Allow custom filter functions for jsonian-find (#56)

Allow custom filter functions

README.md

@@ -104,7 +104,7 @@ function `jsonian-enable-flycheck` which adds `jsonian-mode` to all checkers tha
 
 ### Functions
 
-#### jsonian-path (&optional POS BUFFER)
+#### jsonian-path
 
 Return the JSON path (as a list) of POINT in BUFFER.
 It is assumed that BUFFER is entirely JSON and that the json is
@@ -134,6 +134,18 @@ b. leveraging C code whenever possible.
 
 By default, this command is bound to `C-c C-p`.
 
+##### Customization
+
+`jsonian-find` needs to filter it's results. By default, it filters by prefix. You can
+customize the prefix function by setting
+`jsonian-find-filter-fn`. [Orderless](https://github.com/oantolin/orderless) provides an
+excellent fuzzy search implementation, which you can use via:
+
+``` emacs-lisp
+(with-eval-after-load 'orderless
+    (setq jsonian-find-filter-fn #'orderless-filter))
+```
+
 #### jsonian-edit-string
 
 Edit the string at point in another buffer. The string is expanded when being edited and
@@ -158,7 +170,7 @@ buffer. When the element is selected, jump to that point in the buffer.
 
 By default, this command is bound to `C-c C-f`.
 
-### jsonian-format-region
+#### jsonian-format-region
 
 Maximize the JSON contents of the region. This is equivalent to the built-in function
 `json-pretty-print`, but much faster (see "\#\# Benchmarks"). For example:

jsonian.el

@@ -71,6 +71,11 @@ nil means that `jsonian-mode' will infer the correct indentation."
   :type 'integer
   :group 'jsonian)
 
+(defcustom jsonian-find-filter-fn #'jsonian--filter-prefix
+  "The function used to filter `jsonian-find' results."
+  :type 'func
+  :group 'jsonian)
+
 (defgroup jsonian-c nil
   "A major mode for editing JSON with comments."
   :prefix "jsonian-c-" :group 'jsonian)
@@ -1372,14 +1377,18 @@ CACHE is the value of `jsonian--cache' for the buffer being completed against."
                  (or (and node (jsonian--cached-node-preview node)) ""))))
             paths)))
 
+(defun jsonian--filter-prefix (prefix paths)
+  "Filter out entries in PATHS that do not start with PREFIX."
+  (seq-filter (apply-partially #'string-prefix-p prefix) paths))
+
 (defun jsonian--completing-sort (prefix paths)
   "The completing sort function for `jsonian--find-completion'.
 PREFIX is the string to compare against.
 PATHS is the list of returned paths."
   (if-let* ((segment (car-safe (last (jsonian--parse-path prefix))))
             (prefix (jsonian--display-segment-end segment)))
       (sort
-       (seq-filter (apply-partially #'string-prefix-p prefix) paths)
+       (funcall jsonian-find-filter-fn prefix paths)
        (if (seq-every-p (apply-partially #'string-match-p "^[0-9]+\]$") paths)
            ;; We are in an array, and indexes are numbers like "42]". We should sort them low to high.
            (lambda (x y) (< (string-to-number x) (string-to-number y)))