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, 13 insertions, 1 deletions

diff --git a/helix-term/src/ui/editor.rs b/helix-term/src/ui/editor.rs
index 911ee0f0..849f0b0b 100644
--- a/helix-term/src/ui/editor.rs
+++ b/helix-term/src/ui/editor.rs
@@ -1,7 +1,7 @@
 use crate::{
     commands,
     compositor::{Component, Context, EventResult},
-    key,
+    job, key,
     keymap::{KeymapResult, Keymaps},
     ui::{Completion, ProgressSpinners},
 };
@@ -28,6 +28,7 @@ use std::borrow::Cow;
 use crossterm::event::{Event, MouseButton, MouseEvent, MouseEventKind};
 use tui::buffer::Buffer as Surface;
 
+use super::lsp::SignatureHelp;
 use super::statusline;
 
 pub struct EditorView {
@@ -1205,10 +1206,21 @@ impl Component for EditorView {
                             _ => unimplemented!(),
                         };
                         self.last_insert.1.clear();
+                        commands::signature_help_impl(
+                            &mut cx,
+                            commands::SignatureHelpInvoked::Automatic,
+                        );
                     }
                     (Mode::Insert, Mode::Normal) => {
                         // if exiting insert mode, remove completion
                         self.completion = None;
+                        // TODO: Use an on_mode_change hook to remove signature help
+                        context.jobs.callback(async {
+                            let call: job::Callback = Box::new(|_editor, compositor| {
+                                compositor.remove(SignatureHelp::ID);
+                            });
+                            Ok(call)
+                        });
                     }
                     _ => (),
                 }