enable at-reader in `br` languages

beautiful-racket-lib/br/get-info.rkt

@@ -17,7 +17,19 @@
                                                       "until") 'define]
                                                     [else #f])))))
 
-(define (br-get-info key default default-filter)
+(define (br-get-info key default-value proc)
+  (define (fallback) (if proc (proc key default-value) default-value))
+  (define (try-dynamic-require lib export)
+    (with-handlers ([exn:missing-module?
+                     (λ (x) (case key
+                              [(drracket:indentation) indenter]
+                              [else (fallback)]))])
+      (dynamic-require lib export)))
   (case key
-    [(drracket:indentation) indenter]
-    [else (default-filter key default)]))
+    [(color-lexer)
+     (try-dynamic-require 'syntax-color/scribble-lexer 'scribble-lexer)]
+    [(drracket:indentation)
+     (try-dynamic-require 'scribble/private/indentation 'determine-spaces)]
+    [(drracket:keystrokes)
+     (try-dynamic-require 'scribble/private/indentation 'keystrokes)]
+    [else (fallback)]))

beautiful-racket-lib/br/main.rkt

@@ -22,4 +22,6 @@
 (module reader syntax/module-reader
   #:language 'br
   #:info br-get-info
-  (require br/get-info))
+  #:read at:read
+  #:read-syntax at:read-syntax
+  (require br/get-info (prefix-in at: scribble/reader)))

beautiful-racket-lib/br/quicklang.rkt

@@ -5,11 +5,13 @@
          (for-syntax (all-from-out sugar/debug)))
 
 (define-macro (quicklang-mb . EXPRS)
-  #`(#%module-begin
+  #'(#%module-begin
      (provide #%top #%app #%datum #%top-interaction)
      . EXPRS))
 
 (module reader syntax/module-reader
   #:language 'br/quicklang
   #:info br-get-info
-  (require br/get-info))
+  #:read at:read
+  #:read-syntax at:read-syntax
+  (require br/get-info (prefix-in at: scribble/reader)))