good:

	.push_sized(&fuse_kernel::fuse_out_header {
		len:    (size_of::<fuse_kernel::fuse_out_header>()
		         + fuse_kernel::FUSE_COMPAT_ENTRY_OUT_SIZE
		         + size_of::<fuse_kernel::fuse_open_out>()) as u32,
		error:  0,
		unique: REQUEST_ID,
	})

---

Secondly, I don't think block-formatted literals should be aligned -- or it should maybe be disable-able. This is how gofmt does it, and it is easier to read when working with mixed primitives and compound literals.

Example of poor formatting:

  .push_sized(&fuse_kernel::fuse_entry_out {
    // ...
    entry_valid_nsec: 0,
    attr_valid_nsec:  0,
    attr:             fuse_kernel::fuse_attr {
      ino: 11,
      ..Default::default()
    },
  })

What I would expect:

  .push_sized(&fuse_kernel::fuse_entry_out {
    // ...
    entry_valid_nsec: 0,
    attr_valid_nsec:  0,
    attr: fuse_kernel::fuse_attr {
      ino: 11,
      ..Default::default()
    },
  })

[SOF3]

Is there a similar option for function parameters?

[wusticality]

Will this ever be made available in stable Rust?

[ytmimi]

@wusticality please see https://github.com/rust-lang/rustfmt/discussions/5365

[theon]

Thanks for adding this option. An issue I have noticed whilst using it is that the formatting isn't applied when using ..Default::default(). For example, I get:

StandardMaterial {
    base_color_texture: Some(asset_server.load("textures/card_back.png")),
    cull_mode: Some(Face::Front),
    fog_enabled: false,
    unlit: true,
    alpha_mode: AlphaMode::Blend,
    ..Default::default()
}

whereas I would expect:

StandardMaterial {
    base_color_texture: Some(asset_server.load("textures/card_back.png")),
    cull_mode:          Some(Face::Front),
    fog_enabled:        false,
    unlit:              true,
    alpha_mode:         AlphaMode::Blend,
    ..Default::default()
}

[ytmimi]

@theon thanks for sharing. When you have a chance can you create a new issue outlining the problem in more detail. I think it would be best to track this in a separate thread.

[theon]

Thanks @ytmimi, I have raised https://github.com/rust-lang/rustfmt/issues/6080