language-server: add function signature on hover

Add function signature on hover. Fixes bug around autocomplete
not working properly when the cursor was mid-word.

pkg/arvo/app/language-server.hoon

@@ -23,6 +23,7 @@
       $%  [%sync changes=(list change)]
           [%completion position]
           [%commit @ud]
+          [%hover position]
       ==
   ==
 ::
@@ -74,6 +75,7 @@
     :~  sync+sync
         completion+position
         commit+ni
+        hover+position
     ==
     ~
   ==
@@ -132,6 +134,7 @@
       %sync        (handle-sync buf +>.lsp-req)
       %completion  (handle-completion buf +>.lsp-req)
       %commit      (handle-commit buf uri.lsp-req)
+      %hover       (handle-hover buf +>.lsp-req)
     ==
   =.  bufs
     (~(put by bufs) uri.lsp-req buf)
@@ -183,6 +186,30 @@
     |
   ==
 ::
+++  handle-hover
+  |=  [buf=wall row=@ud col=@ud]
+  ^-  [(list move) wall]
+  =/  txt
+    (zing (join "\0a" buf))
+  =+  (get-id:auto (get-pos buf row col) txt)
+  ?~  id
+    [(json-response *json) buf]
+  =/  match/(unit [=term =type])
+    (search-exact:auto u.id (get-identifiers:auto -:!>(..zuse)))
+  ?~  match
+    [(json-response *json) buf]
+  =/  contents
+    %-  crip
+    ;:  weld
+      "`"
+      ~(ram re ~(duck easy-print type.u.match))
+      "`"
+    ==
+  :_  buf
+  %-  json-response
+  %-  pairs:enjs:format
+  [contents+s+contents ~]
+::
 ++  handle-sync
   |=  [buf=wall changes=(list change)]
   :-  (json-response *json)
@@ -254,16 +281,7 @@
   =,  enjs:format
   %-  json-response
   ?:  ?=(%| -.tl)
-    %-  pairs
-    :~  good+b+|
-        :+  %diagnostics  %a  :_  ~
-        =/  loc  (pairs line+(numb (dec row.p.tl)) character+(numb col.p.tl) ~)
-        %-  pairs
-        :~  range+(pairs start+loc end+loc ~)
-            severity+n+'1'
-            message+s+'syntax error'
-        ==
-    ==
+    (format-diagnostic p.tl)
   ?~  p.tl
     *json
   %-  pairs

pkg/arvo/lib/language-server/complete.hoon

@@ -68,6 +68,17 @@
       [%hold *]  $(ty ~(repo ut ty))
   ==
 ::
+++  search-exact
+  |=  [sid=term ids=(list [term type])]
+  ^-  (unit [term type])
+  =/  match/(list [term type])
+    %+  skim  ids
+    |=  [id=term ty=type]
+    =(sid id)
+  ?~  match
+    ~
+  [~ i.match]
+::
 ::  Get all the identifiers that start with sid.
 ::
 ++  search-prefix
@@ -234,18 +245,14 @@
   ^-  (unit [term type])
   ~
 ::
-::  Insert magic marker in hoon source at the given position.
-::
-++  insert-magic
+++  get-id
   |=  [pos=@ud txt=tape]
-  ^-  [back-pos=@ud fore-pos=@ud txt=tape]
-  ::  Find beg-pos by searching backward to where the current term
-  ::  begins
-  ::
+  ^-  [forward=(unit term) backward=(unit term) id=(unit term)]
   =/  forward=(unit term)
     %+  scan  `tape`(slag pos txt)
     ;~(sfix (punt sym) (star ;~(pose prn (just `@`10))))
   =/  backward=(unit term)
+    %-  (lift |=(t=@tas (crip (flop (trip t)))))
     %+  scan  `tape`(flop (scag pos txt))
     ;~(sfix (punt sym) (star ;~(pose prn (just `@`10))))
   =/  id=(unit term)
@@ -256,6 +263,16 @@
     ?~  backward
       `u.forward
     `(cat 3 u.backward u.forward)
+  [forward backward id]
+::
+::  Insert magic marker in hoon source at the given position.
+::
+++  insert-magic
+  |=  [pos=@ud txt=tape]
+  ^-  [back-pos=@ud fore-pos=@ud txt=tape]
+  ::  Find beg-pos by searching backward to where the current term
+  ::  begins
+  =+  (get-id pos txt)
   =/  back-pos
     ?~  backward
       pos