Added the ability for #lang-based languages to specify when an expression should be submitted at the prompt

collects/drracket/private/drsig.rkt

@@ -119,6 +119,7 @@
    system-custodian
    system-eventspace
    system-namespace
+   system-security-guard
    first-dir))
 
 (define-signature drracket:language-configuration-cm^

collects/drracket/private/init.rkt

@@ -28,6 +28,8 @@
   (define error-display-handler-message-box-title
     (make-parameter (string-constant drscheme-internal-error)))
   
+  (define system-security-guard (current-security-guard))
+  
   ;; override error-display-handler to duplicate the error
   ;; message in both the standard place (as defined by the
   ;; current error-display-handler) and in a message box

collects/drracket/private/module-language.rkt

@@ -6,6 +6,7 @@
          racket/list
          racket/path
          racket/contract
+         racket/sandbox
          mred
          compiler/embed
          compiler/cm
@@ -29,7 +30,8 @@
   
   (define module-language<%>
     (interface ()
-      get-users-language-name))
+      get-users-language-name
+      get-language-info))
   
   ;; add-module-language : -> void
   ;; adds the special module-only language to drscheme
@@ -58,6 +60,26 @@
   (define (module-mixin %)
     (class* % (drracket:language:language<%> module-language<%>)
       
+      (define language-info #f) ;; a result from module-compiled-language-info
+      (define sandbox #f)       ;; a sandbox for querying the language-info
+      (define/public (get-language-info key default)
+        (init-sandbox)
+        (cond
+          [(and language-info sandbox)
+           (let ([mp (vector-ref language-info 0)]
+                 [name (vector-ref language-info 1)]
+                 [val (vector-ref language-info 2)])
+             (call-in-sandbox-context
+              sandbox
+              (λ ()
+                (parameterize ([current-security-guard drracket:init:system-security-guard])
+                  (((dynamic-require mp name) val) key default)))))]
+          [else default]))
+      (define (init-sandbox)
+        (unless sandbox
+          (when language-info
+            (set! sandbox (make-evaluator 'racket/base)))))
+      
       (inherit get-language-name)
       (define/public (get-users-language-name defs-text)
         (let* ([defs-port (open-input-text-editor defs-text)]
@@ -191,6 +213,12 @@
       
       (define/override (on-execute settings run-in-user-thread)
         (super on-execute settings run-in-user-thread)
+        
+        ;; reset the language info so that if the module is illformed, 
+        ;; we don't save the language info from the last run
+        (set! language-info #f)
+        (set! sandbox #f)
+        
         (run-in-user-thread
          (λ ()
            (current-command-line-arguments
@@ -323,6 +351,9 @@
           (check-interactive-language))
         (define (*do-module-specified-configuration)
           (let ([info (module->language-info modspec #t)])
+            (parameterize ([current-eventspace drracket:init:system-eventspace])
+              (queue-callback
+               (λ () (set! language-info info))))
             (when info
               (let ([get-info
                      ((dynamic-require (vector-ref info 0)

collects/drracket/private/rep.rkt

@@ -993,8 +993,22 @@ TODO
             (send key get-control-down)
             (send key get-alt-down)
             (and prompt-position
-                 (only-whitespace-after-insertion-point)
-                 (submit-predicate this prompt-position))))
+                 (let ([lang (drracket:language-configuration:language-settings-language user-language-settings)])
+                   (cond
+                     [(is-a? lang drracket:module-language:module-language<%>)
+                      (let ([pred 
+                             (send lang get-language-info 
+                                   'drracket:submit-predicate
+                                   (λ (editor prompt-position)
+                                     (and (only-whitespace-after-insertion-point)
+                                          (submit-predicate this prompt-position))))])
+                        (pred 
+                         ;; no good! giving away the farm here. need to hand over a proxy that is limited to just read access
+                         this
+                         prompt-position))]
+                     [else
+                      (and (only-whitespace-after-insertion-point)
+                           (submit-predicate this prompt-position))])))))
       
       (define/private (only-whitespace-after-insertion-point)
         (let ([start (get-start-position)]

collects/scribblings/tools/tools.scrbl

@@ -465,6 +465,25 @@ uses Racket mode.
 
 @section{Language-specific capabilities}
 
+@subsection{Customizing DrRacket's behavior}
+
+When using the language declared in the source, DrRacket queries  that
+language via @racket[module-compiled-language-info] to determine
+if an expression in the interactions window is ready to be submitted
+to the evaluator (when the user types return).
+The info procedure is passed @racket['drracket:submit-predicate] 
+and should return a function with this contract:
+@racketblock[(-> (is-a?/c text%)
+                 number?
+                 boolean?)]
+This function is called with the interactions window's editor object
+the first position in the editor after the prompt and should return
+a boolean indicating if the expression should be evaluated.
+This function is called in sandbox, but with no filesystem or networking 
+limits.
+
+@subsection{Customizing DrRacket's GUI}
+
 DrRacket's capability interface provides a mechanism for
 tools to allow languages to hide their GUI interface, if the
 tool does not apply to the language. Tools register