Trigger parameter info automatically

See microsoft/vscode#64023

Author: matklad

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 {

crates/ra_ide/src/completion/presentation.rs

@@ -221,6 +221,7 @@ impl Completions {
             let (snippet, label) = if params.is_empty() || has_self_param && params.len() == 1 {
                 (format!("{}()$0", name), format!("{}()", name))
             } else {
+                builder = builder.trigger_call_info();
                 let snippet = if ctx
                     .db
                     .feature_flags

crates/rust-analyzer/src/conv.rs

@@ -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()
         };