4 files changed, 94 insertions, 60 deletions

diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index 628ed107e..fb7895ce0 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -9,9 +9,77 @@
 
 use rustc_hash::FxHashMap;
 
+use lsp_types::TextDocumentClientCapabilities;
+use ra_flycheck::FlycheckConfig;
+use ra_ide::InlayHintsConfig;
 use ra_project_model::CargoFeatures;
 use serde::{Deserialize, Deserializer};
 
+#[derive(Debug, Clone)]
+pub struct Config {
+    pub publish_decorations: bool,
+    pub supports_location_link: bool,
+    pub line_folding_only: bool,
+    pub inlay_hints: InlayHintsConfig,
+    pub rustfmt: RustfmtConfig,
+    pub check: Option<FlycheckConfig>,
+    pub vscode_lldb: bool,
+    pub proc_macro_srv: Option<String>,
+}
+
+#[derive(Debug, Clone)]
+pub enum RustfmtConfig {
+    Rustfmt {
+        extra_args: Vec<String>,
+    },
+    #[allow(unused)]
+    CustomCommand {
+        command: String,
+        args: Vec<String>,
+    },
+}
+
+impl Default for RustfmtConfig {
+    fn default() -> Self {
+        RustfmtConfig::Rustfmt { extra_args: Vec::new() }
+    }
+}
+
+pub(crate) fn get_config(
+    config: &ServerConfig,
+    text_document_caps: Option<&TextDocumentClientCapabilities>,
+) -> Config {
+    Config {
+        publish_decorations: config.publish_decorations,
+        supports_location_link: text_document_caps
+            .and_then(|it| it.definition)
+            .and_then(|it| it.link_support)
+            .unwrap_or(false),
+        line_folding_only: text_document_caps
+            .and_then(|it| it.folding_range.as_ref())
+            .and_then(|it| it.line_folding_only)
+            .unwrap_or(false),
+        inlay_hints: InlayHintsConfig {
+            type_hints: config.inlay_hints_type,
+            parameter_hints: config.inlay_hints_parameter,
+            chaining_hints: config.inlay_hints_chaining,
+            max_length: config.inlay_hints_max_length,
+        },
+        check: if config.cargo_watch_enable {
+            Some(FlycheckConfig::CargoCommand {
+                command: config.cargo_watch_command.clone(),
+                all_targets: config.cargo_watch_all_targets,
+                extra_args: config.cargo_watch_args.clone(),
+            })
+        } else {
+            None
+        },
+        rustfmt: RustfmtConfig::Rustfmt { extra_args: config.rustfmt_args.clone() },
+        vscode_lldb: config.vscode_lldb,
+        proc_macro_srv: None, // FIXME: get this from config
+    }
+}
+
 /// Client provided initialization options
 #[derive(Deserialize, Clone, Debug, PartialEq, Eq)]
 #[serde(rename_all = "camelCase", default)]
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index a89ea86ea..de40e2ac2 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -21,8 +21,8 @@ use lsp_types::{
     WorkDoneProgressBegin, WorkDoneProgressCreateParams, WorkDoneProgressEnd,
     WorkDoneProgressReport,
 };
-use ra_flycheck::{url_from_path_with_drive_lowercasing, CheckTask, FlycheckConfig};
-use ra_ide::{Canceled, FileId, InlayHintsConfig, LibraryData, SourceRootId};
+use ra_flycheck::{url_from_path_with_drive_lowercasing, CheckTask};
+use ra_ide::{Canceled, FileId, LibraryData, SourceRootId};
 use ra_prof::profile;
 use ra_vfs::{VfsFile, VfsTask, Watch};
 use relative_path::RelativePathBuf;
@@ -31,6 +31,7 @@ use serde::{de::DeserializeOwned, Serialize};
 use threadpool::ThreadPool;
 
 use crate::{
+    config::get_config,
     diagnostics::DiagnosticTask,
     feature_flags::FeatureFlags,
     main_loop::{
@@ -38,7 +39,7 @@ use crate::{
         subscriptions::Subscriptions,
     },
     req,
-    world::{Config, WorldSnapshot, WorldState},
+    world::{WorldSnapshot, WorldState},
     Result, ServerConfig,
 };
 use req::ConfigurationParams;
@@ -81,41 +82,6 @@ fn get_feature_flags(config: &ServerConfig, connection: &Connection) -> FeatureF
     ff
 }
 
-fn get_config(
-    config: &ServerConfig,
-    text_document_caps: Option<&TextDocumentClientCapabilities>,
-) -> Config {
-    Config {
-        publish_decorations: config.publish_decorations,
-        supports_location_link: text_document_caps
-            .and_then(|it| it.definition)
-            .and_then(|it| it.link_support)
-            .unwrap_or(false),
-        line_folding_only: text_document_caps
-            .and_then(|it| it.folding_range.as_ref())
-            .and_then(|it| it.line_folding_only)
-            .unwrap_or(false),
-        inlay_hints: InlayHintsConfig {
-            type_hints: config.inlay_hints_type,
-            parameter_hints: config.inlay_hints_parameter,
-            chaining_hints: config.inlay_hints_chaining,
-            max_length: config.inlay_hints_max_length,
-        },
-        check: if config.cargo_watch_enable {
-            Some(FlycheckConfig::CargoCommand {
-                command: config.cargo_watch_command.clone(),
-                all_targets: config.cargo_watch_all_targets,
-                extra_args: config.cargo_watch_args.clone(),
-            })
-        } else {
-            None
-        },
-        rustfmt_args: config.rustfmt_args.clone(),
-        vscode_lldb: config.vscode_lldb,
-        proc_macro_srv: None, // FIXME: get this from config
-    }
-}
-
 pub fn main_loop(
     ws_roots: Vec<PathBuf>,
     client_caps: ClientCapabilities,
diff --git a/crates/rust-analyzer/src/main_loop/handlers.rs b/crates/rust-analyzer/src/main_loop/handlers.rs
index d5cb5d137..bb99b38a8 100644
--- a/crates/rust-analyzer/src/main_loop/handlers.rs
+++ b/crates/rust-analyzer/src/main_loop/handlers.rs
@@ -31,6 +31,7 @@ use stdx::format_to;
 
 use crate::{
     cargo_target_spec::CargoTargetSpec,
+    config::RustfmtConfig,
     conv::{
         to_call_hierarchy_item, to_location, Conv, ConvWith, FoldConvCtx, MapConvWith, TryConvWith,
         TryConvWithToVec,
@@ -610,13 +611,24 @@ pub fn handle_formatting(
     let file_line_index = world.analysis().file_line_index(file_id)?;
     let end_position = TextUnit::of_str(&file).conv_with(&file_line_index);
 
-    let mut rustfmt = process::Command::new("rustfmt");
-    rustfmt.args(&world.config.rustfmt_args);
-    if let Some(&crate_id) = crate_ids.first() {
-        // Assume all crates are in the same edition
-        let edition = world.analysis().crate_edition(crate_id)?;
-        rustfmt.args(&["--edition", &edition.to_string()]);
-    }
+    let mut rustfmt = match &world.config.rustfmt {
+        RustfmtConfig::Rustfmt { extra_args } => {
+            let mut cmd = process::Command::new("rustfmt");
+            cmd.args(extra_args);
+            if let Some(&crate_id) = crate_ids.first() {
+                // Assume all crates are in the same edition
+                let edition = world.analysis().crate_edition(crate_id)?;
+                cmd.arg("--edition");
+                cmd.arg(edition.to_string());
+            }
+            cmd
+        }
+        RustfmtConfig::CustomCommand { command, args } => {
+            let mut cmd = process::Command::new(command);
+            cmd.args(args);
+            cmd
+        }
+    };
 
     if let Ok(path) = params.text_document.uri.to_file_path() {
         if let Some(parent) = path.parent() {
diff --git a/crates/rust-analyzer/src/world.rs b/crates/rust-analyzer/src/world.rs
index 2db058eb1..124de4d8e 100644
--- a/crates/rust-analyzer/src/world.rs
+++ b/crates/rust-analyzer/src/world.rs
@@ -11,10 +11,9 @@ use std::{
 use crossbeam_channel::{unbounded, Receiver};
 use lsp_types::Url;
 use parking_lot::RwLock;
-use ra_flycheck::{url_from_path_with_drive_lowercasing, Flycheck, FlycheckConfig};
+use ra_flycheck::{url_from_path_with_drive_lowercasing, Flycheck};
 use ra_ide::{
-    Analysis, AnalysisChange, AnalysisHost, CrateGraph, FileId, InlayHintsConfig, LibraryData,
-    SourceRootId,
+    Analysis, AnalysisChange, AnalysisHost, CrateGraph, FileId, LibraryData, SourceRootId,
 };
 use ra_project_model::{get_rustc_cfg_options, ProcMacroClient, ProjectWorkspace};
 use ra_vfs::{LineEndings, RootEntry, Vfs, VfsChange, VfsFile, VfsRoot, VfsTask, Watch};
@@ -22,6 +21,7 @@ use relative_path::RelativePathBuf;
 use stdx::format_to;
 
 use crate::{
+    config::Config,
     diagnostics::{CheckFixes, DiagnosticCollection},
     feature_flags::FeatureFlags,
     main_loop::pending_requests::{CompletedRequest, LatestRequests},
@@ -51,18 +51,6 @@ fn create_flycheck(workspaces: &[ProjectWorkspace], config: &Config) -> Option<F
         })
 }
 
-#[derive(Debug, Clone)]
-pub struct Config {
-    pub publish_decorations: bool,
-    pub supports_location_link: bool,
-    pub line_folding_only: bool,
-    pub inlay_hints: InlayHintsConfig,
-    pub rustfmt_args: Vec<String>,
-    pub check: Option<FlycheckConfig>,
-    pub vscode_lldb: bool,
-    pub proc_macro_srv: Option<String>,
-}
-
 /// `WorldState` is the primary mutable state of the language server
 ///
 /// The most interesting components are `vfs`, which stores a consistent