add dry-run switch to raco pollen publish

pollen/private/command.rkt

@@ -207,12 +207,14 @@ version                print the version" (current-server-port) (make-publish-di
   (define command-name ; either "publish" or "clone"
     (vector-ref (current-command-line-arguments) 0))
   (define force-target-overwrite? (make-parameter #true))
+  (define dry-run? (make-parameter #false))
   (define other-args (command-line
                       ;; drop command name
                       #:argv (vector-drop (current-command-line-arguments) 1)
                       #:once-each
                       [("-c" "--confirm") "Confirm overwrite of existing dest dir"
                                           (force-target-overwrite? #f)]
+                      [("-d" "--dry-run") "Check paths that would be published" (dry-run? #true)]
                       #:args other-args
                       other-args))
   ;; other-args looks like (list [maybe-source-dir-arg] [maybe-dest-dir-arg])
@@ -235,7 +237,6 @@ version                print the version" (current-server-port) (make-publish-di
   (when (equal? dest-dir (current-directory))
     (error 'publish "aborted because destination directory for publishing (~a) can't be the same as current directory (~a)" dest-dir (current-directory)))
   
-  (message (string-append (format "publishing from ~a to ~a ..." source-dir dest-dir)))
   (define do-publish-operation?
     (or (not (directory-exists? dest-dir))
         (force-target-overwrite?)
@@ -244,6 +245,20 @@ version                print the version" (current-server-port) (make-publish-di
           (case (read)
             [(y yes) #true]
             [else #false]))))
+  (cond
+    [dry-run?
+     (message "publish: start dry run")
+     (message (format "would publish from ~a to ~a" source-dir dest-dir))
+     (cond
+       [(directory-exists? dest-dir)
+        (message (string-append (format "directory ~a exists (but can be overwritten)" dest-dir)))]
+       [(directory-exists? (simplify-path (build-path dest-dir "..")))
+        (message (string-append (format "directory ~a does not exist (but can be created)" dest-dir)))]
+       [else
+        (raise-user-error 'publish "dry run failure: directory path ~a is defective (neither directory nor parent directory exists)" dest-dir)])
+     (message "publish: end dry run")]
+    [else
+     (message (string-append (format "publishing from ~a to ~a ..." source-dir dest-dir)))
      (cond
        [do-publish-operation?
         (when (directory-exists? dest-dir)
@@ -258,7 +273,7 @@ version                print the version" (current-server-port) (make-publish-di
             (and (omitted-path? p) (not (extra-path? p))))
           (for-each delete-it! (find-files delete-from-publish-dir? dest-dir)))
         (message "publish completed")]
-    [else (message "publish aborted")]))
+       [else (message "publish aborted")])]))
 
 (define (handle-unknown command)
   (match command

pollen/private/ts.rktd

@@ -1 +1 @@
-1582236997
+1582753630

pollen/scribblings/raco.scrbl

@@ -159,6 +159,7 @@ You can determine the default publishing destination for a project by overriding
 
 Certain files and directories are automatically omitted from the published directory, including Racket and Pollen sources, Pollen caches, and source-control directories (like @tt{.git} and @tt{.svn}). You can omit other files by overriding @racket[default-omitted-path?]. You can override these omissions — that is, force a path to be published — by overriding @racket[default-extra-path?].
 
+The optional @exec{--dry-run} or @exec{-d} switch prints the source and destination directories for publishing without actually doing so. If the destination-directory path cannot be created, an error will arise.
 
 @section{@exec{raco pollen setup}}