Better catch syntax

The syntax is now changed to:

  (catch [] BODY)
  (catch [Exception] BODY)
  (catch [e Exception] BODY)
  (catch [e [Exception1 Exception2]] BODY)

Signed-off-by: Julien Danjou <julien@danjou.info>

hy/compiler.py

@@ -1,4 +1,7 @@
+# -*- encoding: utf-8 -*-
+#
 # Copyright (c) 2013 Paul Tagliamonte <paultag@debian.org>
+# Copyright (c) 2013 Julien Danjou <julien@danjou.info>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a
 # copy of this software and associated documentation files (the "Software"),
@@ -191,12 +194,30 @@ class HyASTCompiler(object):
             orelse=[])
 
     @builds("catch")
-    @checkargs(min=2)
     def compile_catch_expression(self, expr):
         expr.pop(0)  # catch
-        _type = self.compile(expr.pop(0))
-        name = expr.pop(0)
 
+        try:
+            exceptions = expr.pop(0)
+        except IndexError:
+            exceptions = []
+        # exceptions catch should be either:
+        # [[list of exceptions]]
+        # or
+        # [variable [list of exceptions]]
+        # or
+        # [variable exception]
+        # or
+        # [exception]
+        # or
+        # []
+        if len(exceptions) > 2:
+            raise TypeError("`catch' exceptions list is too long")
+
+        # [variable [list of exceptions]]
+        # let's pop variable and use it as name
+        if len(exceptions) == 2:
+            name = exceptions.pop(0)
             if sys.version_info[0] >= 3:
                 # Python3 features a change where the Exception handler
                 # moved the name from a Name() to a pure Python String type.
@@ -207,13 +228,43 @@ class HyASTCompiler(object):
             else:
                 # Python2 requires an ast.Name, set to ctx Store.
                 name = self._storeize(self.compile(name))
+        else:
+            name = None
+
+        try:
+            exceptions_list = exceptions.pop(0)
+        except IndexError:
+            exceptions_list = []
+
+        if isinstance(exceptions_list, list):
+            if len(exceptions_list):
+                # [FooBar BarFoo] → catch Foobar and BarFoo exceptions
+                _type = ast.Tuple(elts=[self.compile(x)
+                                        for x in exceptions_list],
+                                  lineno=expr.start_line,
+                                  col_offset=expr.start_column,
+                                  ctx=ast.Load())
+            else:
+                # [] → all exceptions catched
+                _type = None
+        elif isinstance(exceptions_list, HySymbol):
+            _type = self.compile(exceptions_list)
+        else:
+            raise TypeError("`catch' needs a valid exception list to catch")
+
+        if len(expr) == 0:
+            # No body
+            body = [ast.Pass(lineno=expr.start_line,
+                             col_offset=expr.start_column)]
+        else:
+            body = self._code_branch([self.compile(x) for x in expr])
 
         return ast.ExceptHandler(
             lineno=expr.start_line,
             col_offset=expr.start_column,
             type=_type,
             name=name,
-            body=self._code_branch([self.compile(x) for x in expr]))
+            body=body)
 
     def _code_branch(self, branch):
         if isinstance(branch, list):

tests/compilers/test_ast.py

@@ -116,13 +116,20 @@ def test_ast_bad_try():
 
 def test_ast_good_catch():
     "Make sure AST can compile valid catch"
-    hy_compile(tokenize("(catch 1 2)"))
+    hy_compile(tokenize("(catch)"))
+    hy_compile(tokenize("(catch [])"))
+    hy_compile(tokenize("(catch [Foobar])"))
+    # hy_compile(tokenize("(catch [[]])"))
+    # hy_compile(tokenize("(catch [x FooBar])"))
+    # hy_compile(tokenize("(catch [x [FooBar BarFoo]])"))
+    # hy_compile(tokenize("(catch [x [FooBar BarFoo]])"))
 
 
 def test_ast_bad_catch():
     "Make sure AST can't compile invalid catch"
-    cant_compile("(catch)")
     cant_compile("(catch 1)")
+    cant_compile("(catch [1 3])")
+    cant_compile("(catch [x [FooBar] BarBar]])")
 
 
 def test_ast_good_assert():

tests/native_tests/language.hy

@@ -164,8 +164,56 @@
   "NATIVE: test Exceptions"
   (try
     (throw (KeyError))
-  (catch IOError  e (assert (= 2 1)))
-  (catch KeyError e (+ 1 1) (assert (= 1 1)))))
+    (catch [[IOError]] (assert false))
+    (catch [e [KeyError]] (assert e)))
+
+  (try
+    (get [1] 3)
+    (catch [IndexError] (assert true))
+    (catch [IndexError] (pass)))
+
+  (try
+    (print foobar42ofthebaz)
+    (catch [IndexError] (assert false))
+    (catch [NameError] (pass)))
+
+  (try
+    (get [1] 3)
+    (catch [e IndexError] (assert (isinstance e IndexError))))
+
+  (try
+    (get [1] 3)
+    (catch [e [IndexError NameError]] (assert (isinstance e IndexError))))
+
+  (try
+    (print foobar42ofthebaz)
+    (catch [e [IndexError NameError]] (assert (isinstance e NameError))))
+
+  (try
+    (print foobar42)
+    (catch [[IndexError NameError]] (pass)))
+
+  (try
+    (get [1] 3)
+    (catch [[IndexError NameError]] (pass)))
+
+  (try
+    (print foobar42ofthebaz)
+    (catch))
+
+  (try
+    (print foobar42ofthebaz)
+    (catch []))
+
+  (try
+    (print foobar42ofthebaz)
+    (catch [] (pass)))
+
+  (try
+    (print foobar42ofthebaz)
+    (catch []
+        (setv foobar42ofthebaz 42)
+        (assert (= foobar42ofthebaz 42)))))
 
 (defn test-earmuffs []
   "NATIVE: Test earmuffs"
@@ -327,7 +375,7 @@
              6))
   (try
     (assert (= x 42))                   ; This ain't true
-    (catch NameError e (assert e)))
+    (catch [e [NameError]] (assert e)))
   (assert (= y 123)))