8 files changed, 140 insertions, 31 deletions

diff --git a/crates/ra_batch/src/lib.rs b/crates/ra_batch/src/lib.rs
index 0db751465..f458ea300 100644
--- a/crates/ra_batch/src/lib.rs
+++ b/crates/ra_batch/src/lib.rs
@@ -3,7 +3,7 @@ use std::{collections::HashSet, error::Error, path::Path};
 use rustc_hash::FxHashMap;
 
 use ra_db::{CrateGraph, FileId, SourceRootId};
-use ra_ide_api::{AnalysisChange, AnalysisHost};
+use ra_ide_api::{AnalysisChange, AnalysisHost, FeatureFlags};
 use ra_project_model::{PackageRoot, ProjectWorkspace};
 use ra_vfs::{RootEntry, Vfs, VfsChange};
 use ra_vfs_glob::RustPackageFilterBuilder;
@@ -63,7 +63,7 @@ pub fn load(
     vfs: &mut Vfs,
 ) -> AnalysisHost {
     let lru_cap = std::env::var("RA_LRU_CAP").ok().and_then(|it| it.parse::<usize>().ok());
-    let mut host = AnalysisHost::new(lru_cap);
+    let mut host = AnalysisHost::new(lru_cap, FeatureFlags::default());
     let mut analysis_change = AnalysisChange::new();
     analysis_change.set_crate_graph(crate_graph);
 
diff --git a/crates/ra_ide_api/src/completion/presentation.rs b/crates/ra_ide_api/src/completion/presentation.rs
index 6878008d3..2b3f98482 100644
--- a/crates/ra_ide_api/src/completion/presentation.rs
+++ b/crates/ra_ide_api/src/completion/presentation.rs
@@ -118,7 +118,10 @@ impl Completions {
             .set_documentation(func.docs(ctx.db))
             .detail(detail);
         // If not an import, add parenthesis automatically.
-        if ctx.use_item_syntax.is_none() && !ctx.is_call {
+        if ctx.use_item_syntax.is_none()
+            && !ctx.is_call
+            && ctx.db.feature_flags.get("completion.insertion.add-call-parenthesis")
+        {
             tested_by!(inserts_parens_for_function_calls);
             let snippet =
                 if data.params().is_empty() || data.has_self_param() && data.params().len() == 1 {
diff --git a/crates/ra_ide_api/src/db.rs b/crates/ra_ide_api/src/db.rs
index fc8252e4b..f2e6b8f12 100644
--- a/crates/ra_ide_api/src/db.rs
+++ b/crates/ra_ide_api/src/db.rs
@@ -7,7 +7,7 @@ use ra_db::{
 
 use crate::{
     symbol_index::{self, SymbolsDatabase},
-    LineIndex,
+    FeatureFlags, LineIndex,
 };
 
 #[salsa::database(
@@ -22,6 +22,7 @@ use crate::{
 #[derive(Debug)]
 pub(crate) struct RootDatabase {
     runtime: salsa::Runtime<RootDatabase>,
+    pub(crate) feature_flags: Arc<FeatureFlags>,
     pub(crate) last_gc: time::Instant,
     pub(crate) last_gc_check: time::Instant,
 }
@@ -46,16 +47,17 @@ impl salsa::Database for RootDatabase {
 
 impl Default for RootDatabase {
     fn default() -> RootDatabase {
-        RootDatabase::new(None)
+        RootDatabase::new(None, FeatureFlags::default())
     }
 }
 
 impl RootDatabase {
-    pub fn new(lru_capacity: Option<usize>) -> RootDatabase {
+    pub fn new(lru_capacity: Option<usize>, feature_flags: FeatureFlags) -> RootDatabase {
         let mut db = RootDatabase {
             runtime: salsa::Runtime::default(),
             last_gc: time::Instant::now(),
             last_gc_check: time::Instant::now(),
+            feature_flags: Arc::new(feature_flags),
         };
         db.set_crate_graph_with_durability(Default::default(), Durability::HIGH);
         db.set_local_roots_with_durability(Default::default(), Durability::HIGH);
@@ -74,6 +76,7 @@ impl salsa::ParallelDatabase for RootDatabase {
             runtime: self.runtime.snapshot(self),
             last_gc: self.last_gc,
             last_gc_check: self.last_gc_check,
+            feature_flags: Arc::clone(&self.feature_flags),
         })
     }
 }
diff --git a/crates/ra_ide_api/src/feature_flags.rs b/crates/ra_ide_api/src/feature_flags.rs
new file mode 100644
index 000000000..9f82ac71c
--- /dev/null
+++ b/crates/ra_ide_api/src/feature_flags.rs
@@ -0,0 +1,67 @@
+use rustc_hash::FxHashMap;
+
+/// Feature flags hold fine-grained toggles for all *user-visible* features of
+/// rust-analyzer.
+///
+/// The exists such that users are able to disable any annoying feature (and,
+/// with many users and many features,  some features are bound to be annoying
+/// for some users)
+///
+/// Note that we purposefully use run-time checked strings, and not something
+/// checked at compile time, to keep things simple and flexible.
+///
+/// Also note that, at the moment, `FeatureFlags` also store features for
+/// `ra_lsp_server`. This should be benign layering violation.
+#[derive(Debug)]
+pub struct FeatureFlags {
+    flags: FxHashMap<String, bool>,
+}
+
+impl FeatureFlags {
+    fn new(flags: &[(&str, bool)]) -> FeatureFlags {
+        let flags = flags
+            .iter()
+            .map(|&(name, value)| {
+                check_flag_name(name);
+                (name.to_string(), value)
+            })
+            .collect();
+        FeatureFlags { flags }
+    }
+
+    pub fn set(&mut self, flag: &str, value: bool) -> Result<(), ()> {
+        match self.flags.get_mut(flag) {
+            None => Err(()),
+            Some(slot) => {
+                *slot = value;
+                Ok(())
+            }
+        }
+    }
+
+    pub fn get(&self, flag: &str) -> bool {
+        match self.flags.get(flag) {
+            None => panic!("unknown flag: {:?}", flag),
+            Some(value) => *value,
+        }
+    }
+}
+
+impl Default for FeatureFlags {
+    fn default() -> FeatureFlags {
+        FeatureFlags::new(&[
+            ("lsp.diagnostics", true),
+            ("completion.insertion.add-call-parenthesis", true),
+            ("notifications.workspace-loaded", true),
+        ])
+    }
+}
+
+fn check_flag_name(flag: &str) {
+    for c in flag.bytes() {
+        match c {
+            b'a'..=b'z' | b'-' | b'.' => (),
+            _ => panic!("flag name does not match conventions: {:?}", flag),
+        }
+    }
+}
diff --git a/crates/ra_ide_api/src/lib.rs b/crates/ra_ide_api/src/lib.rs
index fa4ae4379..514dcaf96 100644
--- a/crates/ra_ide_api/src/lib.rs
+++ b/crates/ra_ide_api/src/lib.rs
@@ -14,6 +14,7 @@ mod db;
 pub mod mock_analysis;
 mod symbol_index;
 mod change;
+mod feature_flags;
 
 mod status;
 mod completion;
@@ -63,6 +64,7 @@ pub use crate::{
     completion::{CompletionItem, CompletionItemKind, InsertTextFormat},
     diagnostics::Severity,
     display::{file_structure, FunctionSignature, NavigationTarget, StructureNode},
+    feature_flags::FeatureFlags,
     folding_ranges::{Fold, FoldKind},
     hover::HoverResult,
     inlay_hints::{InlayHint, InlayKind},
@@ -247,13 +249,13 @@ pub struct AnalysisHost {
 
 impl Default for AnalysisHost {
     fn default() -> AnalysisHost {
-        AnalysisHost::new(None)
+        AnalysisHost::new(None, FeatureFlags::default())
     }
 }
 
 impl AnalysisHost {
-    pub fn new(lru_capcity: Option<usize>) -> AnalysisHost {
-        AnalysisHost { db: db::RootDatabase::new(lru_capcity) }
+    pub fn new(lru_capcity: Option<usize>, feature_flags: FeatureFlags) -> AnalysisHost {
+        AnalysisHost { db: db::RootDatabase::new(lru_capcity, feature_flags) }
     }
     /// Returns a snapshot of the current state, which you can query for
     /// semantic information.
@@ -261,6 +263,10 @@ impl AnalysisHost {
         Analysis { db: self.db.snapshot() }
     }
 
+    pub fn feature_flags(&self) -> &FeatureFlags {
+        &self.db.feature_flags
+    }
+
     /// Applies changes to the current state of the world. If there are
     /// outstanding snapshots, they will be canceled.
     pub fn apply_change(&mut self, change: AnalysisChange) {
@@ -319,6 +325,10 @@ impl Analysis {
         (host.analysis(), file_id)
     }
 
+    pub fn feature_flags(&self) -> &FeatureFlags {
+        &self.db.feature_flags
+    }
+
     /// Debug info about the current state of the analysis
     pub fn status(&self) -> Cancelable<String> {
         self.with_db(|db| status::status(&*db))
diff --git a/crates/ra_lsp_server/src/config.rs b/crates/ra_lsp_server/src/config.rs
index 71838b89c..5c5ae3e18 100644
--- a/crates/ra_lsp_server/src/config.rs
+++ b/crates/ra_lsp_server/src/config.rs
@@ -1,3 +1,5 @@
+use rustc_hash::FxHashMap;
+
 use serde::{Deserialize, Deserializer};
 
 /// Client provided initialization options
@@ -12,12 +14,6 @@ pub struct ServerConfig {
     #[serde(deserialize_with = "nullable_bool_false")]
     pub publish_decorations: bool,
 
-    /// Whether or not the workspace loaded notification should be sent
-    ///
-    /// Defaults to `true`
-    #[serde(deserialize_with = "nullable_bool_true")]
-    pub show_workspace_loaded: bool,
-
     pub exclude_globs: Vec<String>,
 
     pub lru_capacity: Option<usize>,
@@ -25,16 +21,19 @@ pub struct ServerConfig {
     /// For internal usage to make integrated tests faster.
     #[serde(deserialize_with = "nullable_bool_true")]
     pub with_sysroot: bool,
+
+    /// Fine grained feature flags to disable specific features.
+    pub feature_flags: FxHashMap<String, bool>,
 }
 
 impl Default for ServerConfig {
     fn default() -> ServerConfig {
         ServerConfig {
             publish_decorations: false,
-            show_workspace_loaded: true,
             exclude_globs: Vec::new(),
             lru_capacity: None,
             with_sysroot: true,
+            feature_flags: FxHashMap::default(),
         }
     }
 }
diff --git a/crates/ra_lsp_server/src/main_loop.rs b/crates/ra_lsp_server/src/main_loop.rs
index c0395c6d8..ce25ff162 100644
--- a/crates/ra_lsp_server/src/main_loop.rs
+++ b/crates/ra_lsp_server/src/main_loop.rs
@@ -9,7 +9,7 @@ use gen_lsp_server::{
     handle_shutdown, ErrorCode, RawMessage, RawNotification, RawRequest, RawResponse,
 };
 use lsp_types::{ClientCapabilities, NumberOrString};
-use ra_ide_api::{Canceled, FileId, LibraryData};
+use ra_ide_api::{Canceled, FeatureFlags, FileId, LibraryData};
 use ra_prof::profile;
 use ra_vfs::VfsTask;
 use serde::{de::DeserializeOwned, Serialize};
@@ -56,7 +56,7 @@ pub fn main_loop(
     msg_receiver: &Receiver<RawMessage>,
     msg_sender: &Sender<RawMessage>,
 ) -> Result<()> {
-    log::debug!("server_config: {:?}", config);
+    log::info!("server_config: {:#?}", config);
     // FIXME: support dynamic workspace loading.
     let workspaces = {
         let ws_worker = workspace_loader(config.with_sysroot);
@@ -83,6 +83,21 @@ pub fn main_loop(
         .iter()
         .map(|glob| ra_vfs_glob::Glob::new(glob))
         .collect::<std::result::Result<Vec<_>, _>>()?;
+    let feature_flags = {
+        let mut ff = FeatureFlags::default();
+        for (flag, value) in config.feature_flags {
+            if let Err(_) = ff.set(flag.as_str(), value) {
+                log::error!("unknown feature flag: {:?}", flag);
+                show_message(
+                    req::MessageType::Error,
+                    format!("unknown feature flag: {:?}", flag),
+                    msg_sender,
+                );
+            }
+        }
+        ff
+    };
+    log::info!("feature_flags: {:#?}", feature_flags);
     let mut state = WorldState::new(
         ws_roots,
         workspaces,
@@ -90,13 +105,13 @@ pub fn main_loop(
         &globs,
         Options {
             publish_decorations: config.publish_decorations,
-            show_workspace_loaded: config.show_workspace_loaded,
             supports_location_link: client_caps
                 .text_document
                 .and_then(|it| it.definition)
                 .and_then(|it| it.link_support)
                 .unwrap_or(false),
         },
+        feature_flags,
     );
 
     let pool = ThreadPool::new(THREADPOOL_SIZE);
@@ -276,7 +291,7 @@ fn main_loop_inner(
             && in_flight_libraries == 0
         {
             let n_packages: usize = state.workspaces.iter().map(|it| it.n_packages()).sum();
-            if state.options.show_workspace_loaded {
+            if state.feature_flags().get("notifications.workspace-loaded") {
                 let msg = format!("workspace loaded, {} rust packages", n_packages);
                 show_message(req::MessageType::Info, msg, msg_sender);
             }
@@ -587,17 +602,20 @@ fn update_file_notifications_on_threadpool(
     subscriptions: Vec<FileId>,
 ) {
     log::trace!("updating notifications for {:?}", subscriptions);
+    let publish_diagnostics = world.feature_flags().get("lsp.diagnostics");
     pool.execute(move || {
         for file_id in subscriptions {
-            match handlers::publish_diagnostics(&world, file_id) {
-                Err(e) => {
-                    if !is_canceled(&e) {
-                        log::error!("failed to compute diagnostics: {:?}", e);
+            if publish_diagnostics {
+                match handlers::publish_diagnostics(&world, file_id) {
+                    Err(e) => {
+                        if !is_canceled(&e) {
+                            log::error!("failed to compute diagnostics: {:?}", e);
+                        }
+                    }
+                    Ok(params) => {
+                        let not = RawNotification::new::<req::PublishDiagnostics>(&params);
+                        sender.send(Task::Notify(not)).unwrap();
                     }
-                }
-                Ok(params) => {
-                    let not = RawNotification::new::<req::PublishDiagnostics>(&params);
-                    sender.send(Task::Notify(not)).unwrap();
                 }
             }
             if publish_decorations {
diff --git a/crates/ra_lsp_server/src/world.rs b/crates/ra_lsp_server/src/world.rs
index 10f96812f..6696dff71 100644
--- a/crates/ra_lsp_server/src/world.rs
+++ b/crates/ra_lsp_server/src/world.rs
@@ -7,7 +7,8 @@ use gen_lsp_server::ErrorCode;
 use lsp_types::Url;
 use parking_lot::RwLock;
 use ra_ide_api::{
-    Analysis, AnalysisChange, AnalysisHost, CrateGraph, FileId, LibraryData, SourceRootId,
+    Analysis, AnalysisChange, AnalysisHost, CrateGraph, FeatureFlags, FileId, LibraryData,
+    SourceRootId,
 };
 use ra_vfs::{LineEndings, RootEntry, Vfs, VfsChange, VfsFile, VfsRoot};
 use ra_vfs_glob::{Glob, RustPackageFilterBuilder};
@@ -22,7 +23,6 @@ use crate::{
 #[derive(Debug, Clone)]
 pub struct Options {
     pub publish_decorations: bool,
-    pub show_workspace_loaded: bool,
     pub supports_location_link: bool,
 }
 
@@ -58,6 +58,7 @@ impl WorldState {
         lru_capacity: Option<usize>,
         exclude_globs: &[Glob],
         options: Options,
+        feature_flags: FeatureFlags,
     ) -> WorldState {
         let mut change = AnalysisChange::new();
 
@@ -99,7 +100,7 @@ impl WorldState {
         }
         change.set_crate_graph(crate_graph);
 
-        let mut analysis_host = AnalysisHost::new(lru_capacity);
+        let mut analysis_host = AnalysisHost::new(lru_capacity, feature_flags);
         analysis_host.apply_change(change);
         WorldState {
             options,
@@ -184,6 +185,10 @@ impl WorldState {
     pub fn complete_request(&mut self, request: CompletedRequest) {
         self.latest_requests.write().record(request)
     }
+
+    pub fn feature_flags(&self) -> &FeatureFlags {
+        self.analysis_host.feature_flags()
+    }
 }
 
 impl WorldSnapshot {
@@ -246,4 +251,8 @@ impl WorldSnapshot {
         let path = self.vfs.read().file2path(VfsFile(file_id.0));
         self.workspaces.iter().find_map(|ws| ws.workspace_root_for(&path))
     }
+
+    pub fn feature_flags(&self) -> &FeatureFlags {
+        self.analysis.feature_flags()
+    }
 }