Assert now may take an optional label, like in Python

docs/language/api.rst

@@ -163,15 +163,23 @@ other case, the first false value will be returned. Example usage:
 assert
 ------
 
-``assert`` is used to verify conditions while the program is running. If the
-condition is not met, an ``AssertionError`` is raised. Example usage:
+``assert`` is used to verify conditions while the program is
+running. If the condition is not met, an :exc:`AssertionError` is
+raised. ``assert`` may take one or two parameters.  The first
+parameter is the condition to check, and it should evaluate to either
+``True`` or ``False``. The second parameter, optional, is a label for
+the assert, and is the string that will be raised with the
+:exc:`AssertionError`. For example:
 
 .. code-block:: clj
 
-    (assert (= variable expected-value))
+  (assert (= variable expected-value))
 
-``assert`` takes a single parameter, a conditional that evaluates to either
-``True`` or ``False``.
+  (assert False)
+  ; AssertionError
+
+  (assert (= 1 2) "one should equal two")
+  ; AssertionError: one should equal two
 
 
 assoc

hy/compiler.py

@@ -1028,13 +1028,17 @@ class HyASTCompiler(object):
         return ret
 
     @builds("assert")
-    @checkargs(1)
+    @checkargs(min=1, max=2)
     def compile_assert_expression(self, expr):
         expr.pop(0)  # assert
         e = expr.pop(0)
+        if len(expr) == 1:
+            msg = self.compile(expr.pop(0)).force_expr
+        else:
+            msg = None
         ret = self.compile(e)
         ret += ast.Assert(test=ret.force_expr,
-                          msg=None,
+                          msg=msg,
                           lineno=e.start_line,
                           col_offset=e.start_column)
 

tests/compilers/test_ast.py

@@ -198,14 +198,21 @@ def test_ast_bad_except():
 
 
 def test_ast_good_assert():
-    "Make sure AST can compile valid assert"
+    """Make sure AST can compile valid asserts. Asserts may or may not
+    include a label."""
     can_compile("(assert 1)")
+    can_compile("(assert 1 \"Assert label\")")
+    can_compile("(assert 1 (+ \"spam \" \"eggs\"))")
+    can_compile("(assert 1 12345)")
+    can_compile("(assert 1 nil)")
+    can_compile("(assert 1 (+ 2 \"incoming eggsception\"))")
 
 
 def test_ast_bad_assert():
     "Make sure AST can't compile invalid assert"
     cant_compile("(assert)")
-    cant_compile("(assert 1 2)")
+    cant_compile("(assert 1 2 3)")
+    cant_compile("(assert 1 [1 2] 3)")
 
 
 def test_ast_good_global():