feat(nvim): show the pull request beside a diff prs opened

.pre-commit-config.yaml

@@ -423,6 +423,17 @@ repos:
         files: ^(configs/|shell/)
         stages: [pre-commit]
 
+      # The nvim config's Lua, each spec driven in a headless Neovim. A spec
+      # loads the plugins lazy installed, and passes saying SKIP on a machine
+      # where nvim has not started yet, so lazy installed none.
+      - id: nvim-specs
+        name: nvim specs (headless Neovim)
+        entry: task test:nvim
+        language: system
+        pass_filenames: false
+        files: ^(configs/common/\.config/nvim/|tests/nvim/)
+        stages: [pre-commit]
+
       # Tests a broken run would satisfy: every assertion a negative claim about
       # an external effect, with nothing pinning how the run ended. A command
       # that died before reaching the write leaves exactly that state. An

Taskfile.yml

@@ -40,6 +40,14 @@ tasks:
     cmds:
       - uv run pytest tests/e2e --docker {{.CLI_ARGS}}
 
+  # Each spec drives a clean headless Neovim against the config's own Lua and the
+  # plugins lazy installed, and exits non-zero on a failure. Every spec runs, so
+  # one run reports each that failed.
+  test:nvim:
+    desc: The nvim config's Lua specs, each in a headless Neovim
+    cmds:
+      - status=0; for spec in tests/nvim/*_spec.lua; do nvim --headless -u NONE -l "$spec" || status=1; done; exit $status
+
   test:watch:
     desc: Re-run the suite on file changes (requires entr)
     cmds:

configs/common/.config/nvim/init.lua

@@ -19,5 +19,7 @@ if not profiles.is_vscode then
   require('core.autocmds')
   -- Custom floating terminal (Space t t). VSCode has its own terminal.
   require('core.floaterminal')
+  -- The pull request beside a diff prs opened. Nothing where prs did not start nvim.
+  require('core.pull-request-panel').setup()
   require('lsp')
 end

configs/common/.config/nvim/lua/core/profiles.lua

@@ -1,5 +1,6 @@
--- Which plugins load, which is now only a question when Neovim is embedded in
--- VSCode through vscode-neovim. Everywhere else the whole set loads.
+-- Which kind of Neovim this is, and which plugins load in it. Two kinds load
+-- less than the whole set: one embedded in VSCode through vscode-neovim, and one
+-- prs started to show a pull request's diff.
 --
 -- An allowlist rather than a blocklist, because the spec list is not fully
 -- enumerable here: colorscheme-manager.lua synthesizes specs at startup by
@@ -29,13 +30,42 @@ local vscode_enabled = {
   ['typos'] = true,
 }
 
+-- prs starts nvim in a repo's checkout to show one pull request's diff, with
+-- PRS_DIFF_DOCUMENT naming the pull request's markdown document and
+-- PRS_DIFF_THREADS its review threads. Both are read once and cleared, so an
+-- nvim started from this one, such as lazygit's editor, is an ordinary nvim.
+local function taken(name)
+  local value = vim.env[name]
+  vim.env[name] = nil
+  if value == nil or value == '' then
+    return nil
+  end
+  return value
+end
+
+local document, threads = taken('PRS_DIFF_DOCUMENT'), taken('PRS_DIFF_THREADS')
+
+---@type { document: string, threads: string? }?
+M.pull_request_diff = document and { document = document, threads = threads } or nil
+
+-- Each keeps state for the directory nvim started in, which in a pull request's
+-- diff is the repo's own checkout.
+local pull_request_diff_disabled = {
+  -- Saving at exit would replace the repo's session with the diff's buffers,
+  -- which are gone once nvim exits.
+  ['auto-session'] = true,
+}
+
 --- Plugin condition function for lazy.nvim defaults.cond
 ---@param plugin LazyPlugin
 ---@return boolean
 function M.plugin_enabled(plugin)
   if M.is_vscode then
     return vscode_enabled[plugin.name] == true
   end
+  if M.pull_request_diff then
+    return not pull_request_diff_disabled[plugin.name]
+  end
   return true
 end