Try to avoid a possible error in the normalize-paste code

judging from a runtime error I saw in DrRacket, it seems likely
that this code causes the next/prev links to break and then things
go wrong. I can't seem to make a test case that causes the problem,
but if that is the problem, then this should fix it (as we now
postpone modifications to the editor until after we know what
all of them are instead of interleaving the changes to the buffer
with a traversal that finds the changes to make)

Author: rfindler

gui-lib/framework/private/text-normalize-paste.rkt

@@ -91,6 +91,7 @@
             (define len (list-ref insertion 1))
             (split-snip start)
             (split-snip (+ start len))
+            (define changes-to-make '())
             (let loop ([snip (find-snip (+ start len) 'before-or-none)])
               (when snip
                 (define prev-snip (send snip previous))
@@ -105,7 +106,11 @@
                         (unless (ask-normalize?) (abort)))
                       (define snip-pos (get-snip-position snip))
                       (delete snip-pos (+ snip-pos (string-length old)))
-                      (insert new snip-pos snip-pos #f)))
-                  (loop prev-snip)))))))
-    
+                      (set! changes-to-make
+                            (cons (λ () (insert new snip-pos snip-pos #f))
+                                  changes-to-make))))
+                  (loop prev-snip))))
+            (for ([change (in-list changes-to-make)])
+              (change)))))
+
       (super-new))))

gui-test/framework/tests/text.rkt

@@ -265,7 +265,32 @@
     (preferences:set 'framework:do-paste-normalization #t)
     (define t (new (text:normalize-paste-mixin text:basic%)))
     (send t as-a-paste (λ () (send t insert "x² x²\nx² x²\nx² x²\nx² x²\n")))
-    (check-equal? (send t get-text) "x2 x2\nx2 x2\nx2 x2\nx2 x2\n")))
+    (check-equal? (send t get-text) "x2 x2\nx2 x2\nx2 x2\nx2 x2\n"))
+
+  (let ()
+    (preferences:set 'framework:do-paste-normalization #t)
+    (define t (new (text:normalize-paste-mixin text:basic%)))
+    (send t as-a-paste (λ ()
+                         (send t insert "x²\n")
+                         (send t insert "x²\n")))
+    (check-equal? (send t get-text) "x2\nx2\n"))
+
+  (let ()
+    (preferences:set 'framework:do-paste-normalization #t)
+    (define t (new (text:normalize-paste-mixin text:basic%)))
+    (send t as-a-paste (λ ()
+                         (send t insert "x²\n")
+                         (send t insert "x³\n")))
+    (check-equal? (send t get-text) "x2\nx3\n"))
+
+  (let ()
+    (preferences:set 'framework:do-paste-normalization #t)
+    (define t (new (text:normalize-paste-mixin text:basic%)))
+    (send t as-a-paste (λ ()
+                         (send t insert "x²\n")
+                         (send t insert "x³\n")
+                         (send t insert "x³\n")))
+    (check-equal? (send t get-text) "x2\nx3\nx3\n")))
 
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