5 files changed, 65 insertions, 21 deletions

diff --git a/crates/ra_ide/src/completion/completion_item.rs b/crates/ra_ide/src/completion/completion_item.rs
index 61867c0ff..19bbb2517 100644
--- a/crates/ra_ide/src/completion/completion_item.rs
+++ b/crates/ra_ide/src/completion/completion_item.rs
@@ -47,6 +47,10 @@ pub struct CompletionItem {
 
     /// Whether this item is marked as deprecated
     deprecated: bool,
+
+    /// If completing a function call, ask the editor to show parameter popup
+    /// after completion.
+    trigger_call_info: bool,
 }
 
 // We use custom debug for CompletionItem to make `insta`'s diffs more readable.
@@ -139,6 +143,7 @@ impl CompletionItem {
             kind: None,
             text_edit: None,
             deprecated: None,
+            trigger_call_info: None,
         }
     }
     /// What user sees in pop-up in the UI.
@@ -177,6 +182,10 @@ impl CompletionItem {
     pub fn deprecated(&self) -> bool {
         self.deprecated
     }
+
+    pub fn trigger_call_info(&self) -> bool {
+        self.trigger_call_info
+    }
 }
 
 /// A helper to make `CompletionItem`s.
@@ -193,6 +202,7 @@ pub(crate) struct Builder {
     kind: Option<CompletionItemKind>,
     text_edit: Option<TextEdit>,
     deprecated: Option<bool>,
+    trigger_call_info: Option<bool>,
 }
 
 impl Builder {
@@ -221,6 +231,7 @@ impl Builder {
             kind: self.kind,
             completion_kind: self.completion_kind,
             deprecated: self.deprecated.unwrap_or(false),
+            trigger_call_info: self.trigger_call_info.unwrap_or(false),
         }
     }
     pub(crate) fn lookup_by(mut self, lookup: impl Into<String>) -> Builder {
@@ -271,6 +282,10 @@ impl Builder {
         self.deprecated = Some(deprecated);
         self
     }
+    pub(crate) fn trigger_call_info(mut self) -> Builder {
+        self.trigger_call_info = Some(true);
+        self
+    }
 }
 
 impl<'a> Into<CompletionItem> for Builder {
diff --git a/crates/ra_ide/src/completion/presentation.rs b/crates/ra_ide/src/completion/presentation.rs
index dac232a85..aada4d025 100644
--- a/crates/ra_ide/src/completion/presentation.rs
+++ b/crates/ra_ide/src/completion/presentation.rs
@@ -103,7 +103,7 @@ impl Completions {
             }
         };
 
-        // If not an import, add parenthesis automatically.
+        // Add `<>` for generic types
         if ctx.is_path_type
             && !ctx.has_type_args
             && ctx.db.feature_flags.get("completion.insertion.add-call-parenthesis")
@@ -211,7 +211,7 @@ impl Completions {
                 .set_deprecated(is_deprecated(func, ctx.db))
                 .detail(function_signature.to_string());
 
-        // Add `<>` for generic types
+        // If not an import, add parenthesis automatically.
         if ctx.use_item_syntax.is_none()
             && !ctx.is_call
             && ctx.db.feature_flags.get("completion.insertion.add-call-parenthesis")
@@ -221,16 +221,26 @@ impl Completions {
             let (snippet, label) = if params.is_empty() || has_self_param && params.len() == 1 {
                 (format!("{}()$0", name), format!("{}()", name))
             } else {
-                let to_skip = if has_self_param { 1 } else { 0 };
-                let function_params_snippet =
-                    join(
+                builder = builder.trigger_call_info();
+                let snippet = if ctx
+                    .db
+                    .feature_flags
+                    .get("completion.insertion.add-argument-snippets")
+                {
+                    let to_skip = if has_self_param { 1 } else { 0 };
+                    let function_params_snippet = join(
                         function_signature.parameter_names.iter().skip(to_skip).enumerate().map(
                             |(index, param_name)| format!("${{{}:{}}}", index + 1, param_name),
                         ),
                     )
                     .separator(", ")
                     .to_string();
-                (format!("{}({})$0", name, function_params_snippet), format!("{}(…)", name))
+                    format!("{}({})$0", name, function_params_snippet)
+                } else {
+                    format!("{}($0)", name)
+                };
+
+                (snippet, format!("{}(…)", name))
             };
             builder = builder.lookup_by(name).label(label).insert_snippet(snippet);
         }
diff --git a/crates/ra_ide_db/src/feature_flags.rs b/crates/ra_ide_db/src/feature_flags.rs
index 76655f572..968415072 100644
--- a/crates/ra_ide_db/src/feature_flags.rs
+++ b/crates/ra_ide_db/src/feature_flags.rs
@@ -54,7 +54,9 @@ impl Default for FeatureFlags {
         FeatureFlags::new(&[
             ("lsp.diagnostics", true),
             ("completion.insertion.add-call-parenthesis", true),
+            ("completion.insertion.add-argument-snippets", true),
             ("completion.enable-postfix", true),
+            ("call-info.full", true),
             ("notifications.workspace-loaded", true),
             ("notifications.cargo-toml-not-found", true),
         ])
diff --git a/crates/rust-analyzer/src/conv.rs b/crates/rust-analyzer/src/conv.rs
index eeeb33e8f..a2d68c344 100644
--- a/crates/rust-analyzer/src/conv.rs
+++ b/crates/rust-analyzer/src/conv.rs
@@ -3,10 +3,10 @@
 
 use lsp_types::{
     self, CreateFile, DiagnosticSeverity, DocumentChangeOperation, DocumentChanges, Documentation,
-    Location, LocationLink, MarkupContent, MarkupKind, Position, Range, RenameFile, ResourceOp,
-    SemanticTokenModifier, SemanticTokenType, SymbolKind, TextDocumentEdit, TextDocumentIdentifier,
-    TextDocumentItem, TextDocumentPositionParams, Url, VersionedTextDocumentIdentifier,
-    WorkspaceEdit,
+    Location, LocationLink, MarkupContent, MarkupKind, ParameterInformation, ParameterLabel,
+    Position, Range, RenameFile, ResourceOp, SemanticTokenModifier, SemanticTokenType,
+    SignatureInformation, SymbolKind, TextDocumentEdit, TextDocumentIdentifier, TextDocumentItem,
+    TextDocumentPositionParams, Url, VersionedTextDocumentIdentifier, WorkspaceEdit,
 };
 use ra_ide::{
     translate_offset_with_edit, CompletionItem, CompletionItemKind, FileId, FilePosition,
@@ -150,6 +150,16 @@ impl ConvWith<(&LineIndex, LineEndings)> for CompletionItem {
             additional_text_edits: Some(additional_text_edits),
             documentation: self.documentation().map(|it| it.conv()),
             deprecated: Some(self.deprecated()),
+            command: if self.trigger_call_info() {
+                let cmd = lsp_types::Command {
+                    title: "triggerParameterHints".into(),
+                    command: "editor.action.triggerParameterHints".into(),
+                    arguments: None,
+                };
+                Some(cmd)
+            } else {
+                None
+            },
             ..Default::default()
         };
 
@@ -210,17 +220,20 @@ impl Conv for ra_ide::Documentation {
     }
 }
 
-impl Conv for ra_ide::FunctionSignature {
+impl ConvWith<bool> for ra_ide::FunctionSignature {
     type Output = lsp_types::SignatureInformation;
-    fn conv(self) -> Self::Output {
-        use lsp_types::{ParameterInformation, ParameterLabel, SignatureInformation};
-
-        let label = self.to_string();
-
-        let documentation = self.doc.map(|it| it.conv());
+    fn conv_with(self, concise: bool) -> Self::Output {
+        let (label, documentation, params) = if concise {
+            let mut params = self.parameters;
+            if self.has_self_param {
+                params.remove(0);
+            }
+            (params.join(", "), None, params)
+        } else {
+            (self.to_string(), self.doc.map(|it| it.conv()), self.parameters)
+        };
 
-        let parameters: Vec<ParameterInformation> = self
-            .parameters
+        let parameters: Vec<ParameterInformation> = params
             .into_iter()
             .map(|param| ParameterInformation {
                 label: ParameterLabel::Simple(param),
diff --git a/crates/rust-analyzer/src/main_loop/handlers.rs b/crates/rust-analyzer/src/main_loop/handlers.rs
index b5db1fd38..b498c90c9 100644
--- a/crates/rust-analyzer/src/main_loop/handlers.rs
+++ b/crates/rust-analyzer/src/main_loop/handlers.rs
@@ -459,8 +459,12 @@ pub fn handle_signature_help(
     let _p = profile("handle_signature_help");
     let position = params.try_conv_with(&world)?;
     if let Some(call_info) = world.analysis().call_info(position)? {
-        let active_parameter = call_info.active_parameter.map(|it| it as i64);
-        let sig_info = call_info.signature.conv();
+        let concise = !world.analysis().feature_flags().get("call-info.full");
+        let mut active_parameter = call_info.active_parameter.map(|it| it as i64);
+        if concise && call_info.signature.has_self_param {
+            active_parameter = active_parameter.map(|it| it.saturating_sub(1));
+        }
+        let sig_info = call_info.signature.conv_with(concise);
 
         Ok(Some(req::SignatureHelp {
             signatures: vec![sig_info],