Protect against empty commands

Improves the code so that empty strings are not sent to the process anymore. It
also avoids trimming \t because they are actually used by some REPL.

Author: arichiardi

inf-clojure.el

@@ -256,15 +256,28 @@ It requires a REPL PROC for inspecting the correct type."
     inf-clojure-repl-type))
 
 (defun inf-clojure--single-linify (string)
-  "Convert a multi-line STRING in a single-line STRING."
-  (replace-regexp-in-string "[[:space:]\\|\n]+" " " string))
+  "Convert a multi-line STRING in a single-line STRING.
+It also reduces/adds redundant whitespace for readability.  Note
+that this function will transform the empty string in \" \" (it
+adds an empty space)."
+  (replace-regexp-in-string "[ \\|\n]+" " " string))
+
+(defun inf-clojure--trim-newline-right (string)
+  "Trim newlines (only) in STRING."
+  (if (string-match "\n+\\'" string)
+      (replace-match "" t t string)
+    string))
 
 (defun inf-clojure--sanitize-command (command)
   "Sanitize COMMAND for sending it to a process.
 An example of things that this function does is to add a final
-newline at the end of the form."
-  (concat (string-trim-right (inf-clojure--single-linify command))
-          "\n"))
+newline at the end of the form.  Return an empty string if the
+sanitized command is empty."
+  (let* ((linified (inf-clojure--single-linify command))
+         (sanitized (inf-clojure--trim-newline-right linified)))
+    (if (or (string-blank-p linified) (string-blank-p sanitized))
+        ""
+      (concat sanitized "\n"))))
 
 (defun inf-clojure--send-string (proc string)
   "A custom `comint-input-sender` / `comint-send-string`.
@@ -275,7 +288,8 @@ always be preferred over `comint-send-string`.  It delegates to
 the string for evaluation.  Refer to `comint-simple-send` for
 customizations."
   (inf-clojure--set-repl-type proc)
-  (comint-simple-send proc string))
+  (when (> (length string) 0)
+    (comint-simple-send proc string)))
 
 (defcustom inf-clojure-load-form "(clojure.core/load-file \"%s\")"
   "Format-string for building a Clojure expression to load a file.
@@ -1041,31 +1055,32 @@ If BEG-REGEXP is nil, the result string will start from (point)
 in the results buffer.  If END-REGEXP is nil, the result string
 will end at (point-max) in the results buffer.  It cuts out the
 output from and including the `inf-clojure-prompt`."
-  (inf-clojure--log-string command "----CMD->")
-  (let ((work-buffer inf-clojure--redirect-buffer-name))
-    (save-excursion
-      (set-buffer (get-buffer-create work-buffer))
-      (erase-buffer)
-      (comint-redirect-send-command-to-process
-       (inf-clojure--sanitize-command command) work-buffer process nil t)
-      ;; Wait for the process to complete
-      (set-buffer (process-buffer process))
-      (while (and (null comint-redirect-completed)
-                  (accept-process-output process 1 0 t))
-        (sleep-for 0.01))
-      ;; Collect the output
-      (set-buffer work-buffer)
-      (goto-char (point-min))
-      (let* ((buffer-string (buffer-substring-no-properties (point-min) (point-max)))
-             (boundaries (inf-clojure--string-boundaries buffer-string inf-clojure-prompt beg-regexp end-regexp))
-             (beg-pos (car boundaries))
-             (end-pos (car (cdr boundaries)))
-             (prompt-pos (car (cdr (cdr boundaries))))
-             (response-string (substring buffer-string beg-pos (min end-pos prompt-pos))))
-        (inf-clojure--log-string buffer-string "<-BUF----")
-        (inf-clojure--log-string boundaries "<-BND----")
-        (inf-clojure--log-string response-string "<-RES----")
-        response-string))))
+  (let ((work-buffer inf-clojure--redirect-buffer-name)
+        (sanitized-command (inf-clojure--sanitize-command command)))
+    (when (not (string-empty-p sanitized-command))
+      (inf-clojure--log-string command "----CMD->")
+      (save-excursion
+        (set-buffer (get-buffer-create work-buffer))
+        (erase-buffer)
+        (comint-redirect-send-command-to-process sanitized-command work-buffer process nil t)
+        ;; Wait for the process to complete
+        (set-buffer (process-buffer process))
+        (while (and (null comint-redirect-completed)
+                    (accept-process-output process 1 0 t))
+          (sleep-for 0.01))
+        ;; Collect the output
+        (set-buffer work-buffer)
+        (goto-char (point-min))
+        (let* ((buffer-string (buffer-substring-no-properties (point-min) (point-max)))
+               (boundaries (inf-clojure--string-boundaries buffer-string inf-clojure-prompt beg-regexp end-regexp))
+               (beg-pos (car boundaries))
+               (end-pos (car (cdr boundaries)))
+               (prompt-pos (car (cdr (cdr boundaries))))
+               (response-string (substring buffer-string beg-pos (min end-pos prompt-pos))))
+          (inf-clojure--log-string buffer-string "<-BUF----")
+          (inf-clojure--log-string boundaries "<-BND----")
+          (inf-clojure--log-string response-string "<-RES----")
+          response-string)))))
 
 (defun inf-clojure--nil-string-match-p (string)
   "Return true iff STRING is not nil.