further racer-debug work

racer.el

@@ -100,35 +100,53 @@ If nil, we will query $CARGO_HOME at runtime."
   (let ((root (locate-dominating-file (or buffer-file-name default-directory) "Cargo.toml")))
     (and root (file-truename root))))
 
-;; Variables used by `racer-debug'.
-(defvar racer--last-directory nil)
-(defvar racer--last-src-path nil)
-(defvar racer--last-cargo-home nil)
-(defvar racer--last-command nil)
-(defvar racer--last-args nil)
+(defvar racer--prev-state nil)
 
 (defun racer-debug ()
-  "Open a buffer with debug information necessary for filing a bug report."
+  "Open a buffer describing the last racer command run.
+Helps users find configuration issues, or file bugs on
+racer or racer.el."
   (interactive)
   (let ((buf (get-buffer-create "*racer-debug*"))
         (inhibit-read-only t))
     (with-current-buffer buf
       (erase-buffer)
       (setq buffer-read-only t)
-      (insert "Configuration:\n")
-      (insert "default-directory: " racer--last-directory "\n")
-      (insert "RUST_SRC_PATH: " racer--last-src-path "\n")
-      (insert "CARGO_HOME: " racer--last-cargo-home "\n\n")
-      (insert "Command run:\n")
-      (insert "$ " racer-cmd " " racer--last-command " " (s-join " " racer--last-args))
-      (insert "\n\nPlease report bugs ")
-      (insert (racer--url-button "on GitHub" "https://github.com/racer-rust/emacs-racer/issues/new")
-              "."))
+      (let* ((process-environment
+              (plist-get racer--prev-state :process-environment))
+             (rust-src-path-used
+              (--first (s-prefix-p "RUST_SRC_PATH=" it) process-environment))
+             (cargo-home-used
+              (--first (s-prefix-p "CARGO_HOME=" it) process-environment))
+             (stdout (plist-get racer--prev-state :stdout))
+             (stderr (plist-get racer--prev-state :stderr)))
+        (insert
+         "The last racer command was:\n\n"
+         (format "$ cd %s\n"
+                 (plist-get racer--prev-state :default-directory))
+         (format "$ export %s\n" cargo-home-used)
+         (format "$ export %s\n" rust-src-path-used)
+         (format "$ %s %s\n\n"
+                 (plist-get racer--prev-state :program)
+                 (s-join " " (plist-get racer--prev-state :args)))
+         (format "This command terminated with exit code %s.\n\n"
+                 (plist-get racer--prev-state :exit-code))
+         (if (s-blank? stdout)
+             "No output on stdout.\n\n"
+           (format "stdout:\n\n%s\n\n" (s-trim-right stdout)))
+         (if (s-blank? stderr)
+             "No output on stderr.\n\n"
+           (format "stderr:\n\n%s\n\n" (s-trim-right stderr)))
+         "Please report bugs "
+         (racer--url-button "on GitHub" "https://github.com/racer-rust/emacs-racer/issues/new")
+         ".")))
     (switch-to-buffer buf)
     (goto-char (point-min))))
 
 (defun racer--call (command &rest args)
-  "Call racer command COMMAND with args ARGS."
+  "Call racer command COMMAND with args ARGS.
+Return stdout if COMMAND exits normally, otherwise show an
+error."
   (let ((rust-src-path (or racer-rust-src-path (getenv "RUST_SRC_PATH")))
         (cargo-home (or racer-cargo-home (getenv "CARGO_HOME"))))
     (when (null rust-src-path)
@@ -138,14 +156,12 @@ If nil, we will query $CARGO_HOME at runtime."
                                         (format "RUST_SRC_PATH=%s" (expand-file-name rust-src-path))
                                         (format "CARGO_HOME=%s" (expand-file-name cargo-home)))
                                        process-environment)))
-      ;; Save variables for `racer-debug'.
-      (setq racer--last-directory default-directory)
-      (setq racer--last-src-path rust-src-path)
-      (setq racer--last-cargo-home cargo-home)
-      (setq racer--last-command command)
-      (setq racer--last-args args)
-      ;; Invoke racer.
-      (apply #'process-lines racer-cmd command args))))
+      (-let [(exit-code stdout _stderr)
+             (racer--shell-command racer-cmd (cons command args))]
+        (unless (zerop exit-code)
+          (user-error "%s exited with %s. `M-x racer-debug' for more info"
+                      racer-cmd exit-code))
+        stdout))))
 
 (defmacro racer--with-temporary-file (path-sym &rest body)
   "Create a temporary file, and bind its path to PATH-SYM.
@@ -176,17 +192,29 @@ Return a list (exit-code stdout stderr)."
                      nil args))
         (setq stdout (buffer-string)))
       (setq stderr (racer--slurp tmp-file-for-stderr))
+      (setq racer--prev-state
+            (list
+             :program program
+             :args args
+             :exit-code exit-code
+             :stdout stdout
+             :stderr stderr
+             :default-directory default-directory
+             :process-environment process-environment))
       (list exit-code stdout stderr))))
 
 (defun racer--call-at-point (command)
-  "Call racer command COMMAND at point of current buffer."
+  "Call racer command COMMAND at point of current buffer.
+Return a list of all the lines returned by the command."
   (racer--with-temporary-file tmp-file
     (write-region nil nil tmp-file nil 'silent)
-    (racer--call command
-                 (number-to-string (line-number-at-pos))
-                 (number-to-string (racer--current-column))
-                 (buffer-file-name)
-                 tmp-file)))
+    (s-lines
+     (s-trim-right
+      (racer--call command
+                   (number-to-string (line-number-at-pos))
+                   (number-to-string (racer--current-column))
+                   (buffer-file-name)
+                   tmp-file)))))
 
 (defun racer--read-rust-string (string)
   "Convert STRING, a rust string literal, to an elisp string."