unify TryExcept and TryFinally (closes #12199)

Include/Python-ast.h

@@ -66,10 +66,9 @@ struct _mod {
 enum _stmt_kind {FunctionDef_kind=1, ClassDef_kind=2, Return_kind=3,
                   Delete_kind=4, Assign_kind=5, AugAssign_kind=6, For_kind=7,
                   While_kind=8, If_kind=9, With_kind=10, Raise_kind=11,
-                  TryExcept_kind=12, TryFinally_kind=13, Assert_kind=14,
-                  Import_kind=15, ImportFrom_kind=16, Global_kind=17,
-                  Nonlocal_kind=18, Expr_kind=19, Pass_kind=20, Break_kind=21,
-                  Continue_kind=22};
+                  Try_kind=12, Assert_kind=13, Import_kind=14,
+                  ImportFrom_kind=15, Global_kind=16, Nonlocal_kind=17,
+                  Expr_kind=18, Pass_kind=19, Break_kind=20, Continue_kind=21};
 struct _stmt {
         enum _stmt_kind kind;
         union {
@@ -143,12 +142,8 @@ struct _stmt {
                         asdl_seq *body;
                         asdl_seq *handlers;
                         asdl_seq *orelse;
-                } TryExcept;
-                
-                struct {
-                        asdl_seq *body;
                         asdl_seq *finalbody;
-                } TryFinally;
+                } Try;
                 
                 struct {
                         expr_ty test;
@@ -433,12 +428,10 @@ stmt_ty _Py_With(asdl_seq * items, asdl_seq * body, int lineno, int col_offset,
 #define Raise(a0, a1, a2, a3, a4) _Py_Raise(a0, a1, a2, a3, a4)
 stmt_ty _Py_Raise(expr_ty exc, expr_ty cause, int lineno, int col_offset,
                   PyArena *arena);
-#define TryExcept(a0, a1, a2, a3, a4, a5) _Py_TryExcept(a0, a1, a2, a3, a4, a5)
-stmt_ty _Py_TryExcept(asdl_seq * body, asdl_seq * handlers, asdl_seq * orelse,
-                      int lineno, int col_offset, PyArena *arena);
-#define TryFinally(a0, a1, a2, a3, a4) _Py_TryFinally(a0, a1, a2, a3, a4)
-stmt_ty _Py_TryFinally(asdl_seq * body, asdl_seq * finalbody, int lineno, int
-                       col_offset, PyArena *arena);
+#define Try(a0, a1, a2, a3, a4, a5, a6) _Py_Try(a0, a1, a2, a3, a4, a5, a6)
+stmt_ty _Py_Try(asdl_seq * body, asdl_seq * handlers, asdl_seq * orelse,
+                asdl_seq * finalbody, int lineno, int col_offset, PyArena
+                *arena);
 #define Assert(a0, a1, a2, a3, a4) _Py_Assert(a0, a1, a2, a3, a4)
 stmt_ty _Py_Assert(expr_ty test, expr_ty msg, int lineno, int col_offset,
                    PyArena *arena);

Lib/test/test_ast.py

@@ -347,8 +347,8 @@ exec_results = [
 ('Module', [('With', (1, 0), [('withitem', ('Name', (1, 5), 'x', ('Load',)), ('Name', (1, 10), 'y', ('Store',)))], [('Pass', (1, 13))])]),
 ('Module', [('With', (1, 0), [('withitem', ('Name', (1, 5), 'x', ('Load',)), ('Name', (1, 10), 'y', ('Store',))), ('withitem', ('Name', (1, 13), 'z', ('Load',)), ('Name', (1, 18), 'q', ('Store',)))], [('Pass', (1, 21))])]),
 ('Module', [('Raise', (1, 0), ('Call', (1, 6), ('Name', (1, 6), 'Exception', ('Load',)), [('Str', (1, 16), 'string')], [], None, None), None)]),
-('Module', [('TryExcept', (1, 0), [('Pass', (2, 2))], [('ExceptHandler', (3, 0), ('Name', (3, 7), 'Exception', ('Load',)), None, [('Pass', (4, 2))])], [])]),
-('Module', [('TryFinally', (1, 0), [('Pass', (2, 2))], [('Pass', (4, 2))])]),
+('Module', [('Try', (1, 0), [('Pass', (2, 2))], [('ExceptHandler', (3, 0), ('Name', (3, 7), 'Exception', ('Load',)), None, [('Pass', (4, 2))])], [], [])]),
+('Module', [('Try', (1, 0), [('Pass', (2, 2))], [], [], [('Pass', (4, 2))])]),
 ('Module', [('Assert', (1, 0), ('Name', (1, 7), 'v', ('Load',)), None)]),
 ('Module', [('Import', (1, 0), [('alias', 'sys', None)])]),
 ('Module', [('ImportFrom', (1, 0), 'sys', [('alias', 'v', None)], 0)]),

Misc/NEWS

@@ -10,6 +10,9 @@ What's New in Python 3.3 Alpha 1?
 Core and Builtins
 -----------------
 
+- Issue #12199: The TryExcept and TryFinally and AST nodes have been unified
+  into a Try node.
+
 - Issue #9670: Increase the default stack size for secondary threads on
   Mac OS X and FreeBSD to reduce the chances of a crash instead of a
   "maximum recursion depth" RuntimeError exception.

Parser/Python.asdl

@@ -31,8 +31,7 @@ module Python
 	      | With(withitem* items, stmt* body)
 
 	      | Raise(expr? exc, expr? cause)
-	      | TryExcept(stmt* body, excepthandler* handlers, stmt* orelse)
-	      | TryFinally(stmt* body, stmt* finalbody)
+	      | Try(stmt* body, excepthandler* handlers, stmt* orelse, stmt* finalbody)
 	      | Assert(expr test, expr? msg)
 
 	      | Import(alias* names)

Python/ast.c

@@ -2893,7 +2893,7 @@ ast_for_try_stmt(struct compiling *c, const node *n)
 {
     const int nch = NCH(n);
     int n_except = (nch - 3)/3;
-    asdl_seq *body, *orelse = NULL, *finally = NULL;
+    asdl_seq *body, *handlers = NULL, *orelse = NULL, *finally = NULL;
 
     REQ(n, try_stmt);
 
@@ -2934,9 +2934,8 @@ ast_for_try_stmt(struct compiling *c, const node *n)
 
     if (n_except > 0) {
         int i;
-        stmt_ty except_st;
         /* process except statements to create a try ... except */
-        asdl_seq *handlers = asdl_seq_new(n_except, c->c_arena);
+        handlers = asdl_seq_new(n_except, c->c_arena);
         if (handlers == NULL)
             return NULL;
 
@@ -2947,23 +2946,10 @@ ast_for_try_stmt(struct compiling *c, const node *n)
                 return NULL;
             asdl_seq_SET(handlers, i, e);
         }
-
-        except_st = TryExcept(body, handlers, orelse, LINENO(n),
-                              n->n_col_offset, c->c_arena);
-        if (!finally)
-            return except_st;
-
-        /* if a 'finally' is present too, we nest the TryExcept within a
-           TryFinally to emulate try ... except ... finally */
-        body = asdl_seq_new(1, c->c_arena);
-        if (body == NULL)
-            return NULL;
-        asdl_seq_SET(body, 0, except_st);
     }
 
-    /* must be a try ... finally (except clauses are in body, if any exist) */
-    assert(finally != NULL);
-    return TryFinally(body, finally, LINENO(n), n->n_col_offset, c->c_arena);
+    assert(finally != NULL || asdl_seq_LEN(handlers));
+    return Try(body, handlers, orelse, finally, LINENO(n), n->n_col_offset, c->c_arena);
 }
 
 /* with_item: test ['as' expr] */

Python/compile.c

@@ -185,6 +185,7 @@ static int compiler_call_helper(struct compiler *c, int n,
                                 asdl_seq *keywords,
                                 expr_ty starargs,
                                 expr_ty kwargs);
+static int compiler_try_except(struct compiler *, stmt_ty);
 
 static PyCodeObject *assemble(struct compiler *, int addNone);
 static PyObject *__doc__;
@@ -1898,7 +1899,13 @@ compiler_try_finally(struct compiler *c, stmt_ty s)
     compiler_use_next_block(c, body);
     if (!compiler_push_fblock(c, FINALLY_TRY, body))
         return 0;
-    VISIT_SEQ(c, stmt, s->v.TryFinally.body);
+    if (s->v.Try.handlers && asdl_seq_LEN(s->v.Try.handlers)) {
+        if (!compiler_try_except(c, s))
+            return 0;
+    }
+    else {
+        VISIT_SEQ(c, stmt, s->v.Try.body);
+    }
     ADDOP(c, POP_BLOCK);
     compiler_pop_fblock(c, FINALLY_TRY, body);
 
@@ -1906,7 +1913,7 @@ compiler_try_finally(struct compiler *c, stmt_ty s)
     compiler_use_next_block(c, end);
     if (!compiler_push_fblock(c, FINALLY_END, end))
         return 0;
-    VISIT_SEQ(c, stmt, s->v.TryFinally.finalbody);
+    VISIT_SEQ(c, stmt, s->v.Try.finalbody);
     ADDOP(c, END_FINALLY);
     compiler_pop_fblock(c, FINALLY_END, end);
 
@@ -1960,15 +1967,15 @@ compiler_try_except(struct compiler *c, stmt_ty s)
     compiler_use_next_block(c, body);
     if (!compiler_push_fblock(c, EXCEPT, body))
         return 0;
-    VISIT_SEQ(c, stmt, s->v.TryExcept.body);
+    VISIT_SEQ(c, stmt, s->v.Try.body);
     ADDOP(c, POP_BLOCK);
     compiler_pop_fblock(c, EXCEPT, body);
     ADDOP_JREL(c, JUMP_FORWARD, orelse);
-    n = asdl_seq_LEN(s->v.TryExcept.handlers);
+    n = asdl_seq_LEN(s->v.Try.handlers);
     compiler_use_next_block(c, except);
     for (i = 0; i < n; i++) {
         excepthandler_ty handler = (excepthandler_ty)asdl_seq_GET(
-            s->v.TryExcept.handlers, i);
+            s->v.Try.handlers, i);
         if (!handler->v.ExceptHandler.type && i < n-1)
             return compiler_error(c, "default 'except:' must be last");
         c->u->u_lineno_set = 0;
@@ -2055,11 +2062,20 @@ compiler_try_except(struct compiler *c, stmt_ty s)
     }
     ADDOP(c, END_FINALLY);
     compiler_use_next_block(c, orelse);
-    VISIT_SEQ(c, stmt, s->v.TryExcept.orelse);
+    VISIT_SEQ(c, stmt, s->v.Try.orelse);
     compiler_use_next_block(c, end);
     return 1;
 }
 
+static int
+compiler_try(struct compiler *c, stmt_ty s) {
+    if (s->v.Try.finalbody && asdl_seq_LEN(s->v.Try.finalbody))
+        return compiler_try_finally(c, s);
+    else
+        return compiler_try_except(c, s);
+}
+
+
 static int
 compiler_import_as(struct compiler *c, identifier name, identifier asname)
 {
@@ -2307,10 +2323,8 @@ compiler_visit_stmt(struct compiler *c, stmt_ty s)
         }
         ADDOP_I(c, RAISE_VARARGS, n);
         break;
-    case TryExcept_kind:
-        return compiler_try_except(c, s);
-    case TryFinally_kind:
-        return compiler_try_finally(c, s);
+    case Try_kind:
+        return compiler_try(c, s);
     case Assert_kind:
         return compiler_assert(c, s);
     case Import_kind:

Python/symtable.c

@@ -1211,14 +1211,11 @@ symtable_visit_stmt(struct symtable *st, stmt_ty s)
             }
         }
         break;
-    case TryExcept_kind:
-        VISIT_SEQ(st, stmt, s->v.TryExcept.body);
-        VISIT_SEQ(st, stmt, s->v.TryExcept.orelse);
-        VISIT_SEQ(st, excepthandler, s->v.TryExcept.handlers);
-        break;
-    case TryFinally_kind:
-        VISIT_SEQ(st, stmt, s->v.TryFinally.body);
-        VISIT_SEQ(st, stmt, s->v.TryFinally.finalbody);
+    case Try_kind:
+        VISIT_SEQ(st, stmt, s->v.Try.body);
+        VISIT_SEQ(st, stmt, s->v.Try.orelse);
+        VISIT_SEQ(st, excepthandler, s->v.Try.handlers);
+        VISIT_SEQ(st, stmt, s->v.Try.finalbody);
         break;
     case Assert_kind:
         VISIT(st, expr, s->v.Assert.test);