From 015eab3dd8a55c29e463608b29a00e4e449036ec Mon Sep 17 00:00:00 2001
From: Arun Isaac
Date: Mon, 14 Mar 2022 14:19:17 +0530
Subject: bin: Raise exception on missing file.

* bin/tissue: Import (rnrs conditions).
(tissue-edit, tissue-show): Raise exception on missing file.
---
 bin/tissue | 104 ++++++++++++++++++++++++++++++++++---------------------------
 1 file changed, 58 insertions(+), 46 deletions(-)

diff --git a/bin/tissue b/bin/tissue
index 94f0188..ff593c6 100755
--- a/bin/tissue
+++ b/bin/tissue
@@ -19,7 +19,8 @@
 ;;; You should have received a copy of the GNU General Public License
 ;;; along with tissue.  If not, see <https://www.gnu.org/licenses/>.
 
-(import (rnrs io ports)
+(import (rnrs conditions)
+        (rnrs io ports)
         (srfi srfi-1)
         (srfi srfi-26)
         (srfi srfi-37)
@@ -278,9 +279,14 @@ Start $EDITOR to edit issue #ISSUE-NUMBER.
      (unless (getenv "EDITOR")
        (error "Please set the EDITOR environment variable to your favorite editor. For example,
 export EDITOR=emacsclient"))
-     (invoke (getenv "EDITOR")
-             (issue-file (list-ref (issues)
-                                   (1- (string->number issue-number))))))))
+     (let ((issue-file (issue-file (list-ref (issues)
+                                             (1- (string->number issue-number))))))
+       ;; Files may be renamed or deleted, but not
+       ;; committed. Therefore, only read the file if it exists.
+       (if (file-exists? issue-file)
+           (invoke (getenv "EDITOR") issue-file)
+           (raise-exception (make-message-condition
+                             (string-append "No such file or directory: " issue-file))))))))
 
 (define tissue-show
   (match-lambda*
@@ -291,48 +297,54 @@ Show the text of issue #ISSUE-NUMBER.
 "
              (command-line-program)))
     ((issue-number)
-     (call-with-input-file (issue-file (list-ref (issues)
-                                                 (1- (string->number issue-number))))
-       (lambda (port)
-         (port-transduce
-          (compose
-           ;; Detect preformatted text blocks.
-           (tfold (match-lambda*
-                    (((pre? . _) line)
-                     (cons (if (string-prefix? "```" line)
-                               (not pre?)
-                               pre?)
-                           line)))
-                  (cons #f #f))
-           (tmap (lambda (pre?+line)
-                   (match pre?+line
-                     ((pre? . line)
-                      (cond
-                       ;; Print headlines in bold.
-                       ((string-prefix? "#" line)
-                        (display (bold line)))
-                       ;; Print lists in cyan.
-                       ((string-prefix? "*" line)
-                        (display (cyan line)))
-                       ;; Print links in cyan, but only the actual
-                       ;; link, and not the => prefix or the label.
-                       ((string-match "^(=>[ \t]*)([^ ]*)([^\n]*)" line)
-                        => (lambda (m)
-                             (display (match:substring m 1))
-                             (display (cyan (match:substring m 2)))
-                             (display (match:substring m 3))))
-                       ;; Print preformatted text backticks in
-                       ;; magenta.
-                       ((string-prefix? "```" line)
-                        (display (magenta line)))
-                       (else
-                        ;; If part of preformatted block, print in
-                        ;; magenta. Else, print in default color.
-                        (display (if pre? (magenta line) line))))))
-                   (newline))))
-          (const #t)
-          get-line-dos-or-unix
-          port))))))
+     (let ((issue-file (issue-file (list-ref (issues)
+                                             (1- (string->number issue-number))))))
+       ;; Files may be renamed or deleted, but not
+       ;; committed. Therefore, only read the file if it exists.
+       (if (file-exists? issue-file)
+           (call-with-input-file (issue-file issue)
+             (lambda (port)
+               (port-transduce
+                (compose
+                 ;; Detect preformatted text blocks.
+                 (tfold (match-lambda*
+                          (((pre? . _) line)
+                           (cons (if (string-prefix? "```" line)
+                                     (not pre?)
+                                     pre?)
+                                 line)))
+                        (cons #f #f))
+                 (tmap (lambda (pre?+line)
+                         (match pre?+line
+                           ((pre? . line)
+                            (cond
+                             ;; Print headlines in bold.
+                             ((string-prefix? "#" line)
+                              (display (bold line)))
+                             ;; Print lists in cyan.
+                             ((string-prefix? "*" line)
+                              (display (cyan line)))
+                             ;; Print links in cyan, but only the actual
+                             ;; link, and not the => prefix or the label.
+                             ((string-match "^(=>[ \t]*)([^ ]*)([^\n]*)" line)
+                              => (lambda (m)
+                                   (display (match:substring m 1))
+                                   (display (cyan (match:substring m 2)))
+                                   (display (match:substring m 3))))
+                             ;; Print preformatted text backticks in
+                             ;; magenta.
+                             ((string-prefix? "```" line)
+                              (display (magenta line)))
+                             (else
+                              ;; If part of preformatted block, print in
+                              ;; magenta. Else, print in default color.
+                              (display (if pre? (magenta line) line))))))
+                         (newline))))
+                (const #t)
+                get-line-dos-or-unix
+                port)))
+           (raise-exception (make-message-condition
+                             (string-append "No such file or directory: " issue-file))))))))
 
 (define (print-usage)
   (format #t "Usage: ~a COMMAND [OPTIONS] [ARGS]
-- 
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