feat: RustLsp explainError command

CHANGELOG.md

@@ -5,8 +5,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [Unreleased]
+## [3.1.0] - 2023-10-28
 ### Added
+- `:RustLsp explainErrors` command, uses `rustc --explain` on error diagnostics with
+  an error code.
 - `:RustLsp rebuildProcMacros` command.
 
 ## [3.0.4] - 2023-10-25

README.md

@@ -244,6 +244,25 @@ for more configuration options.
   ```
 </details>
 
+<details>
+  <summary>
+	<b>Explain errors</b>
+  </summary>
+
+  Display a hover window with explanations from the [rust error codes index](https://doc.rust-lang.org/error_codes/error-index.html)
+  over error diagnostics (if they have an error code).
+
+  ```vimscript
+  :RustLsp explainError
+  ```
+  ```lua
+  vim.cmd.RustLsp('explainError')
+  ```
+
+![](https://github.com/mrcjkb/rustaceanvim/assets/12857160/bac9b31c-22ca-40c4-bfd3-b8c5ba4cc49a)
+
+</details>
+
 <details>
   <summary>
 	<b>Open Cargo.toml</b>

lua/rustaceanvim/commands/explain_error.lua

@@ -0,0 +1,70 @@
+local M = {}
+
+local rustc = 'rustc'
+
+function M.explain_error()
+  if vim.fn.executable(rustc) ~= 1 then
+    vim.notify('rustc is needed to explain errors.', vim.log.levels.ERROR)
+    return
+  end
+
+  local diagnostics = vim.tbl_filter(function(diagnostic)
+    return diagnostic.code ~= nil and diagnostic.source == 'rustc'
+  end, vim.diagnostic.get(0, {}))
+  if #diagnostics == 0 then
+    vim.notify('No explainnable errors found.', vim.log.levels.INFO)
+    return
+  end
+  local win_id = vim.api.nvim_get_current_win()
+  local opts = {
+    cursor_position = vim.api.nvim_win_get_cursor(win_id),
+    severity = vim.diagnostic.severity.ERROR,
+    wrap = true,
+  }
+  local found = false
+  local diagnostic
+  local pos_map = {}
+  local pos_id = 1
+  repeat
+    diagnostic = vim.diagnostic.get_next(opts)
+    pos_map[pos_id] = diagnostic
+    if diagnostic == nil then
+      break
+    end
+    found = diagnostic.code ~= nil and diagnostic.source == 'rustc'
+    local pos = { diagnostic.lnum, diagnostic.col }
+    pos_id = pos[1] + pos[2]
+    opts.cursor_position = pos
+    local searched_all = pos_map[pos_id] ~= nil
+  until diagnostic == nil or found or searched_all
+  if not found then
+    return
+  end
+
+  ---@param sc vim.SystemCompleted
+  local function handler(sc)
+    if sc.code ~= 0 or not sc.stdout then
+      vim.notify('Error calling rustc --explain' .. (sc.stderr and ': ' .. sc.stderr or ''), vim.log.levels.ERROR)
+      return
+    end
+    local output = sc.stdout:gsub('```', '```rust', 1)
+    local markdown_lines = vim.lsp.util.convert_input_to_markdown_lines(output, {})
+    vim.schedule(function()
+      vim.lsp.util.open_floating_preview(markdown_lines, 'markdown', {
+        focus = false,
+        focusable = true,
+        focus_id = 'rustc-explain-error',
+        close_events = { 'CursorMoved', 'BufHidden', 'InsertCharPre' },
+      })
+    end)
+  end
+
+  -- Save position in the window's jumplist
+  vim.cmd("normal! m'")
+  vim.api.nvim_win_set_cursor(win_id, { diagnostic.lnum + 1, diagnostic.col })
+  -- Open folds under the cursor
+  vim.cmd('normal! zv')
+  vim.system({ rustc, '--explain', diagnostic.code }, nil, vim.schedule_wrap(handler))
+end
+
+return M.explain_error

lua/rustaceanvim/commands/init.lua

@@ -27,6 +27,9 @@ local command_tbl = {
   expandMacro = function(_)
     require('rustaceanvim.commands.expand_macro')()
   end,
+  explainError = function(_)
+    require('rustaceanvim.commands.explain_error')()
+  end,
   rebuildProcMacros = function()
     require('rustaceanvim.commands.rebuild_proc_macros')()
   end,

lua/rustaceanvim/health.lua

@@ -81,6 +81,20 @@ local external_dependencies = {
       Not required in standalone files.
     ]],
   },
+  {
+    name = 'rustc',
+    get_binaries = function()
+      return { 'rustc' }
+    end,
+    optional = function()
+      return true
+    end,
+    url = '[rustc](https://doc.rust-lang.org/rustc/what-is-rustc.html)',
+    info = [[
+      The Rust compiler.
+      Called by `:RustLsp explainError`.
+    ]],
+  },
   {
     name = config.dap.adapter.command,
     get_binaries = function()

lua/rustaceanvim/hover_actions.lua

@@ -83,7 +83,7 @@ function M.handler(_, result, ctx)
     'markdown',
     vim.tbl_extend('keep', config.tools.hover_actions, {
       focusable = true,
-      focus_id = 'rust-tools-hover-actions',
+      focus_id = 'rust-analyzer-hover-actions',
       close_events = { 'CursorMoved', 'BufHidden', 'InsertCharPre' },
     })
   )