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import railroad
import pyparsing
import typing
from typing import (
List,
NamedTuple,
Generic,
TypeVar,
Dict,
Callable,
Set,
Iterable,
)
from jinja2 import Template
from io import StringIO
import inspect
jinja2_template_source = """\
<!DOCTYPE html>
<html>
<head>
{% if not head %}
<style type="text/css">
.railroad-heading {
font-family: monospace;
}
</style>
{% else %}
{{ head | safe }}
{% endif %}
</head>
<body>
{{ body | safe }}
{% for diagram in diagrams %}
<div class="railroad-group">
<h1 class="railroad-heading">{{ diagram.title }}</h1>
<div class="railroad-description">{{ diagram.text }}</div>
<div class="railroad-svg">
{{ diagram.svg }}
</div>
</div>
{% endfor %}
</body>
</html>
"""
template = Template(jinja2_template_source)
# Note: ideally this would be a dataclass, but we're supporting Python 3.5+ so we can't do this yet
NamedDiagram = NamedTuple(
"NamedDiagram",
[("name", str), ("diagram", typing.Optional[railroad.DiagramItem]), ("index", int)],
)
"""
A simple structure for associating a name with a railroad diagram
"""
T = TypeVar("T")
class EachItem(railroad.Group):
"""
Custom railroad item to compose a:
- Group containing a
- OneOrMore containing a
- Choice of the elements in the Each
with the group label indicating that all must be matched
"""
all_label = "[ALL]"
def __init__(self, *items):
choice_item = railroad.Choice(len(items) - 1, *items)
one_or_more_item = railroad.OneOrMore(item=choice_item)
super().__init__(one_or_more_item, label=self.all_label)
class AnnotatedItem(railroad.Group):
"""
Simple subclass of Group that creates an annotation label
"""
def __init__(self, label: str, item):
super().__init__(item=item, label="[{}]".format(label) if label else label)
class EditablePartial(Generic[T]):
"""
Acts like a functools.partial, but can be edited. In other words, it represents a type that hasn't yet been
constructed.
"""
# We need this here because the railroad constructors actually transform the data, so can't be called until the
# entire tree is assembled
def __init__(self, func: Callable[..., T], args: list, kwargs: dict):
self.func = func
self.args = args
self.kwargs = kwargs
@classmethod
def from_call(cls, func: Callable[..., T], *args, **kwargs) -> "EditablePartial[T]":
"""
If you call this function in the same way that you would call the constructor, it will store the arguments
as you expect. For example EditablePartial.from_call(Fraction, 1, 3)() == Fraction(1, 3)
"""
return EditablePartial(func=func, args=list(args), kwargs=kwargs)
@property
def name(self):
return self.kwargs["name"]
def __call__(self) -> T:
"""
Evaluate the partial and return the result
"""
args = self.args.copy()
kwargs = self.kwargs.copy()
# This is a helpful hack to allow you to specify varargs parameters (e.g. *args) as keyword args (e.g.
# args=['list', 'of', 'things'])
arg_spec = inspect.getfullargspec(self.func)
if arg_spec.varargs in self.kwargs:
args += kwargs.pop(arg_spec.varargs)
return self.func(*args, **kwargs)
def railroad_to_html(diagrams: List[NamedDiagram], **kwargs) -> str:
"""
Given a list of NamedDiagram, produce a single HTML string that visualises those diagrams
:params kwargs: kwargs to be passed in to the template
"""
data = []
for diagram in diagrams:
if diagram.diagram is None:
continue
io = StringIO()
diagram.diagram.writeSvg(io.write)
title = diagram.name
if diagram.index == 0:
title += " (root)"
data.append({"title": title, "text": "", "svg": io.getvalue()})
return template.render(diagrams=data, **kwargs)
def resolve_partial(partial: "EditablePartial[T]") -> T:
"""
Recursively resolves a collection of Partials into whatever type they are
"""
if isinstance(partial, EditablePartial):
partial.args = resolve_partial(partial.args)
partial.kwargs = resolve_partial(partial.kwargs)
return partial()
elif isinstance(partial, list):
return [resolve_partial(x) for x in partial]
elif isinstance(partial, dict):
return {key: resolve_partial(x) for key, x in partial.items()}
else:
return partial
def to_railroad(
element: pyparsing.ParserElement,
diagram_kwargs: typing.Optional[dict] = None,
vertical: int = 3,
show_results_names: bool = False,
show_groups: bool = False,
) -> List[NamedDiagram]:
"""
Convert a pyparsing element tree into a list of diagrams. This is the recommended entrypoint to diagram
creation if you want to access the Railroad tree before it is converted to HTML
:param element: base element of the parser being diagrammed
:param diagram_kwargs: kwargs to pass to the Diagram() constructor
:param vertical: (optional) - int - limit at which number of alternatives should be
shown vertically instead of horizontally
:param show_results_names - bool to indicate whether results name annotations should be
included in the diagram
:param show_groups - bool to indicate whether groups should be highlighted with an unlabeled
surrounding box
"""
# Convert the whole tree underneath the root
lookup = ConverterState(diagram_kwargs=diagram_kwargs or {})
_to_diagram_element(
element,
lookup=lookup,
parent=None,
vertical=vertical,
show_results_names=show_results_names,
show_groups=show_groups,
)
root_id = id(element)
# Convert the root if it hasn't been already
if root_id in lookup:
if not element.customName:
lookup[root_id].name = ""
lookup[root_id].mark_for_extraction(root_id, lookup, force=True)
# Now that we're finished, we can convert from intermediate structures into Railroad elements
diags = list(lookup.diagrams.values())
if len(diags) > 1:
# collapse out duplicate diags with the same name
seen = set()
deduped_diags = []
for d in diags:
# don't extract SkipTo elements, they are uninformative as subdiagrams
if d.name == "...":
continue
if d.name is not None and d.name not in seen:
seen.add(d.name)
deduped_diags.append(d)
resolved = [resolve_partial(partial) for partial in deduped_diags]
else:
# special case - if just one diagram, always display it, even if
# it has no name
resolved = [resolve_partial(partial) for partial in diags]
return sorted(resolved, key=lambda diag: diag.index)
def _should_vertical(
specification: int, exprs: Iterable[pyparsing.ParserElement]
) -> bool:
"""
Returns true if we should return a vertical list of elements
"""
if specification is None:
return False
else:
return len(_visible_exprs(exprs)) >= specification
class ElementState:
"""
State recorded for an individual pyparsing Element
"""
# Note: this should be a dataclass, but we have to support Python 3.5
def __init__(
self,
element: pyparsing.ParserElement,
converted: EditablePartial,
parent: EditablePartial,
number: int,
name: str = None,
parent_index: typing.Optional[int] = None,
):
#: The pyparsing element that this represents
self.element: pyparsing.ParserElement = element
#: The name of the element
self.name: typing.Optional[str] = name
#: The output Railroad element in an unconverted state
self.converted: EditablePartial = converted
#: The parent Railroad element, which we store so that we can extract this if it's duplicated
self.parent: EditablePartial = parent
#: The order in which we found this element, used for sorting diagrams if this is extracted into a diagram
self.number: int = number
#: The index of this inside its parent
self.parent_index: typing.Optional[int] = parent_index
#: If true, we should extract this out into a subdiagram
self.extract: bool = False
#: If true, all of this element's children have been filled out
self.complete: bool = False
def mark_for_extraction(
self, el_id: int, state: "ConverterState", name: str = None, force: bool = False
):
"""
Called when this instance has been seen twice, and thus should eventually be extracted into a sub-diagram
:param el_id: id of the element
:param state: element/diagram state tracker
:param name: name to use for this element's text
:param force: If true, force extraction now, regardless of the state of this. Only useful for extracting the
root element when we know we're finished
"""
self.extract = True
# Set the name
if not self.name:
if name:
# Allow forcing a custom name
self.name = name
elif self.element.customName:
self.name = self.element.customName
else:
self.name = ""
# Just because this is marked for extraction doesn't mean we can do it yet. We may have to wait for children
# to be added
# Also, if this is just a string literal etc, don't bother extracting it
if force or (self.complete and _worth_extracting(self.element)):
state.extract_into_diagram(el_id)
class ConverterState:
"""
Stores some state that persists between recursions into the element tree
"""
def __init__(self, diagram_kwargs: typing.Optional[dict] = None):
#: A dictionary mapping ParserElements to state relating to them
self._element_diagram_states: Dict[int, ElementState] = {}
#: A dictionary mapping ParserElement IDs to subdiagrams generated from them
self.diagrams: Dict[int, EditablePartial[NamedDiagram]] = {}
#: The index of the next unnamed element
self.unnamed_index: int = 1
#: The index of the next element. This is used for sorting
self.index: int = 0
#: Shared kwargs that are used to customize the construction of diagrams
self.diagram_kwargs: dict = diagram_kwargs or {}
self.extracted_diagram_names: Set[str] = set()
def __setitem__(self, key: int, value: ElementState):
self._element_diagram_states[key] = value
def __getitem__(self, key: int) -> ElementState:
return self._element_diagram_states[key]
def __delitem__(self, key: int):
del self._element_diagram_states[key]
def __contains__(self, key: int):
return key in self._element_diagram_states
def generate_unnamed(self) -> int:
"""
Generate a number used in the name of an otherwise unnamed diagram
"""
self.unnamed_index += 1
return self.unnamed_index
def generate_index(self) -> int:
"""
Generate a number used to index a diagram
"""
self.index += 1
return self.index
def extract_into_diagram(self, el_id: int):
"""
Used when we encounter the same token twice in the same tree. When this
happens, we replace all instances of that token with a terminal, and
create a new subdiagram for the token
"""
position = self[el_id]
# Replace the original definition of this element with a regular block
if position.parent:
ret = EditablePartial.from_call(railroad.NonTerminal, text=position.name)
if "item" in position.parent.kwargs:
position.parent.kwargs["item"] = ret
elif "items" in position.parent.kwargs:
position.parent.kwargs["items"][position.parent_index] = ret
# If the element we're extracting is a group, skip to its content but keep the title
if position.converted.func == railroad.Group:
content = position.converted.kwargs["item"]
else:
content = position.converted
self.diagrams[el_id] = EditablePartial.from_call(
NamedDiagram,
name=position.name,
diagram=EditablePartial.from_call(
railroad.Diagram, content, **self.diagram_kwargs
),
index=position.number,
)
del self[el_id]
def _worth_extracting(element: pyparsing.ParserElement) -> bool:
"""
Returns true if this element is worth having its own sub-diagram. Simply, if any of its children
themselves have children, then its complex enough to extract
"""
children = element.recurse()
return any(child.recurse() for child in children)
def _apply_diagram_item_enhancements(fn):
"""
decorator to ensure enhancements to a diagram item (such as results name annotations)
get applied on return from _to_diagram_element (we do this since there are several
returns in _to_diagram_element)
"""
def _inner(
element: pyparsing.ParserElement,
parent: typing.Optional[EditablePartial],
lookup: ConverterState = None,
vertical: int = None,
index: int = 0,
name_hint: str = None,
show_results_names: bool = False,
show_groups: bool = False,
) -> typing.Optional[EditablePartial]:
ret = fn(
element,
parent,
lookup,
vertical,
index,
name_hint,
show_results_names,
show_groups,
)
# apply annotation for results name, if present
if show_results_names and ret is not None:
element_results_name = element.resultsName
if element_results_name:
# add "*" to indicate if this is a "list all results" name
element_results_name += "" if element.modalResults else "*"
ret = EditablePartial.from_call(
railroad.Group, item=ret, label=element_results_name
)
return ret
return _inner
def _visible_exprs(exprs: Iterable[pyparsing.ParserElement]):
non_diagramming_exprs = (
pyparsing.ParseElementEnhance,
pyparsing.PositionToken,
pyparsing.And._ErrorStop,
)
return [
e
for e in exprs
if not (e.customName or e.resultsName or isinstance(e, non_diagramming_exprs))
]
@_apply_diagram_item_enhancements
def _to_diagram_element(
element: pyparsing.ParserElement,
parent: typing.Optional[EditablePartial],
lookup: ConverterState = None,
vertical: int = None,
index: int = 0,
name_hint: str = None,
show_results_names: bool = False,
show_groups: bool = False,
) -> typing.Optional[EditablePartial]:
"""
Recursively converts a PyParsing Element to a railroad Element
:param lookup: The shared converter state that keeps track of useful things
:param index: The index of this element within the parent
:param parent: The parent of this element in the output tree
:param vertical: Controls at what point we make a list of elements vertical. If this is an integer (the default),
it sets the threshold of the number of items before we go vertical. If True, always go vertical, if False, never
do so
:param name_hint: If provided, this will override the generated name
:param show_results_names: bool flag indicating whether to add annotations for results names
:returns: The converted version of the input element, but as a Partial that hasn't yet been constructed
:param show_groups: bool flag indicating whether to show groups using bounding box
"""
exprs = element.recurse()
name = name_hint or element.customName or element.__class__.__name__
# Python's id() is used to provide a unique identifier for elements
el_id = id(element)
element_results_name = element.resultsName
# Here we basically bypass processing certain wrapper elements if they contribute nothing to the diagram
if not element.customName:
if isinstance(
element,
(
# pyparsing.TokenConverter,
# pyparsing.Forward,
pyparsing.Located,
),
):
# However, if this element has a useful custom name, and its child does not, we can pass it on to the child
if exprs:
if not exprs[0].customName:
propagated_name = name
else:
propagated_name = None
return _to_diagram_element(
element.expr,
parent=parent,
lookup=lookup,
vertical=vertical,
index=index,
name_hint=propagated_name,
show_results_names=show_results_names,
show_groups=show_groups,
)
# If the element isn't worth extracting, we always treat it as the first time we say it
if _worth_extracting(element):
if el_id in lookup:
# If we've seen this element exactly once before, we are only just now finding out that it's a duplicate,
# so we have to extract it into a new diagram.
looked_up = lookup[el_id]
looked_up.mark_for_extraction(el_id, lookup, name=name_hint)
ret = EditablePartial.from_call(railroad.NonTerminal, text=looked_up.name)
return ret
elif el_id in lookup.diagrams:
# If we have seen the element at least twice before, and have already extracted it into a subdiagram, we
# just put in a marker element that refers to the sub-diagram
ret = EditablePartial.from_call(
railroad.NonTerminal, text=lookup.diagrams[el_id].kwargs["name"]
)
return ret
# Recursively convert child elements
# Here we find the most relevant Railroad element for matching pyparsing Element
# We use ``items=[]`` here to hold the place for where the child elements will go once created
if isinstance(element, pyparsing.And):
# detect And's created with ``expr*N`` notation - for these use a OneOrMore with a repeat
# (all will have the same name, and resultsName)
if not exprs:
return None
if len(set((e.name, e.resultsName) for e in exprs)) == 1:
ret = EditablePartial.from_call(
railroad.OneOrMore, item="", repeat=str(len(exprs))
)
elif _should_vertical(vertical, exprs):
ret = EditablePartial.from_call(railroad.Stack, items=[])
else:
ret = EditablePartial.from_call(railroad.Sequence, items=[])
elif isinstance(element, (pyparsing.Or, pyparsing.MatchFirst)):
if not exprs:
return None
if _should_vertical(vertical, exprs):
ret = EditablePartial.from_call(railroad.Choice, 0, items=[])
else:
ret = EditablePartial.from_call(railroad.HorizontalChoice, items=[])
elif isinstance(element, pyparsing.Each):
if not exprs:
return None
ret = EditablePartial.from_call(EachItem, items=[])
elif isinstance(element, pyparsing.NotAny):
ret = EditablePartial.from_call(AnnotatedItem, label="NOT", item="")
elif isinstance(element, pyparsing.FollowedBy):
ret = EditablePartial.from_call(AnnotatedItem, label="LOOKAHEAD", item="")
elif isinstance(element, pyparsing.PrecededBy):
ret = EditablePartial.from_call(AnnotatedItem, label="LOOKBEHIND", item="")
elif isinstance(element, pyparsing.Group):
if show_groups:
ret = EditablePartial.from_call(AnnotatedItem, label="", item="")
else:
ret = EditablePartial.from_call(railroad.Group, label="", item="")
elif isinstance(element, pyparsing.TokenConverter):
ret = EditablePartial.from_call(
AnnotatedItem, label=type(element).__name__.lower(), item=""
)
elif isinstance(element, pyparsing.Opt):
ret = EditablePartial.from_call(railroad.Optional, item="")
elif isinstance(element, pyparsing.OneOrMore):
ret = EditablePartial.from_call(railroad.OneOrMore, item="")
elif isinstance(element, pyparsing.ZeroOrMore):
ret = EditablePartial.from_call(railroad.ZeroOrMore, item="")
elif isinstance(element, pyparsing.Group):
ret = EditablePartial.from_call(
railroad.Group, item=None, label=element_results_name
)
elif isinstance(element, pyparsing.Empty) and not element.customName:
# Skip unnamed "Empty" elements
ret = None
elif len(exprs) > 1:
ret = EditablePartial.from_call(railroad.Sequence, items=[])
elif len(exprs) > 0 and not element_results_name:
ret = EditablePartial.from_call(railroad.Group, item="", label=name)
else:
terminal = EditablePartial.from_call(railroad.Terminal, element.defaultName)
ret = terminal
if ret is None:
return
# Indicate this element's position in the tree so we can extract it if necessary
lookup[el_id] = ElementState(
element=element,
converted=ret,
parent=parent,
parent_index=index,
number=lookup.generate_index(),
)
if element.customName:
lookup[el_id].mark_for_extraction(el_id, lookup, element.customName)
i = 0
for expr in exprs:
# Add a placeholder index in case we have to extract the child before we even add it to the parent
if "items" in ret.kwargs:
ret.kwargs["items"].insert(i, None)
item = _to_diagram_element(
expr,
parent=ret,
lookup=lookup,
vertical=vertical,
index=i,
show_results_names=show_results_names,
show_groups=show_groups,
)
# Some elements don't need to be shown in the diagram
if item is not None:
if "item" in ret.kwargs:
ret.kwargs["item"] = item
elif "items" in ret.kwargs:
# If we've already extracted the child, don't touch this index, since it's occupied by a nonterminal
ret.kwargs["items"][i] = item
i += 1
elif "items" in ret.kwargs:
# If we're supposed to skip this element, remove it from the parent
del ret.kwargs["items"][i]
# If all this items children are none, skip this item
if ret and (
("items" in ret.kwargs and len(ret.kwargs["items"]) == 0)
or ("item" in ret.kwargs and ret.kwargs["item"] is None)
):
ret = EditablePartial.from_call(railroad.Terminal, name)
# Mark this element as "complete", ie it has all of its children
if el_id in lookup:
lookup[el_id].complete = True
if el_id in lookup and lookup[el_id].extract and lookup[el_id].complete:
lookup.extract_into_diagram(el_id)
if ret is not None:
ret = EditablePartial.from_call(
railroad.NonTerminal, text=lookup.diagrams[el_id].kwargs["name"]
)
return ret
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