"Add #[derive]" missing from code actions with rust-analyzer

[miikkas]

Bug description
Code actions for structs don't have the "Add `#[derive]`" item, which used to be available when using older versions of rust-analyzer. The "Add `#[derive]`" item is available in vscode, though, but I can't seem to get it to appear in Emacs even when using the same version of rust-analyzer as with vscode.

To reproduce

1. cargo new lsp-ra-bug-repro
2. Use the following code for lsp-ra-bug-repro/src/main.rs:

   struct WantToPrint {
       x: i32,
       y: i32,
   }
   
   fn main() {
       let wtp = WantToPrint { x: 1234, y: 5678, };
       println!("{:?}", wtp);
   }

3. Move cursor/caret to the beginning of the first line
4. Invoke lsp-mode's execution of code actions (I pressed C-c l a a having configured it thus)
5. An option to "Add `#[derive]`" is missing. Here's how it appears in a very bare-bones Emacs with only rust-mode and lsp-mode manually installed, after pressing TAB a couple of times after the previous step:
   
6. Additionally, pressing RET here gives the error "Wrong type argument: hash-table-p, nil". I don't remember this happening when using an older version of rust-analyzer, but I suppose it's somehow linked to how I seem to get an empty(?) item at the beginning of the minibuffer when using Ido mode on my default configuration. Here's how the empty item looks in that case – the { | at the beginning without any text between those characters, none of the actually usable code actions being currently selected:
   
   To be clear, pressing RET on that empty item in Ido mode will also yield the same wrong type argument error message.

Expected behavior
An option to "Add `#[derive]`" should be available. Here's how it appears in vscode (the item is highlighted because I had my mouse cursor on it, which isn't visible in the screenshot):

Environment
OS: Ubuntu 20.04
Emacs: GNU Emacs 26.3 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.14) of 2020-03-26, modified by Debian
lsp-mode: 20200713.506 from MELPA (I've also tested on several other versions during the past month)
rust-analyzer: 5ca7cd9 (included with vscode), 4b1c372 (manually built today, 2020-07-13), also several others during the past month

LSP Mode workspace log
I captured this workspace log from pressing C-c l a a with the above file open and the cursor where stated in the above reproduction instructions.

[yyoncho]

Thank you for detailed report, I will take a look.

[yyoncho]

@flodiebold I spent quite some time looking into this issue and in rust analyzer code and it seems like RA is just failing on calculating this quick fix and it is related to something else...

[flodiebold]

I think the code action isn't generated because lsp-mode doesn't support the snippet TextEdit extension yet. Most code actions just return a non-snippet edit in that case, but this one doesn't generate, probably because it doesn't make that much sense if it can't position the cursor.

[yyoncho]

I think the code action isn't generated because lsp-mode doesn't support the snippet TextEdit extension yet. Most code actions just return a non-snippet edit in that case, but this one doesn't generate, probably because it doesn't make that much sense if it can't position the cursor.

Thank you for the pointer, I will add support for that.

[yyoncho]

proposed fix at #1926

[miikkas]

I was traveling and couldn't get back to you immediately – thanks for working on this. I just tested yyoncho's proposed fix: I first upgraded lsp-mode to the latest version 20200716.2052 on MELPA, deleted the .elc files and replaced the three files changed in the pull request. I then went through the same steps I originally reported for reproducing the issue. Looks like I'm still not getting the option for adding #[derive], though.

[yyoncho]

@miikkas seems like melpa is not picking lsp-mode, the fix was submitted on 0717 but still there is no lsp-mode version with these changes.

[miikkas]

Sorry, I actually meant I applied your patch manually to the latest lsp-mode at the moment of writing my previous comment.

@miikkas seems like melpa is not picking lsp-mode, the fix was submitted on 0717 but still there is no lsp-mode version with these changes.

Looks like MELPA just finished with the latest update, and lsp-mode 20200718.1111 is now up.

I tried that version now, but the code action for adding #[derive] still wasn't available. I dug around the workspace log from around where rust-analyzer is started and noticed the following under the "capabilities" section:

    "experimental": {
      "snippetTextEdit": [
        ",",
        "lsp-enable-snippet"
      ]
    }

Seems like the lsp-enable-snippet variable is not evaluated here:

lsp-mode/lsp-rust.el

Line 572 in 52d5c94

:custom-capabilities '((experimental . ((snippetTextEdit . ,lsp-enable-snippet ))))))

I tried changing ,lsp-enable-snippet to t instead and the code action became available. Thanks for adding the feature! I don't know enough elisp, however, to fix it such that it would use that variable. :)

[kiennq]

@miikkas You just need to change the first quote ' into back-quote `

[yyoncho]

@miikkas sorry about that, I pushed a fix about that - I changed t to lsp-enable-snippet just before pushing which is not expanded.

[miikkas]

@miikkas sorry about that, I pushed a fix about that - I changed t to lsp-enable-snippet just before pushing which is not expanded.

Thank you!