add --force option to raco pollen render, take 2

pollen/private/command.rkt

@@ -1,4 +1,4 @@
-#lang racket/base
+#lang debug racket/base
 (require racket/file
          racket/path
          racket/vector
@@ -104,6 +104,7 @@ version                print the version" (current-server-port) (make-publish-di
   (define render-with-subdirs? (make-parameter #f))
   (define render-parallel? (make-parameter #f))
   (define special-output? (make-parameter #f))
+  (define force-render? (make-parameter #f))
   (define parsed-args
     (command-line #:program "raco pollen render"
                   #:argv (vector-drop (current-command-line-arguments) 1) ; snip the 'render' from the front
@@ -113,6 +114,7 @@ version                print the version" (current-server-port) (make-publish-di
                   [("-r" "--recursive") "Render subdirectories recursively"
                                         (render-with-subdirs? 'recursive)]
                   [("-s" "--subdir") "Render subdirectories nonrecursively" (render-with-subdirs? 'include)]
+                  [("-f" "--force") "Force render" (force-render? #true)]
                   #:once-any
                   [("-d" "--dry-run") "Print paths that would be rendered" (special-output? 'dry-run)]
                   [("-n" "--null") "Suppress file output" (special-output? 'null)]
@@ -122,7 +124,15 @@ version                print the version" (current-server-port) (make-publish-di
                   #:args other-args
                   other-args))
 
+  (define timestamp (current-seconds)) ; keeps timestamp consistent through whole render
   (define (handle-batch-render paths)
+    (when (force-render?)
+      ;; forcing works like `touch`: updates the mod date of the files,
+      ;; which invalidates any cached results.
+      (for* ([path (in-list paths)]
+             [sp (in-value (get-source path))]
+             #:when sp)
+        (file-or-directory-modify-seconds sp timestamp)))
     (apply render-batch (map very-nice-path paths) #:parallel (render-parallel?) #:special (special-output?)))
   
   (parameterize ([current-poly-target (render-target-wanted)]) ;; applies to both cases

pollen/private/ts.rktd

@@ -1 +1 @@
-1588261516
+1588526073

pollen/scribblings/raco.scrbl

@@ -83,6 +83,8 @@ This command can be invoked two ways: in source mode or directory mode.
 
 In both modes, the optional @exec{--dry-run} or @exec{-d} switch prints the paths that would be rendered by this command without actually doing so. 
 
+In both modes, the optional @exec{--force} or @exec{-f} switch forces a fresh render from source, even if the file is already cached, by updating the modification date of the file (à la @exec{touch}). Thus, if modification dates are important to you, don't use this option.
+
 In both modes, the optional @exec{--null} or @exec{-n} switch renders as usual, but doesn't write any files. (Convenient if you're arranging special render behavior, for instance writing to a database or network server.)