Add lsp signature help (#1755)

* Add lsp signature help

* Do not move signature help popup on multiple triggers

* Highlight current parameter in signature help

* Auto close signature help

* Position signature help above to not block completion

* Update signature help on backspace/insert mode delete

* Add lsp.auto-signature-help config option

* Add serde default annotation for LspConfig

* Show LSP inactive message only if signature help is invoked manually

* Do not assume valid signature help response from LSP

Malformed LSP responses are common, and these should not crash the
editor.

* Check signature help capability before sending request

* Reuse Open enum for PositionBias in popup

* Close signature popup and exit insert mode on escape

* Add config to control signature help docs display

* Use new Margin api in signature help

* Invoke signature help on changing to insert mode

1 files changed, 23 insertions, 19 deletions

diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index dad3db86..3ee75f6a 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -715,6 +715,8 @@ fn kill_to_line_start(cx: &mut Context) {
         Range::new(head, anchor)
     });
     delete_selection_insert_mode(doc, view, &selection);
+
+    lsp::signature_help_impl(cx, SignatureHelpInvoked::Automatic);
 }
 
 fn kill_to_line_end(cx: &mut Context) {
@@ -734,6 +736,8 @@ fn kill_to_line_end(cx: &mut Context) {
         new_range
     });
     delete_selection_insert_mode(doc, view, &selection);
+
+    lsp::signature_help_impl(cx, SignatureHelpInvoked::Automatic);
 }
 
 fn goto_first_nonwhitespace(cx: &mut Context) {
@@ -2399,7 +2403,8 @@ async fn make_format_callback(
     Ok(call)
 }
 
-enum Open {
+#[derive(PartialEq)]
+pub enum Open {
     Below,
     Above,
 }
@@ -2797,6 +2802,9 @@ pub mod insert {
         use helix_lsp::lsp;
         // if ch matches signature_help char, trigger
         let doc = doc_mut!(cx.editor);
+        // The language_server!() macro is not used here since it will
+        // print an "LSP not active for current buffer" message on
+        // every keypress.
         let language_server = match doc.language_server() {
             Some(language_server) => language_server,
             None => return,
@@ -2816,26 +2824,15 @@ pub mod insert {
         {
             // TODO: what if trigger is multiple chars long
             let is_trigger = triggers.iter().any(|trigger| trigger.contains(ch));
+            // lsp doesn't tell us when to close the signature help, so we request
+            // the help information again after common close triggers which should
+            // return None, which in turn closes the popup.
+            let close_triggers = &[')', ';', '.'];
 
-            if is_trigger {
-                super::signature_help(cx);
+            if is_trigger || close_triggers.contains(&ch) {
+                super::signature_help_impl(cx, SignatureHelpInvoked::Automatic);
             }
         }
-
-        // SignatureHelp {
-        // signatures: [
-        //  SignatureInformation {
-        //      label: "fn open(&mut self, path: PathBuf, action: Action) -> Result<DocumentId, Error>",
-        //      documentation: None,
-        //      parameters: Some(
-        //          [ParameterInformation { label: Simple("path: PathBuf"), documentation: None },
-        //          ParameterInformation { label: Simple("action: Action"), documentation: None }]
-        //      ),
-        //      active_parameter: Some(0)
-        //  }
-        // ],
-        // active_signature: None, active_parameter: Some(0)
-        // }
     }
 
     // The default insert hook: simply insert the character
@@ -2870,7 +2867,6 @@ pub mod insert {
         // this could also generically look at Transaction, but it's a bit annoying to look at
         // Operation instead of Change.
         for hook in &[language_server_completion, signature_help] {
-            // for hook in &[signature_help] {
             hook(cx, c);
         }
     }
@@ -3042,6 +3038,8 @@ pub mod insert {
                 }
             });
         doc.apply(&transaction, view.id);
+
+        lsp::signature_help_impl(cx, SignatureHelpInvoked::Automatic);
     }
 
     pub fn delete_char_forward(cx: &mut Context) {
@@ -3058,6 +3056,8 @@ pub mod insert {
                 )
             });
         doc.apply(&transaction, view.id);
+
+        lsp::signature_help_impl(cx, SignatureHelpInvoked::Automatic);
     }
 
     pub fn delete_word_backward(cx: &mut Context) {
@@ -3071,6 +3071,8 @@ pub mod insert {
             exclude_cursor(text, next, range)
         });
         delete_selection_insert_mode(doc, view, &selection);
+
+        lsp::signature_help_impl(cx, SignatureHelpInvoked::Automatic);
     }
 
     pub fn delete_word_forward(cx: &mut Context) {
@@ -3083,6 +3085,8 @@ pub mod insert {
             .clone()
             .transform(|range| movement::move_next_word_start(text, range, count));
         delete_selection_insert_mode(doc, view, &selection);
+
+        lsp::signature_help_impl(cx, SignatureHelpInvoked::Automatic);
     }
 }