Merge pull request #1427 from rkday/try_body

Allow multiple expressions in a try

NEWS

@@ -51,6 +51,7 @@ Changes from 0.13.0
      a for loop
    * `else` clauses in `for` and `while` are recognized more reliably
    * Argument destructuring no longer interferes with function docstrings.
+   * Multiple expressions are now allowed in `try`
 
    [ Misc. Improvements ]
    * `read`, `read_str`, and `eval` are exposed and documented as top-level

docs/language/api.rst

@@ -1666,6 +1666,7 @@ actions (``finally``).
 
     (try
       (error-prone-function)
+      (another-error-prone-function)
       (except [ZeroDivisionError]
         (print "Division by zero"))
       (except [[IndexError KeyboardInterrupt]]
@@ -1679,13 +1680,13 @@ actions (``finally``).
       (finally
         (print "All done")))
 
-The first argument of ``try`` is its body. (To put more than one form in the
-body, use ``do``.) Then comes any number of ``except`` clauses, then optionally
-an ``else`` clause, then optionally a ``finally`` clause. If an exception is
-raised with a matching ``except`` clause during the execution of the body, that
-``except`` clause will be executed. If no exceptions are raised, the ``else``
-clause is executed. The ``finally`` clause will be executed last regardless of
-whether an exception was raised.
+The first argument of ``try`` is its body, which can contain one or more forms.
+Then comes any number of ``except`` clauses, then optionally an ``else``
+clause, then optionally a ``finally`` clause. If an exception is raised with a
+matching ``except`` clause during the execution of the body, that ``except``
+clause will be executed. If no exceptions are raised, the ``else`` clause is
+executed. The ``finally`` clause will be executed last regardless of whether an
+exception was raised.
 
 The return value of ``try`` is the last form of the ``except`` clause that was
 run, or the last form of ``else`` if no exception was raised, or the ``try``

hy/compiler.py

@@ -843,8 +843,14 @@ class HyASTCompiler(object):
         expr = copy.deepcopy(expr)
         expr.pop(0)  # try
 
-        # (try something…)
-        body = self.compile(expr.pop(0) if expr else [])
+        # (try something somethingelse…)
+        body = Result()
+        # Check against HyExpression and HySymbol to avoid incorrectly
+        # matching [except ...] or ("except" ...)
+        while expr and not (isinstance(expr[0], HyExpression)
+                            and isinstance(expr[0][0], HySymbol)
+                            and expr[0][0] in ("except", "else", "finally")):
+            body += self.compile(expr.pop(0))
 
         var = self.get_anon_var()
         name = asty.Name(expr, id=ast_str(var), ctx=ast.Store())

tests/native_tests/language.hy

@@ -515,10 +515,16 @@
 
   (try (do) (except [IOError]) (except))
 
+  ; test that multiple expressions in a try get evaluated
+  (setv value 0)
+  (try (+= value 1) (+= value 2)  (except [IOError]) (except))
+  (assert (= value 3))
+
   ;; Test correct (raise)
   (setv passed False)
   (try
    (try
+    (do)
     (raise IndexError)
     (except [IndexError] (raise)))
    (except [IndexError]
@@ -650,7 +656,25 @@
       (setv x 45))
     (else (setv x 44)))
    (except))
-  (assert (= x 0)))
+  (assert (= x 0))
+
+  ; test that [except ...] and ("except" ...) aren't treated like (except ...),
+  ; and that the code there is evaluated normally
+  (setv x 0)
+  (try
+    (+= x 1)
+    ("except" [IOError]  (+= x 1))
+    (except))
+
+  (assert (= x 2))
+
+  (setv x 0)
+  (try
+    (+= x 1)
+    [except [IOError]  (+= x 1)]
+    (except))
+
+  (assert (= x 2)))
 
 (defn test-earmuffs []
   "NATIVE: Test earmuffs"