jinja2/compiler.py

# -*- coding: utf-8 -*-
"""
    jinja2.compiler
    ~~~~~~~~~~~~~~~

    Compiles nodes into python code.

    :copyright: Copyright 2008 by Armin Ronacher.
    :license: GNU GPL.
"""
from copy import copy
from random import randrange
from cStringIO import StringIO
from jinja2 import nodes
from jinja2.visitor import NodeVisitor, NodeTransformer
from jinja2.exceptions import TemplateAssertionError


operators = {
    'eq':       '==',
    'ne':       '!=',
    'gt':       '>',
    'gteq':     '>=',
    'lt':       '<',
    'lteq':     '<=',
    'in':       'in',
    'notin':    'not in'
}


def generate(node, environment, filename, stream=None):
    is_child = node.find(nodes.Extends) is not None
    generator = CodeGenerator(environment, is_child, filename, stream)
    generator.visit(node)
    if stream is None:
        return generator.stream.getvalue()


class Identifiers(object):
    """Tracks the status of identifiers in frames."""

    def __init__(self):
        # variables that are known to be declared (probably from outer
        # frames or because they are special for the frame)
        self.declared = set()

        # names that are accessed without being explicitly declared by
        # this one or any of the outer scopes.  Names can appear both in
        # declared and undeclared.
        self.undeclared = set()

        # names that are declared locally
        self.declared_locally = set()

        # names that are declared by parameters
        self.declared_parameter = set()

        # filters that are declared locally
        self.declared_filter = set()
        self.undeclared_filter = dict()

    def add_special(self, name):
        """Register a special name like `loop`."""
        self.undeclared.discard(name)
        self.declared.add(name)

    def is_declared(self, name, local_only=False):
        """Check if a name is declared in this or an outer scope."""
        if name in self.declared_locally or name in self.declared_parameter:
            return True
        if local_only:
            return False
        return name in self.declared

    def find_shadowed(self):
        """Find all the shadowed names."""
        return self.declared & (self.declared_locally | self.declared_parameter)


class Frame(object):

    def __init__(self, parent=None):
        self.identifiers = Identifiers()
        self.toplevel = False
        self.parent = parent
        self.block = parent and parent.block or None
        if parent is not None:
            self.identifiers.declared.update(
                parent.identifiers.declared |
                parent.identifiers.declared_locally |
                parent.identifiers.declared_parameter
            )

    def copy(self):
        """Create a copy of the current one."""
        rv = copy(self)
        rv.identifiers = copy(self)
        return rv

    def inspect(self, nodes, hard_scope=False):
        """Walk the node and check for identifiers.  If the scope
        is hard (eg: enforce on a python level) overrides from outer
        scopes are tracked differently.
        """
        visitor = FrameIdentifierVisitor(self.identifiers, hard_scope)
        for node in nodes:
            visitor.visit(node)

    def inner(self):
        """Return an inner frame."""
        return Frame(self)


class FrameIdentifierVisitor(NodeVisitor):
    """A visitor for `Frame.inspect`."""

    def __init__(self, identifiers, hard_scope):
        self.identifiers = identifiers
        self.hard_scope = hard_scope

    def visit_Name(self, node):
        """All assignments to names go through this function."""
        if node.ctx in ('store', 'param'):
            self.identifiers.declared_locally.add(node.name)
        elif node.ctx == 'load':
            if not self.identifiers.is_declared(node.name, self.hard_scope):
                self.identifiers.undeclared.add(node.name)

    def visit_FilterCall(self, node):
        if not node.name in self.identifiers.declared_filter:
            uf = self.identifiers.undeclared_filter.get(node.name, 0) + 1
            if uf > 1:
                self.identifiers.declared_filter.add(node.name)
            self.identifiers.undeclared_filter[node.name] = uf

    def visit_Macro(self, node):
        """Macros set local."""
        self.identifiers.declared_locally.add(node.name)

    # stop traversing at instructions that have their own scope.
    visit_Block = visit_CallBlock = visit_FilterBlock = \
        visit_For = lambda s, n: None


class CodeGenerator(NodeVisitor):

    def __init__(self, environment, is_child, filename, stream=None):
        if stream is None:
            stream = StringIO()
        self.environment = environment
        self.is_child = is_child
        self.filename = filename
        self.stream = stream
        self.blocks = {}
        self.indentation = 0
        self.new_lines = 0
        self.last_identifier = 0
        self._last_line = 0
        self._first_write = True

    def temporary_identifier(self):
        self.last_identifier += 1
        return 't%d' % self.last_identifier

    def indent(self):
        self.indentation += 1

    def outdent(self, step=1):
        self.indentation -= step

    def blockvisit(self, nodes, frame, force_generator=False):
        self.indent()
        if force_generator:
            self.writeline('if 0: yield None')
        for node in nodes:
            self.visit(node, frame)
        self.outdent()

    def write(self, x):
        if self.new_lines:
            if not self._first_write:
                self.stream.write('\n' * self.new_lines)
            self._first_write = False
            self.stream.write('    ' * self.indentation)
            self.new_lines = 0
        self.stream.write(x)

    def writeline(self, x, node=None, extra=0):
        self.newline(node, extra)
        self.write(x)

    def newline(self, node=None, extra=0):
        self.new_lines = max(self.new_lines, 1 + extra)
        if node is not None and node.lineno != self._last_line:
            self.write('# line: %s' % node.lineno)
            self.new_lines = 1
            self._last_line = node.lineno

    def signature(self, node, frame, have_comma=True):
        have_comma = have_comma and [True] or []
        def touch_comma():
            if have_comma:
                self.write(', ')
            else:
                have_comma.append(True)

        for arg in node.args:
            touch_comma()
            self.visit(arg, frame)
        for kwarg in node.kwargs:
            touch_comma()
            self.visit(kwarg, frame)
        if node.dyn_args:
            touch_comma()
            self.visit(node.dyn_args, frame)
        if node.dyn_kwargs:
            touch_comma()
            self.visit(node.dyn_kwargs, frame)

    def pull_locals(self, frame, no_indent=False):
        if not no_indent:
            self.indent()
        for name in frame.identifiers.undeclared:
            self.writeline('l_%s = context[%r]' % (name, name))
        for name, count in frame.identifiers.undeclared_filter.iteritems():
            if count > 1:
                self.writeline('f_%s = context[%r]' % (name, name))
        if not no_indent:
            self.outdent()

    # -- Visitors

    def visit_Template(self, node, frame=None):
        assert frame is None, 'no root frame allowed'
        self.writeline('from jinja2.runtime import *')
        self.writeline('filename = %r' % self.filename)
        self.writeline('template_context = TemplateContext(global_context, '
                       'make_undefined, filename)')

        # generate the root render function.
        self.writeline('def root(context=template_context):', extra=1)
        self.indent()
        self.writeline('parent_root = None')
        self.outdent()
        frame = Frame()
        frame.inspect(node.body)
        frame.toplevel = True
        self.pull_locals(frame)
        self.blockvisit(node.body, frame, True)

        # make sure that the parent root is called.
        self.indent()
        self.writeline('if parent_root is not None:')
        self.indent()
        self.writeline('for event in parent_root(context):')
        self.indent()
        self.writeline('yield event')
        self.outdent(3)

        # at this point we now have the blocks collected and can visit them too.
        for name, block in self.blocks.iteritems():
            block_frame = Frame()
            block_frame.inspect(block.body)
            block_frame.block = name
            self.writeline('def block_%s(context):' % name, block, 1)
            self.pull_locals(block_frame)
            self.blockvisit(block.body, block_frame, True)

    def visit_Block(self, node, frame):
        """Call a block and register it for the template."""
        if node.name in self.blocks:
            raise TemplateAssertionError("the block '%s' was already defined" %
                                         node.name, node.lineno,
                                         self.filename)
        self.blocks[node.name] = node
        self.writeline('for event in block_%s(context):' % node.name)
        self.indent()
        self.writeline('yield event')
        self.outdent()

    def visit_Extends(self, node, frame):
        """Calls the extender."""
        if not frame.toplevel:
            raise TemplateAssertionError('cannot use extend from a non '
                                         'top-level scope', node.lineno,
                                         self.filename)
        self.writeline('if parent_root is not None:')
        self.indent()
        self.writeline('raise TemplateRuntimeError(%r)' %
                       'extended multiple times')
        self.outdent()
        self.writeline('parent_root = extends(', node, 1)
        self.visit(node.template, frame)
        self.write(', globals())')

    def visit_For(self, node, frame):
        loop_frame = frame.inner()
        loop_frame.inspect(node.iter_child_nodes())
        extended_loop = bool(node.else_) or \
                        'loop' in loop_frame.identifiers.undeclared
        loop_frame.identifiers.add_special('loop')

        # make sure we "backup" overridden, local identifiers
        # TODO: we should probably optimize this and check if the
        # identifier is in use afterwards.
        aliases = {}
        for name in loop_frame.identifiers.find_shadowed():
            aliases[name] = ident = self.temporary_identifier()
            self.writeline('%s = l_%s' % (ident, name))

        self.pull_locals(loop_frame, True)

        self.newline(node)
        if node.else_:
            self.writeline('l_loop = None')
        self.write('for ')
        self.visit(node.target, loop_frame)
        self.write(extended_loop and ', l_loop in LoopContext(' or ' in ')
        self.visit(node.iter, loop_frame)
        if 'loop' in aliases:
            self.write(', ' + aliases['loop'])
        self.write(extended_loop and '):' or ':')
        self.blockvisit(node.body, loop_frame)

        if node.else_:
            self.writeline('if l_loop is None:')
            self.blockvisit(node.else_, loop_frame)

        # reset the aliases and clean up
        delete = set('l_' + x for x in loop_frame.identifiers.declared_locally
                     | loop_frame.identifiers.declared_parameter)
        if extended_loop:
            delete.add('l_loop')
        for name, alias in aliases.iteritems():
            self.writeline('l_%s = %s' % (name, alias))
            delete.add(alias)
            delete.discard('l_' + name)
        self.writeline('del %s' % ', '.join(delete))

    def visit_If(self, node, frame):
        self.writeline('if ', node)
        self.visit(node.test, frame)
        self.write(':')
        self.blockvisit(node.body, frame)
        if node.else_:
            self.writeline('else:')
            self.blockvisit(node.else_, frame)

    def visit_Macro(self, node, frame):
        macro_frame = frame.inner()
        macro_frame.inspect(node.iter_child_nodes(), hard_scope=True)

        # variables that are undeclared (accessed before declaration) and
        # declared locally *and* part of an outside scope raise a template
        # assertion error. Reason: we can't generate reasonable code from
        # it without aliasing all the variables.  XXX: alias them ^^
        overriden_closure_vars = (
            macro_frame.identifiers.undeclared &
            macro_frame.identifiers.declared &
            (macro_frame.identifiers.declared_locally |
             macro_frame.identifiers.declared_parameter)
        )
        if overriden_closure_vars:
            vars = ', '.join(sorted(overriden_closure_vars))
            raise TemplateAssertionError('It\'s not possible to set and '
                                         'access variables derived from '
                                         'an outer scope! (affects: %s' %
                                         vars, node.lineno, self.filename)

        # remove variables from a closure from the frame's undeclared
        # identifiers.
        macro_frame.identifiers.undeclared -= (
            macro_frame.identifiers.undeclared &
            macro_frame.identifiers.declared
        )

        args = ['l_' + x.name for x in node.args]
        if 'arguments' in macro_frame.identifiers.undeclared:
            accesses_arguments = True
            args.append('l_arguments')
        else:
            accesses_arguments = False
        self.writeline('def macro(%s):' % ', '.join(args), node)
        self.indent()
        self.writeline('if 0: yield None')
        self.outdent()
        self.pull_locals(macro_frame)
        self.blockvisit(node.body, macro_frame)
        self.newline()
        if frame.toplevel:
            self.write('context[%r] = ' % node.name)
        arg_tuple = ', '.join(repr(x.name) for x in node.args)
        if len(node.args) == 1:
            arg_tuple += ','
        self.write('l_%s = Macro(macro, %r, (%s), (' % (node.name, node.name,
                                                       arg_tuple))
        for arg in node.defaults:
            self.visit(arg)
            self.write(', ')
        self.write('), %r, make_undefined)' % accesses_arguments)

    def visit_ExprStmt(self, node, frame):
        self.newline(node)
        self.visit(node, frame)

    def visit_Output(self, node, frame):
        self.newline(node)

        # try to evaluate as many chunks as possible into a static
        # string at compile time.
        body = []
        for child in node.nodes:
            try:
                const = unicode(child.as_const())
            except:
                body.append(child)
                continue
            if body and isinstance(body[-1], list):
                body[-1].append(const)
            else:
                body.append([const])

        # if we have less than 3 nodes we just yield them
        if len(body) < 3:
            for item in body:
                if isinstance(item, list):
                    self.writeline('yield %s' % repr(u''.join(item)))
                else:
                    self.newline(item)
                    self.write('yield unicode(')
                    self.visit(item, frame)
                    self.write(')')

        # otherwise we create a format string as this is faster in that case
        else:
            format = []
            arguments = []
            for item in body:
                if isinstance(item, list):
                    format.append(u''.join(item).replace('%', '%%'))
                else:
                    format.append('%s')
                    arguments.append(item)
            self.writeline('yield %r %% (' % u''.join(format))
            idx = -1
            for idx, argument in enumerate(arguments):
                if idx:
                    self.write(', ')
                self.visit(argument, frame)
            self.write(idx == 0 and ',)' or ')')

    def visit_Assign(self, node, frame):
        self.newline(node)
        # toplevel assignments however go into the local namespace and
        # the current template's context.  We create a copy of the frame
        # here and add a set so that the Name visitor can add the assigned
        # names here.
        if frame.toplevel:
            assignment_frame = frame.copy()
            assignment_frame.assigned_names = set()
        else:
            assignment_frame = frame
        self.visit(node.target, assignment_frame)
        self.write(' = ')
        self.visit(node.node, frame)

        # make sure toplevel assignments are added to the context.
        if frame.toplevel:
            for name in assignment_frame.assigned_names:
                self.writeline('context[%r] = l_%s' % (name, name))

    def visit_Name(self, node, frame):
        if frame.toplevel and node.ctx == 'store':
            frame.assigned_names.add(node.name)
        self.write('l_' + node.name)

    def visit_Const(self, node, frame):
        val = node.value
        if isinstance(val, float):
            # XXX: add checks for infinity and nan
            self.write(str(val))
        else:
            self.write(repr(val))

    def visit_Tuple(self, node, frame):
        self.write('(')
        idx = -1
        for idx, item in enumerate(node.items):
            if idx:
                self.write(', ')
            self.visit(item, frame)
        self.write(idx == 0 and ',)' or ')')

    def binop(operator):
        def visitor(self, node, frame):
            self.write('(')
            self.visit(node.left, frame)
            self.write(' %s ' % operator)
            self.visit(node.right, frame)
            self.write(')')
        return visitor

    def uaop(operator):
        def visitor(self, node, frame):
            self.write('(' + operator)
            self.visit(node.node)
            self.write(')')
        return visitor

    visit_Add = binop('+')
    visit_Sub = binop('-')
    visit_Mul = binop('*')
    visit_Div = binop('/')
    visit_FloorDiv = binop('//')
    visit_Pow = binop('**')
    visit_Mod = binop('%')
    visit_And = binop('and')
    visit_Or = binop('or')
    visit_Pos = uaop('+')
    visit_Neg = uaop('-')
    visit_Not = uaop('not ')
    del binop, uaop

    def visit_Compare(self, node, frame):
        self.visit(node.expr, frame)
        for op in node.ops:
            self.visit(op, frame)

    def visit_Operand(self, node, frame):
        self.write(' %s ' % operators[node.op])
        self.visit(node.expr, frame)

    def visit_Subscript(self, node, frame):
        if isinstance(node.arg, nodes.Slice):
            self.visit(node.node, frame)
            self.write('[')
            self.visit(node.arg, frame)
            self.write(']')
            return
        try:
            const = node.arg.as_const()
            have_const = True
        except nodes.Impossible:
            have_const = False
        if have_const:
            if isinstance(const, (int, long, float)):
                self.visit(node.node, frame)
                self.write('[%s]' % const)
                return
        self.write('subscribe(')
        self.visit(node.node, frame)
        self.write(', ')
        if have_const:
            self.write(repr(const))
        else:
            self.visit(node.arg, frame)
        self.write(', make_undefined)')

    def visit_Slice(self, node, frame):
        if node.start is not None:
            self.visit(node.start, frame)
        self.write(':')
        if node.stop is not None:
            self.visit(node.stop, frame)
        if node.step is not None:
            self.write(':')
            self.visit(node.step, frame)

    def visit_Filter(self, node, frame):
        for filter in node.filters:
            if filter.name in frame.identifiers.declared_filter:
                self.write('f_%s(' % filter.name)
            else:
                self.write('context.filter[%r](' % filter.name)
        self.visit(node.node, frame)
        for filter in reversed(node.filters):
            self.signature(filter, frame)
            self.write(')')

    def visit_Test(self, node, frame):
        self.write('context.tests[%r](')
        self.visit(node.node, frame)
        self.signature(node, frame)
        self.write(')')

    def visit_Call(self, node, frame):
        self.visit(node.node, frame)
        self.write('(')
        self.signature(node, frame, False)
        self.write(')')

    def visit_Keyword(self, node, frame):
        self.visit(node.key, frame)
        self.write('=')
        self.visit(node.value, frame)