vim-python-docstring/python/ibis/nodes.py at master · pixelneo/vim-python-docstring · GitHub

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# --------------------------------------------------------------------------

# Default node classes and associated helpers. Additional node classes can

# be registered using the `@register` decorator:

# @ibis.nodes.register('tag')

# Node classes can be given block scope by specifying the required end tag:

# @ibis.nodes.register('tag', 'endtag')

# --------------------------------------------------------------------------

import ast

import operator

import re

import itertools

import collections

from . import config

from . import utils

from . import filters

from .errors import (

TemplateSyntaxError,

InvalidFilter,

FilterError,

CallError,

UnpackingError,

)

# Dictionary of registered node classes.

nodemap = { 'endtags': [] }

def register(tag, end_tag=None):

""" Decorator function for registering node classes. """

def register_node_class(node_class):

node_class.end_tag = end_tag

nodemap[tag] = node_class

if end_tag:

nodemap['endtags'].append(end_tag)

return node_class

return register_node_class

class Expression:

""" Helper class for evaluating expression strings.

An Expression object is initialized with an expression string

parsed from a template. An expression string can contain a variable

name or a Python literal, optionally followed by a sequence of filters.

The Expression object handles the rather convoluted process of parsing

the string, evaluating the literal or resolving the variable, calling

the variable if it resolves to a callable, and applying the filters to

the resulting object. The consumer simply needs to call the expression's

.eval() method and supply an appropriate Context object.

Examples of valid expression syntax include:

foo.bar.baz|default:'bam'|escape

'foo', 'bar', 'baz'|random

Arguments can be passed to callables using colon or bracket syntax:

foo.bar.baz:'bam'|filter:25:'text'

foo.bar.baz('bam')|filter(25, 'text')

"""

re_callable = re.compile(r'^([a-zA-Z_][a-zA-Z0-9_.]*)[(](.*)[)]$')

def __init__(self, expr):

self.expr = expr.strip()

self.filters = []

elements = utils.splitc(expr, '|', strip=True)

self._parse_expression(elements[0])

self._parse_filters(elements[1:])

if self.is_literal:

self.literal = self._apply_filters(self.literal)

def eval(self, context):

if self.is_literal:

return self.literal

else:

return self._resolve_variable(context)

def _parse_expression(self, expr):

try:

self.literal = ast.literal_eval(expr)

self.is_literal = True

except:

self.varstr, self.varargs = self._parse_callable(expr)

self.is_literal = False

def _resolve_variable(self, context):

obj = context.resolve(self.varstr)

if callable(obj):

try:

obj = obj(*self.varargs)

except:

raise CallError("error calling [%s]" % self.varstr)

return self._apply_filters(obj)

def _parse_callable(self, callable):

match = self.re_callable.match(callable)

if match:

name = match.group(1)

args = utils.splitc(match.group(2), ',', True, True)

else:

elements = utils.splitc(callable, ':', True)

name = elements[0]

args = elements[1:]

for index, arg in enumerate(args):

try:

args[index] = ast.literal_eval(arg)

except:

msg = "unparsable argument: [%s] in [%s]" % (arg, self.expr)

raise TemplateSyntaxError(msg) from None

return name, args

def _parse_filters(self, filterlist):

for filter in filterlist:

name, args = self._parse_callable(filter)

if name in filters.filtermap:

self.filters.append((name, filters.filtermap[name], args))

else:

msg = "[%s] is not a recognised filter"

raise InvalidFilter(msg % name)

def _apply_filters(self, obj):

for name, func, args in self.filters:

try:

obj = func(obj, *args)

except:

msg = "error applying filter [%s] in [%s]"

raise FilterError(msg % (name, self.expr))

return obj

@register('node')

class Node:

""" Base class for all node objects. """

def __init__(self, token=None, children=None):

self.token = token

self.children = children or []

self.process_token(token)

def __iter__(self):

for child in self.children:

yield child

def __repr__(self):

return self.repr()

def render(self, context):

""" Render the node as a string. """

return ''.join(child.render(context) for child in self.children)

def process_token(self, token):

""" Subclasses can override this method to process token content

for arguments, etc. """

pass

def exit_scope(self):

""" Subclasses can override this method to process the content of

block-scoped nodes. """

pass

def split_children(self, delimiter_class):

""" Splits child nodes on the first instance of a delimiter class. """

for index, child in enumerate(self):

if isinstance(child, delimiter_class):

return self.children[:index], child, self.children[index+1:]

return self.children, None, []

def repr(self, depth=0):

""" Basic tree-printing capability for debugging. """

output = '· ' * depth + '<%s>\n' % self.__class__.__name__

for child in self.children:

output += child.repr(depth + 1)

return output

@register('root')

class RootNode(Node):

""" Root node of a template tree. """

pass

@register('text')

class TextNode(Node):

""" Plain text. """

def render(self, context):

return self.token.content

@register('print')

class PrintNode(Node):

""" Evaluates an expression and prints its result.

Multiple expressions can be listed separated by 'or' or '||'.

The first expression to resolve to a truthy value will be

printed. (If none of the expressions are truthy the final value

will be printed regardless.)

Alternatively, print statements can use the ternary operator: ?? ::

If <test-expr> is truthy, <expr1> will be printed, otherwise <expr2>

will be printed.

Note that *either* 'or'-chaining or the ternary operator can be used

in a single print statement, but not both.

"""

escape = False

def process_token(self, token):

# Check for a ternary operator.

chunks = utils.splitre(token.content, (r'\?\?', r'\:\:'), True)

if len(chunks) == 5 and chunks[1] == '??' and chunks[3] == '::':

self.is_ternary = True

self.testexpr = Expression(chunks[0])

self.iftrue = Expression(chunks[2])

self.iffalse = Expression(chunks[4])

# Look for a list of 'or' separated expressions.

else:

self.is_ternary = False

exprs = utils.splitre(token.content, (r'\s+or\s+', r'\|\|'))

self.exprs = [Expression(e) for e in exprs]

def render(self, context):

if self.is_ternary:

if self.testexpr.eval(context):

content = self.iftrue.eval(context)

else:

content = self.iffalse.eval(context)

else:

for expr in self.exprs:

content = expr.eval(context)

if content:

break

if self.escape:

return filters.filtermap['escape'](str(content))

else:

return str(content)

@register('eprint')

class EscapedPrintNode(PrintNode):

""" Print node with automatic escaping. """

escape = True

@register('for', 'endfor')

class ForNode(Node):

""" Implements for/empty looping over an iterable expression.

{% for <var> in <expr> %} ... [ {% empty %} ... ] {% endfor %}

Supports unpacking into multiple loop variables:

{% for <var1>, <var2> in <expr> %}

"""

regex = re.compile(r'for\s+(\w+(?:,\s*\w+)*)\s+in\s+(.+)')

def process_token(self, token):

match = self.regex.match(token.content)

if match is None:

msg = "malformed [for] tag: [%s]" % token.content

raise TemplateSyntaxError(msg)

self.loopvars = [var.strip() for var in match.group(1).split(',')]

self.expr = Expression(match.group(2))

def render(self, context):

items = self.expr.eval(context)

if items and hasattr(items, '__iter__'):

items = list(items)

length = len(items)

unpack = len(self.loopvars) > 1

output = []

for index, item in enumerate(items):

context.push()

if unpack:

try:

unpacked = dict(zip(self.loopvars, item))

except TypeError:

msg = 'cannot unpack [%s] in [%s]' % (

repr(item), self.token.content

)

raise UnpackingError(msg)

else:

context.update(unpacked)

else:

context[self.loopvars[0]] = item

context['loop'] = {

'index': index,

'count': index + 1,

'length': length,

'is_first': index == 0,

'first': index == 0, # deprecated - will be removed

'is_last': index == length - 1,

'last': index == length - 1, # deprecated - will be removed

'parent': context.get('loop'),

}

output.append(self.for_branch.render(context))

context.pop()

return ''.join(output)

else:

return self.empty_branch.render(context)

def exit_scope(self):

fornodes, emptynode, emptynodes = self.split_children(EmptyNode)

self.for_branch = Node(None, fornodes)

self.empty_branch = Node(None, emptynodes)

@register('empty')

class EmptyNode(Node):

""" Delimiter node to implement for/empty branching. """

pass

@register('if', 'endif')

class IfNode(Node):

""" Implements if/elif/else branching.

{% if [not] <expr> %} ... {% endif %}

{% if [not] <expr> <operator> <expr> %} ... {% endif %}

{% if <...> %} ... {% elif <...> %} ... {% else %} ... {% endif %}

Supports 'and' and 'or' conjunctions; 'and' has higher precedence so:

if a and b or c and d

is treated as:

if (a and b) or (c and d)

Note that explicit brackets are not supported.

"""

condition = collections.namedtuple('Condition', 'negated lhs op rhs')

re_condition = re.compile(r'''

(not\s+)?(.+?)\s+(==|!=|<|>|<=|>=|not[ ]in|in)\s+(.+)

(not\s+)?(.+)

''', re.VERBOSE

)

operators = {

'==': operator.eq,

'!=': operator.ne,

'<': operator.lt,

'>': operator.gt,

'<=': operator.le,

'>=': operator.ge,

'in': lambda a, b: a in b,

'not in': lambda a, b: a not in b,

}

def process_token(self, token):

try:

tag, conditions = token.content.split(None, 1)

except ValueError:

msg = "malformed [%s] tag: [%s]" % (token.tag, token.content)

raise TemplateSyntaxError(msg) from None

self.condition_groups = [

[

self.parse_condition(condstr)

for condstr in utils.splitre(or_block, (r'\s+and\s+', r'&&'))

]

for or_block in utils.splitre(conditions, (r'\s+or\s+', r'\|\|'))

]

def parse_condition(self, condstr):

match = self.re_condition.match(condstr)

if match.group(2):

return self.condition(

negated = bool(match.group(1)),

lhs = Expression(match.group(2)),

op = self.operators[match.group(3)],

rhs = Expression(match.group(4)),

)

else:

return self.condition(

negated = bool(match.group(5)),

lhs = Expression(match.group(6)),

op = None,

rhs = None,

)

def eval_condition(self, cond, context):

try:

if cond.op:

result = cond.op(cond.lhs.eval(context), cond.rhs.eval(context))

else:

result = operator.truth(cond.lhs.eval(context))

except:

# We treat an exception during evaluation as a false result.

# We should probably raise an exception of our own here instead.

result = False

if cond.negated:

result = not result

return result

def render(self, context):

for condition_group in self.condition_groups:

for condition in condition_group:

is_true = self.eval_condition(condition, context)

if not is_true:

break

if is_true:

break

if is_true:

return self.true_branch.render(context)

else:

return self.false_branch.render(context)

def exit_scope(self):

ifnodes, elifnode, elifnodes = self.split_children(ElifNode)

if elifnode:

self.true_branch = Node(None, ifnodes)

self.false_branch = IfNode(elifnode.token, elifnodes)

self.false_branch.exit_scope()

return

ifnodes, elsenode, elsenodes = self.split_children(ElseNode)

self.true_branch = Node(None, ifnodes)

self.false_branch = Node(None, elsenodes)

@register('elif')

class ElifNode(Node):

""" Delimiter node to implement if/elif branching. """

pass

@register('else')

class ElseNode(Node):

""" Delimiter node to implement if/else branching. """

pass

@register('cycle')

class CycleNode(Node):

""" Cycles over an iterable expression.

{% cycle <expr> %}

Each time the node is evaluated it will render the next value in the

sequence, looping once it reaches the end; e.g.

{% cycle 'odd', 'even' %}

will alternate continuously between printing 'odd' and 'even'.

"""

def process_token(self, token):

try:

tag, arg = token.content.split(None, 1)

except ValueError:

msg = "malformed [cycle] tag: [%s]" % token.content

raise TemplateSyntaxError(msg) from None

self.expr = Expression(arg)

def render(self, context):

# We store our state info on the context object to avoid a threading

# mess if the template is being simultaneously rendered by multiple

# threads.

if not self in context.stash:

items = self.expr.eval(context)

if not hasattr(items, '__iter__'):

items = ''

context.stash[self] = itertools.cycle(items)

iterator = context.stash[self]

return str(next(iterator, ''))

@register('include')

class IncludeNode(Node):

""" Includes a sub-template.

{% include <expr> %}

Requires a template ID which can be supplied as either a string literal

or a variable resolving to a string. This ID will be passed to the

registered template loader.

"""

def process_token(self, token):

try:

tag, arg = token.content.split(None, 1)

except ValueError:

msg = "malformed [include] tag: [%s]" % token.content

raise TemplateSyntaxError(msg) from None

expr = Expression(arg)

if expr.is_literal:

template = config.loader(expr.literal)

self.children.append(template.root)

else:

self.expr = expr

def render(self, context):

if self.children:

return ''.join(child.render(context) for child in self)

else:

template_id = self.expr.eval(context)

template = config.loader(template_id)

return template.root.render(context)

@register('extends')

class ExtendsNode(Node):

""" Specifies a parent template.

Indicates that the current template inherits from or 'extends' the

specified parent template.

{% extends "parent.txt" %}

Requires a template ID to pass to the registered template loader.

This must be supplied as a string literal (not a variable)

as the parent template must be loaded at compile-time.

"""

def process_token(self, token):

try:

tag, arg = token.content.split(None, 1)

except ValueError:

msg = "malformed [extends] tag: [%s]" % token.content

raise TemplateSyntaxError(msg) from None

expr = Expression(arg)

if expr.is_literal:

template = config.loader(expr.literal)

self.children.append(template.root)

else:

msg = "malformed [extends] tag: [%s]" % token.content

raise TemplateSyntaxError(msg) from None

@register('block', 'endblock')

class BlockNode(Node):

""" Implements template inheritance.

{% block title %} ... {% endblock %}

A block tag defines a titled block of content that can be overridden

by similarly titled blocks in child templates.

"""

def process_token(self, token):

self.title = token.content[5:].strip()

def render(self, context):

# We only want to render the first block of any given title

# that we encounter in the node tree, although we want to substitute

# the content of the last block of that title in its place.

block_list = context.template.registry[self.title]

if block_list[0] is self:

return self.render_block(context, block_list[:])

else:

return ''

def render_block(self, context, block_list):

# A call to {{ super }} inside a block renders and returns the

# content of the block's immediate ancestor. That ancestor may

# itself contain a {{ super }} call, so we start at the end of the

# list and recursively work our way backwards, popping off nodes

# as we go.

if block_list:

last_block = block_list.pop()

context.push()

context['super'] = lambda: self.render_block(context, block_list)

output = ''.join(child.render(context) for child in last_block)

context.pop()

return output

else:

return ''

@register('spaceless', 'endspaceless')

class SpacelessNode(Node):

""" Strips all whitespace between HTML tags.

{% spaceless %} ... {% endspaceless %}

"""

def render(self, context):

output = ''.join(child.render(context) for child in self)

return filters.filtermap['spaceless'](output).strip()

@register('trim', 'endtrim')

class TrimNode(Node):

""" Trims leading and trailing whitespace.

{% trim %} ... {% endtrim %}

"""

def render(self, context):

return ''.join(child.render(context) for child in self).strip()

@register('with', 'endwith')

class WithNode(Node):

""" Caches a complex expression under a simpler alias.

{% with <alias> = <expr> %} ... {% endwith %}

"""

def process_token(self, token):

try:

alias, expr = token.content[4:].split('=', 1)

except ValueError:

msg = "malformed [with] tag: [%s]" % token.content

raise TemplateSyntaxError(msg) from None

self.alias = alias.strip()

self.expr = Expression(expr.strip())

def render(self, context):

context.push()

context[self.alias] = self.expr.eval(context)

rendered = ''.join(child.render(context) for child in self)

context.pop()

return rendered

vim-python-docstring/python/ibis/nodes.py at master · pixelneo/vim-python-docstring · GitHub

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