use submodule for settable values

scribblings/world.scrbl

@@ -32,26 +32,28 @@ A parameter that determines whether the @racket[world:directory-require] file is
 
 
 
-@section{Values that can be overwritten with @racket[local:]}
+@section{Settable values}
 
-These values can be changed by overriding them in your @racket["directory-require.rkt"] source file. Use @racket[define] to make a variable with the same name as the one in @racket[pollen/world], but with the prefix @racket[local:] instead of @racket[world:]. Assign it whatever value you like. When Pollen runs, these definitions will supersede those in @racket[pollen/world].
+These values can be changed by overriding them in your @racket["directory-require.rkt"] source file. Within this file, create a submodule called @racket[config]. (More about @secref["submodules" #:doc '(lib "scribblings/guide/guide.scrbl")].) Then within this submodule, use @racket[define] to make variable with the same name as the one in @racket[pollen/world], but without the @racket[world:] prefix. Assign it whatever value you like. Repeat as needed. When Pollen runs, these definitions will supersede those in @racket[pollen/world].
 
-For instance, suppose you wanted the main export of every Pollen source file to be called @racket[van-halen] rather than @racket[doc], the extension of Pollen markup files to be @racket[rock] rather than @racket[pm], and the command character to be @litchar{🎸} instead of @litchar{◊}. Your @racket["directory-require.rkt"] would include these defintions:
+For instance, suppose you wanted the main export of every Pollen source file to be called @racket[van-halen] rather than @racket[doc], the extension of Pollen markup files to be @racket[.rock] rather than @racket[.pm], and the command character to be @litchar{🎸} instead of @litchar{◊}. Your @racket["directory-require.rkt"] would look like this:
 
 @fileblock["directory-require.rkt" 
 @codeblock{
 #lang racket/base
+
+(module config racket/base
   (provide (all-defined-out))
-(define local:main-export 'van-halen)
+  (define main-export 'van-halen)
-(define local:markup-source-ext 'rock)
+  (define markup-source-ext 'rock)
-(define local:command-char #\🎸)
+  (define command-char #\🎸))
 }]
 
 Though any of the values below can be overridden, it may not always be wise to do so. For instance, if you redefined @racket[world:fallback-template-prefix], you would simply break the fallback-template mechanism, because it would look for files that don't exist. But we don't live in a nanny state, so you are entrusted to say what you mean and accept the consequences.
 
 Of course, you can restore the defaults simply by deleting these defined values from @racket["directory-require.rkt"].
 
-These overridable values also come with a corresponding @racket[get-] function that will return the @racket[local:] value if it exists, otherwise the @racket[world:] value. In the example above, @racket[world:command-char] would be @litchar{◊} no matter what, but @racket[world:get-command-char] would return @litchar{🎸}.
+These settable values also come with a corresponding @racket[get-] function that will return the @racket[config] value if it exists, otherwise the @racket[world:] value. In the example above, @racket[world:command-char] would be @litchar{◊} no matter what, but @racket[world:get-command-char] would return @litchar{🎸}.
 
 
 @defoverridable[default-port integer?]{

test/data/override/directory-require.rkt

@@ -4,15 +4,17 @@
 (define (root . xs)
   `(rootover ,@xs))
 
-(define local:pollen-version "42")
+(module config racket/base
+  (provide (all-defined-out))
+  (define pollen-version "42")
   
-(define local:preproc-source-ext 'ppover)
+  (define preproc-source-ext 'ppover)
-(define local:markup-source-ext 'pmover)
+  (define markup-source-ext 'pmover)
-(define local:markdown-source-ext 'pmdover)
+  (define markdown-source-ext 'pmdover)
-(define local:null-source-ext 'p)
+  (define null-source-ext 'p)
-(define local:pagetree-source-ext 'ptreeover)
+  (define pagetree-source-ext 'ptreeover)
   
-(define local:command-char #\∆)
+  (define command-char #\∆)
-(define local:main-export 'docover)
+  (define main-export 'docover)
-(define local:meta-export 'metasover)
+  (define meta-export 'metasover)
-(define local:meta-tag-name 'metaover)
+  (define meta-tag-name 'metaover))

world.rkt

@@ -11,19 +11,19 @@
   (build-path (current-project-root) directory-require))
 
 ;; parameters should not be made settable.
+(define-for-syntax config-submodule-name 'config)
 (define-syntax (define-settable stx)
   (syntax-case stx ()
     [(_ name default-value)
      (with-syntax ([base-name (format-id stx "~a" #'name)]
-                   [local:name (format-id stx "local:~a" #'name)]
                    [get-name (format-id stx "get-~a" #'name)]
+                   [config-submodule (format-id stx "~a" config-submodule-name)]
                    [fail-thunk-name (format-id stx "fail-thunk-~a" #'name)] )
        #'(begin
            (define base-name default-value)
            (define fail-thunk-name (λ _ base-name))
            (define get-name (λ _ (with-handlers ([exn:fail? fail-thunk-name])
-                                     (dynamic-require (get-path-to-override) 'local:name fail-thunk-name))))))]))
+                                    (dynamic-require `(submod ,(get-path-to-override) config-submodule) 'base-name fail-thunk-name))))))]))
-                                     
 
 (define-settable pollen-version "0.001")