Add the Sass 3.4 *-exists functions. Fixes #226, #229, #353

6 files changed, 116 insertions, 13 deletions

diff --git a/scss/ast.py b/scss/ast.py
index a8ab69b..122fbf2 100644
--- a/scss/ast.py
+++ b/scss/ast.py
@@ -212,10 +212,6 @@ class CallOp(Expression):
         funct = None
         try:
             funct = calculator.namespace.function(func_name, argspec_len)
-            # @functions take a ns as first arg.  TODO: Python functions possibly
-            # should too
-            if getattr(funct, '__name__', None) == '__call':
-                funct = partial(funct, calculator.namespace)
         except KeyError:
             try:
                 # DEVIATION: Fall back to single parameter
@@ -226,7 +222,12 @@ class CallOp(Expression):
                     log.error("Function not found: %s:%s", func_name, argspec_len, extra={'stack': True})
 
         if funct:
-            ret = funct(*args, **kwargs)
+            if getattr(funct, '_pyscss_needs_namespace', False):
+                # @functions and some Python functions take the namespace as an
+                # extra first argument
+                ret = funct(calculator.namespace, *args, **kwargs)
+            else:
+                ret = funct(*args, **kwargs)
             if not isinstance(ret, Value):
                 raise TypeError("Expected Sass type as return value, got %r" % (ret,))
             return ret
diff --git a/scss/compiler.py b/scss/compiler.py
index e0ca8d5..08c5638 100644
--- a/scss/compiler.py
+++ b/scss/compiler.py
@@ -684,6 +684,7 @@ class Compilation(object):
                         return e.retval
                     else:
                         return Null()
+                __call._pyscss_needs_namespace = True
                 return __call
             _mixin = _call(mixin)
             _mixin.mixin = mixin
diff --git a/scss/extension/core.py b/scss/extension/core.py
index 7967429..b939d1c 100644
--- a/scss/extension/core.py
+++ b/scss/extension/core.py
@@ -840,8 +840,71 @@ def map_merge_deep(*maps):
     return Map(pairs)
 
 
+@ns.declare
+def keywords(value):
+    """Extract named arguments, as a map, from an argument list."""
+    expect_type(value, Arglist)
+    return value.extract_keywords()
+
+
 # ------------------------------------------------------------------------------
-# Meta functions
+# Introspection functions
+
+# TODO feature-exists
+
+@ns.declare_internal
+def variable_exists(namespace, name):
+    expect_type(name, String)
+    try:
+        namespace.variable('$' + name.value)
+    except KeyError:
+        return Boolean(False)
+    else:
+        return Boolean(True)
+
+
+@ns.declare_internal
+def global_variable_exists(namespace, name):
+    expect_type(name, String)
+
+    # TODO this is...  imperfect and invasive, but should be a good
+    # approximation
+    scope = namespace._variables
+    while len(scope.maps) > 1:
+        scope = scope.maps[-1]
+
+    try:
+        scope['$' + name.value]
+    except KeyError:
+        return Boolean(False)
+    else:
+        return Boolean(True)
+
+
+@ns.declare_internal
+def function_exists(namespace, name):
+    expect_type(name, String)
+    # TODO invasive, but there's no other way to ask for this at the moment
+    for fname, arity in namespace._functions.keys():
+        if name.value == fname:
+            return Boolean(True)
+    return Boolean(False)
+
+
+@ns.declare_internal
+def mixin_exists(namespace, name):
+    expect_type(name, String)
+    # TODO invasive, but there's no other way to ask for this at the moment
+    for fname, arity in namespace._mixins.keys():
+        if name.value == fname:
+            return Boolean(True)
+    return Boolean(False)
+
+
+@ns.declare
+def inspect(value):
+    return String.unquoted(value.render())
+
 
 @ns.declare
 def type_of(obj):  # -> bool, number, string, color, list
@@ -877,11 +940,7 @@ def comparable(number1, number2):
         and left.unit_denom == right.unit_denom)
 
 
-@ns.declare
-def keywords(value):
-    """Extract named arguments, as a map, from an argument list."""
-    expect_type(value, Arglist)
-    return value.extract_keywords()
+# TODO call
 
 
 # ------------------------------------------------------------------------------
diff --git a/scss/namespace.py b/scss/namespace.py
index 8076bca..939cde5 100644
--- a/scss/namespace.py
+++ b/scss/namespace.py
@@ -157,7 +157,17 @@ class Namespace(object):
 
         return decorator
 
-    def _auto_register_function(self, function, name):
+    def declare_internal(self, function):
+        """Like declare(), but the registered function will also receive the
+        current namespace as its first argument.  Useful for functions that
+        inspect the state of the compilation, like ``variable-exists()``.
+        Probably not so useful for anything else.
+        """
+        function._pyscss_needs_namespace = True
+        self._auto_register_function(function, function.__name__, 1)
+        return function
+
+    def _auto_register_function(self, function, name, ignore_args=0):
         name = name.replace('_', '-').rstrip('-')
         argspec = inspect.getargspec(function)
 
@@ -170,7 +180,7 @@ class Namespace(object):
                 num_optional = len(argspec.defaults)
             else:
                 num_optional = 0
-            num_args = len(argspec.args)
+            num_args = len(argspec.args) - ignore_args
             arities = range(num_args - num_optional, num_args + 1)
 
         for arity in arities:
diff --git a/scss/tests/files/general/global-variable-exists.css b/scss/tests/files/general/global-variable-exists.css
new file mode 100644
index 0000000..a614018
--- /dev/null
+++ b/scss/tests/files/general/global-variable-exists.css
@@ -0,0 +1,5 @@
+blockquote {
+  background: lime;
+  color: red;
+  float: right;
+}
diff --git a/scss/tests/files/general/global-variable-exists.scss b/scss/tests/files/general/global-variable-exists.scss
new file mode 100644
index 0000000..4404ed0
--- /dev/null
+++ b/scss/tests/files/general/global-variable-exists.scss
@@ -0,0 +1,27 @@
+@mixin myblockquote {
+  blockquote {
+    @if global-variable-exists(blockquote-color) {
+      background: $blockquote-color;
+    }
+    @else {
+      background: lime;
+    }
+
+    @if mixin-exists(myblockquote) {
+      color: red;
+    }
+    @else {
+      color: blue;
+    }
+
+    @if variable-exists(foo) {
+      float: left;
+    }
+    $foo: 1;
+    @if variable-exists(foo) {
+      float: right;
+    }
+  }
+}
+
+@include myblockquote;