Make try / except work

Issue: skulpt#38 on Github Issue: 109 and 114 on Google Code I did this by not generating a JavaScript try block, but instead added a try/catch around the whole run-time switch loop. Each Python try/except already did a push/pop of the except block on the $exc stack. So if the outer JS try/catch is triggered, it checks the exception block stack and jumps to the exception block. If there is no active exception, it means some other runtime error has occurred so the JS rethrows the exception so it is exposed to the user in the browser. This approach makes it far easier to implement the full try/except/else/finally as any nesting issues are no longer a problem - I did not implement that in this fix - but note that it is now easier if someone wants to do it. I am sure this code could be improved by someone more intimate with the runtime. *** This change may need to be adjusted for all the other instances of switchCode and suffixCode in src/compile.js Not knowing how to test those other cases I left them alone. At least the changes to setupExcept and endExcept will insure that the generated JS will be syntactically correct. The worst that will happen is that when code in a try block blows up, we will not know to run the except block. The other problem is that we might catch something that is really an internal error - it might be nice to add code in the above catch block that looked at the kind of exception and only popped the stack for exceptions that are from the original code rather than artifacts of some code generation or execution environment error. We at least err on the side of exceptions being revealed to the user. I added comments to these effects in the code - you may want to remove those when you do the pull / merge of the changes. I just wanted to leave a really clear trail.
Duncanr-glitch · Jan 24, 2013 · fbeb06e · fbeb06e
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diff --git a/test/run/t335.py b/test/run/t335.py
@@ -0,0 +1,105 @@
+print "----Start 01"
+try:
+    print "First try"
+    try:
+        print "Second try - should see Second except next"
+        i = int('badint');
+        print "Second try - should not see this"
+    except:
+        print "Second except"
+    print "First try - should see First except next"
+    i = float('otherbadint')
+    print "First try - should not see this"
+except:
+    print "First except"
+print "----End 01"
+
+print "----Start 02"
+try:
+    print "First try"
+    try:
+        print "Second try"
+    except:
+        print "Second except - should not see this"
+    print "First try - should see First except next"
+    i = float('otherbadint')
+    print "First try - should not see this"
+except:
+    print "First except"
+print "----End 02"
+
+print "----Start 03"
+try:
+    print "First try"
+    try:
+        print "Second try"
+    except:
+        print "Second except - should not see this"
+    print "First try - after inner try"
+except:
+    print "First except - should not see this"
+print "----End 03"
+
+print "----Start 04"
+try:
+    print "First try - shuold see First Except next"
+    i = int('first');
+    print "First try - should not see this"
+except:
+    print "First except"
+    try:
+        print "Second try - should see Second except next"
+        i = int('badint');
+        print "Second try - should not see this"
+    except:
+        print "Second except"
+    print "First except - After inner try/except"
+print "----End 04"
+
+print "----Start 05"
+try:
+    print "First try"
+    try:
+        print "Second try - should see Second except next"
+        i = int('badint');
+        print "Second try - should not see this"
+    except:
+        print "Second except - should see First except next"
+        i = float('otherbadint')
+        print "Second except - should not see this"
+    print "First try - should not see this"
+except:
+    print "First except"
+print "----End 05"
+
+print "----Start 06"
+try:
+    print "First try"
+    if 123 < 12345 :
+        if 456 < 4567 :
+            print "You should see this"
+        else:
+            print "You should not see this (inner)"
+    else:
+        print "You should not see this"
+    print "First try - near the end"
+except:
+    print "First except - should not see this"
+print "----End 06"
+
+print "----Start 07"
+try:
+    print "First try"
+    if 123 < 12345 :
+        if 456 < 4567 :
+            print "Next you should see First except"
+            i = int('badint')
+        else:
+            print "You should not see this (inner)"
+    else:
+        print "You should not see this"
+    print "First try - near the end - you should not see this"
+except:
+    print "First except - should see this"
+print "----End 07"
+
diff --git a/test/run/t335.py.real b/test/run/t335.py.real
@@ -0,0 +1,41 @@
+----Start 01
+First try
+Second try - should see Second except next
+Second except
+First try - should see First except next
+First except
+----End 01
+----Start 02
+First try
+Second try
+First try - should see First except next
+First except
+----End 02
+----Start 03
+First try
+Second try
+First try - after inner try
+----End 03
+----Start 04
+First try - shuold see First Except next
+First except
+Second try - should see Second except next
+Second except
+First except - After inner try/except
+----End 04
+----Start 05
+First try
+Second try - should see Second except next
+Second except - should see First except next
+First except
+----End 05
+----Start 06
+First try
+You should see this
+First try - near the end
+----End 06
+----Start 07
+First try
+Next you should see First except
+First except - should see this
+----End 07
diff --git a/test/run/t335.py.symtab b/test/run/t335.py.symtab
@@ -0,0 +1,42 @@
+Sym_type: module
+Sym_name: top
+Sym_lineno: 0
+Sym_nested: False
+Sym_haschildren: False
+-- Identifiers --
+name: float
+  is_referenced: True
+  is_imported: False
+  is_parameter: False
+  is_global: True
+  is_declared_global: False
+  is_local: False
+  is_free: False
+  is_assigned: False
+  is_namespace: False
+  namespaces: [
+  ]
+name: i
+  is_referenced: False
+  is_imported: False
+  is_parameter: False
+  is_global: False
+  is_declared_global: False
+  is_local: True
+  is_free: False
+  is_assigned: True
+  is_namespace: False
+  namespaces: [
+  ]
+name: int
+  is_referenced: True
+  is_imported: False
+  is_parameter: False
+  is_global: True
+  is_declared_global: False
+  is_local: False
+  is_free: False
+  is_assigned: False
+  is_namespace: False
+  namespaces: [
+  ]