Add environment code satisfying unit test

cibuildwheel/environment.py

@@ -0,0 +1,73 @@
+import bashlex
+from . import bashlex_eval
+
+
+class EnvironmentParseError(Exception):
+    pass
+
+
+def parse_environment(env_string):
+    env_items = split_env_items(env_string)
+    assignments = [EnvironmentAssignment(item) for item in env_items]
+    return ParsedEnvironment(assignments=assignments)
+
+
+def split_env_items(env_string):
+    '''Splits space-separated variable assignments into a list of individual assignments.
+
+    >>> split_env_items('VAR=abc')
+    ['VAR=abc']
+    >>> split_env_items('VAR="a string" THING=3')
+    ['VAR="a string"', 'THING=3']
+    >>> split_env_items('VAR="a string" THING=\\'single "quotes"\\'')
+    ['VAR="a string"', 'THING=\\'single "quotes"\\'']
+    >>> split_env_items('VAR="dont \\\\"forget\\\\" about backslashes"')
+    ['VAR="dont \\\\"forget\\\\" about backslashes"']
+    '''
+    return list(bashlex.split(env_string))
+
+
+class EnvironmentAssignment(object):
+    def __init__(self, assignment):
+        name, equals, value = assignment.partition('=')
+        if not equals:
+            raise EnvironmentParseError(assignment)
+        self.name = name
+        self.value = value
+
+        if value:
+            command_node = bashlex.parsesingle(value)
+
+            if len(command_node.parts) != 1:
+                raise ValueError('"%s" has too many parts' % value)
+
+            self.value_word_node = command_node.parts[0]
+        else:
+            self.value_word_node = None
+
+    def evaluated_value(self, environment):
+        '''Returns the value of this assignment, as evaluated in the environment'''
+        if self.value_word_node:
+            return bashlex_eval.evaluate_node(self.value_word_node, environment=environment)
+        else:
+            return ''
+
+    def as_shell_assignment(self):
+        return 'export %s=%s' % (self.name, self.value)
+
+
+class ParsedEnvironment(object):
+    def __init__(self, assignments):
+        self.assignments = assignments
+
+    def as_dictionary(self, prev_environment):
+        environment = prev_environment.copy()
+
+        for assignment in self.assignments:
+            value = assignment.evaluated_value(environment=environment)
+            environment[assignment.name] = value
+
+        return environment
+
+    def as_shell_commands(self):
+        return [a.as_shell_assignment() for a in self.assignments]