Set default formatter to nixfmt-rfc-style

oxalica · oxalica · commit 89e5a4e61ec0 · 2025-06-13T02:05:09.000-04:00
It's supposed to be the official formatting tool. See: <NixOS/rfcs#166>
diff --git a/crates/nil/src/handler.rs b/crates/nil/src/handler.rs
@@ -16,6 +16,11 @@ use std::process;
 use std::sync::Arc;
 use text_size::TextRange;
 
+const DEFAULT_FORMATTER: &str = match option_env!("CFG_DEFAULT_FORMATTER") {
+    Some(cmd) => cmd,
+    None => "nixfmt",
+};
+
 pub(crate) fn goto_definition(
     snap: StateSnapshot,
     params: GotoDefinitionParams,
@@ -219,19 +224,26 @@ pub(crate) fn formatting(
         Ok(stdout)
     }
 
-    let cmd =
-        snap.config.formatting_command.as_ref().context(
-            "No formatter configured. Set the nil.formatting.command LSP server setting.",
-        )?;
+    let cmd = match &snap.config.formatting_command {
+        Some(cmd) => cmd,
+        None => &vec![DEFAULT_FORMATTER.to_owned()],
+    };
 
     let (file_content, line_map) = {
         let vfs = snap.vfs();
         let (file, line_map) = convert::from_file(&vfs, &params.text_document)?;
         (vfs.content_for_file(file), line_map)
     };
 
-    let new_content = run_with_stdin(cmd, <Arc<[u8]>>::from(file_content.clone()))
-        .with_context(|| format!("Failed to run formatter {cmd:?}"))?;
+    let new_content =
+        run_with_stdin(cmd, <Arc<[u8]>>::from(file_content.clone())).with_context(|| {
+            let note = if snap.config.formatting_command.is_none() {
+                ", set `nil.formatting.command` in LSP setting to override the default"
+            } else {
+                ""
+            };
+            format!("Failed to run formatter {cmd:?}{note}")
+        })?;
 
     if new_content == *file_content {
         return Ok(None);
diff --git a/dev/nvim-lsp.nix b/dev/nvim-lsp.nix
@@ -89,9 +89,6 @@ let
       settings = {
         ['nil'] = {
           testSetting = 42,
-          formatting = {
-            command = { "nixfmt" },
-          },
         },
       },
     }
diff --git a/dev/vim-coc.nix b/dev/vim-coc.nix
@@ -99,7 +99,6 @@ let
     nil.server.path = pkgs.writeShellScript "nil" ''
       exec "$NIL_PATH" "$@"
     '';
-    nil.formatting.command = [ (pkgs.lib.getExe pkgs.nixfmt-rfc-style) ];
     nil.diagnostics.excludedFiles = [ "generated.nix" ];
     nil.nix.flake.autoEvalInputs = true;
     nil.nix.maxMemoryMB = 2048;
diff --git a/flake.nix b/flake.nix
@@ -23,7 +23,12 @@ rec {
       rev = self.rev or (lib.warn "Git changes are not committed" (self.dirtyRev or "dirty"));
 
       mkNil =
-        { rustPlatform, nixVersions, ... }:
+        {
+          rustPlatform,
+          nixVersions,
+          nixfmt-rfc-style,
+          ...
+        }:
         rustPlatform.buildRustPackage {
           pname = "nil";
           version = "unstable-${date}";
@@ -37,6 +42,7 @@ rec {
           nativeBuildInputs = [ (nixVersions.latest or nixVersions.unstable) ];
 
           CFG_RELEASE = "git-${rev}";
+          CFG_DEFAULT_FORMATTER = lib.getExe nixfmt-rfc-style;
 
           meta = {
             inherit description;
