Eglot: escape literal % characters in URIs

Escape literal % characters in Eglot URIs

Otherwise, a literal % in a file-name will be interpreted (by the
language server) as if it were a part of a percent-encoded sequence.

See Bug#78984 for context on why `url-path-allowed-chars' cannot be
changed to escape literal % characters.

* lisp/progmodes/eglot.el (eglot--uri-path-allowed-chars): Escape %,
remove the redundant variable definition.
* test/lisp/progmodes/eglot-tests.el (eglot-test-path-to-uri-escape):
test it.

lisp/progmodes/eglot.el

@@ -675,6 +675,7 @@ This can be useful when using docker to run a language server.")
 (defconst eglot--uri-path-allowed-chars
   (let ((vec (copy-sequence url-path-allowed-chars)))
     (aset vec ?: nil) ;; see github#639
+    (aset vec ?% nil) ;; see bug#78984
     vec)
   "Like `url-path-allowed-chars' but more restrictive.")
 
@@ -2008,12 +2009,6 @@ If optional MARKER, return a marker instead"
 
 
 ;;; More helpers
-(defconst eglot--uri-path-allowed-chars
-  (let ((vec (copy-sequence url-path-allowed-chars)))
-    (aset vec ?: nil) ;; see github#639
-    vec)
-  "Like `url-path-allowed-chars' but more restrictive.")
-
 (defun eglot--snippet-expansion-fn ()
   "Compute a function to expand snippets.
 Doubles as an indicator of snippet support."

test/lisp/progmodes/eglot-tests.el

@@ -1469,6 +1469,10 @@ GUESSED-MAJOR-MODES-SYM are bound to the useful return values of
   (should (string-suffix-p "c%3A/Users/Foo/bar.lisp"
                            (eglot-path-to-uri "c:/Users/Foo/bar.lisp"))))
 
+(ert-deftest eglot-test-path-to-uri-escape ()
+  (should (equal "file:///path/with%20%25%20funny%20%3F%20characters"
+                 (eglot-path-to-uri "/path/with % funny ? characters"))))
+
 (ert-deftest eglot-test-same-server-multi-mode ()
   "Check single LSP instance manages multiple modes in same project."
   (skip-unless (executable-find "clangd"))