From e17ecef2927f9a6a953f5689c17397f5cc31f972 Mon Sep 17 00:00:00 2001
From: XeroOl <xerool@protonmail.com>
Date: Tue, 8 Jul 2025 20:49:35 -0500
Subject: [PATCH] macroexpansion feature for hover and code action

---
 src/fennel-ls/formatter.fnl | 16 +++++++++++-----
 src/fennel-ls/handlers.fnl  | 26 ++++++++++++++++++++------
 test/hover.fnl              |  4 ++--
 3 files changed, 33 insertions(+), 13 deletions(-)

diff --git a/src/fennel-ls/formatter.fnl b/src/fennel-ls/formatter.fnl
index 399c10f..79469ac 100644
--- a/src/fennel-ls/formatter.fnl
+++ b/src/fennel-ls/formatter.fnl
@@ -166,14 +166,20 @@ fntype is one of fn or λ or lambda"
         "?")
       (view (or definition.binding definition.definition))))
 
-(λ hover-format [server name definition]
+(λ hover-format [server name definition ?opts]
   "Format code that will appear when the user hovers over a symbol"
   {:kind "markdown"
    :value (.. (code-block (get-stub server name definition))
-              (or (-?> (navigate.getmetadata server definition)
-                       (. :fnl/docstring)
-                       (->> (.. "\n---\n")))
-                  ""))})
+              (case (navigate.getmetadata server definition)
+                {: fnl/docstring}
+                (.. "\n---\n" fnl/docstring)
+                _ "")
+              (case (?. ?opts :macroexpansion)
+                macroexpansion
+                (.. "\n---\n"
+                    "Macro expands to:\n"
+                    (code-block macroexpansion))
+                _ ""))})
 
 ;; CompletionItemKind
 (local kinds
diff --git a/src/fennel-ls/handlers.fnl b/src/fennel-ls/handlers.fnl
index 13cab31..408f5e2 100644
--- a/src/fennel-ls/handlers.fnl
+++ b/src/fennel-ls/handlers.fnl
@@ -156,10 +156,16 @@ Every time the client sends a message, it gets handled by a function in the corr
   (let [file (files.get-by-uri server uri)
         byte (utils.position->byte file.text position server.position-encoding)]
     (case-try (analyzer.find-symbol file.ast byte)
-      symbol (analyzer.search server file symbol {} {: byte})
-      {:indeterminate nil &as result} {:contents (formatter.hover-format server (tostring symbol) result)
-                                       :range (message.ast->range server file
-                                                                  symbol)}
+      (symbol parents) (analyzer.search server file symbol {} {: byte})
+      {:indeterminate nil &as result}
+      (let [opts {:macroexpansion (case-try parents
+                                            (where [[(= symbol) &as parent]])
+                                            file.macro-calls
+                                            {parent expansion}
+                                            (fennel.view expansion)
+                                            (catch _ nil))}]
+        {:contents (formatter.hover-format server (tostring symbol) result opts)
+         :range (message.ast->range server file symbol)})
       (catch _ nil))))
 
 (set {:textDocument/completion requests.textDocument/completion
@@ -206,8 +212,16 @@ Every time the client sends a message, it gets handled by a function in the corr
        (pos<= range-2.start range-1.end)))
 
 (λ requests.textDocument/codeAction [server _send {: range :textDocument {: uri}}]
-  (let [file (files.get-by-uri server uri)]
-    (icollect [_ diagnostic (ipairs file.diagnostics)]
+  (let [file (files.get-by-uri server uri)
+        byte (utils.position->byte file.text range.start server.position-encoding)
+        results []]
+    (case-try (analyzer.find-symbol file.ast byte)
+      (symbol_ [[symbol_ &as parent]]) file.macro-calls
+      {parent expansion} (table.insert results
+                           {:title "Expand macro"
+                            :edit {:changes {uri [{:range (message.ast->range server file parent)
+                                                   :newText (fennel.view expansion)}]}}}))
+    (icollect [_ diagnostic (ipairs file.diagnostics) &into results]
       (if (overlap? diagnostic.range range)
         (message.diagnostic->code-action server file diagnostic :quickfix)))))
 
diff --git a/test/hover.fnl b/test/hover.fnl
index 45499da..62e896e 100644
--- a/test/hover.fnl
+++ b/test/hover.fnl
@@ -34,7 +34,7 @@
 
 (fn test-builtins []
   (check "(d|o nil)" "```fnl\n(do ...)\n```\n---\nEvaluate multiple forms; return last value.")
-  (check "(|doto nil (print))" "```fnl\n(doto val ...)\n```\n---\nEvaluate val and splice it into the first argument of subsequent forms.")
+  (check "(|doto nil (print))" "```fnl\n(doto val ...)\n```\n---\nEvaluate val and splice it into the first argument of subsequent forms.\n---\nMacro expands to:\n```fnl\n(do (print nil) nil)\n```")
   (check "(le|t [x 10] 10)" "```fnl\n(let [name1 val1 ... nameN valN] ...)\n```\n---\nIntroduces a new scope in which a given set of local bindings are used.")
   nil)
 
@@ -153,7 +153,7 @@ except that it sets a new message handler `msgh`.")
             \"docstring!\"
             `(,a ,b ,c))
           (fo|o print :hello :world)"
-         "```fnl\n(foo a b c)\n```\n---\ndocstring!")
+         "```fnl\n(foo a b c)\n```\n---\ndocstring!\n---\nMacro expands to:\n```fnl\n(print \"hello\" \"world\")\n```")
   ; (check {:main.fnl "(import-macros cool :cool)
   ;                    (coo|l.=)"
   ;         :cool.fnl ";; fennel-ls: macro-file