made 23238 stable w/ shared file prefix; Closes PR 12093 again

collects/htdp/convert.rkt

@@ -3,7 +3,7 @@
 ;; ---------------------------------------------------------------------------------------------------
 ;; functions that demonstrate how one and the same function can be used in three different contexts
 
-(require mzlib/etc lang/prim htdp/error)
+(require mzlib/etc lang/prim lang/htdp-langs-save-file-prefix htdp/error )
 
 (provide-higher-order-primitive convert-gui (f2c))
 (provide-higher-order-primitive convert-repl (f2c))
@@ -243,7 +243,7 @@
              "first" in)
   (check-proc 'convert-file f 1 "convert-file" "one argument")
   (check-arg 'convert-file (string? out) "string" "third" out)
-  ;; [IPort -> Void] -> Void 
+  ;; [ -> Void] -> Void 
   ;; perform the actual conversion on the file after optionally reading a prelude 
   (define (convert-file prefix)
     (with-output-to-file out #:exists 'replace 
@@ -254,20 +254,16 @@
                      (define reader-exception? (regexp-match "#reader" message))
                      (cond
                        [reader-exception? 
-                        (with-handlers ((exn:fail:read? 
-                                         (lambda (x)
-                                           (error 'convert-file CONVERT-FILE-MESSAGE))))
+                        (with-handlers ((exn:fail:read? (lambda (y) (raise x))))
                           (convert-file
                            (lambda ()
-                             ;; this assumes that DrRacket adds three lines of header
-                             ;; material to files saved in a Menu-selected language 
-                             (read-line)
-                             (read-line)
-                             (read-line))))]
+			     (unless (htdp-file-prefix? (current-input-port)) (raise x)))))]
                        [else (raise x)]))))
     (convert-file void)))
 
-;; make-reader-for-f : [Number -> Number] [IPort -> Void] -> [ -> void]
+(define *debug (current-output-port))
+
+;; make-reader-for-f : [Number -> Number] [ -> Void] -> [ -> void]
 ;; make-reader-for-f creates a function that reads numbers from a file
 ;; converts them according to f, and prints the results
 ;; effect: if any of the S-expressions in the file aren't numbers or
@@ -285,4 +281,4 @@
          (if (number? out) (printf "~s\n" out) (error 'convert OUT-ERROR out))
          (read-until-eof)]
         [else (error 'convert IN-ERROR in)])))
-  read-until-eof)
+  read-until-eof)

collects/htdp/tests/convert-drracket-error.rkt

@@ -6,8 +6,7 @@
 
 (convert-file "convert-drracket-non-error.txt" Fahrenheit->Celsius "out.dat")
 
-(with-handlers ((exn? (lambda (x)
-                        (unless (cons? (regexp-match "DrRacket" (exn-message x)))
-                          (error 'test "something went wrong with the test (1)")))))
+(with-handlers ((exn:fail:read? void))
+  "The input file contains a bad header. The next line should raise an exn."
   (convert-file "convert-drracket-error.txt" Fahrenheit->Celsius "out.dat")
-  (raise `(test "something went wrong with the test (2)")))
+  (raise `(test "this test should have failed but didn't")))

collects/htdp/tests/convert-drracket-non-error.txt

@@ -1,5 +1,4 @@
 ;; The first three lines of this file were inserted by DrRacket. They record metadata
 ;; about the language level of this file in a form that our tools can easily process.
-#reader(lib "htdp-beginner-reader.ss" "lang")((modname convert-drracket-error) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ())))
-
+#reader(lib "htdp-beginner-reader.ss" "lang")((modname convert-drracket-non-error) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ())))
 214

collects/lang/htdp-langs-save-file-prefix.rkt

@@ -1,11 +1,16 @@
 #lang racket/base
-(require racket/contract
+
+;; ---------------------------------------------------------------------------------------------------
+;; exports the header for a file saved from a drracket buffer in a menu-selected teaching language 
+
+(require racket/contract 
          racket/port)
 
 (provide/contract
  [htdp-save-file-prefix (listof string?)]
  [htdp-file-prefix? (-> input-port? boolean?)])
 
+
 (define htdp-save-file-prefix
   (list ";; The first three lines of this file were inserted by DrRacket. They record metadata"
         ";; about the language level of this file in a form that our tools can easily process."))
@@ -27,8 +32,7 @@
     (cond
       [(null? prefix)
        (define l (read-line port 'any))
-       (and (string? l)
-            (regexp-match #rx"^#reader" l))]
+       (and (string? l) (pair? (regexp-match #rx"^#reader" l)))]
       [else
        (define l (read-line port 'any))
        (and (string? l)