"""
Adapted from https://github.com/noahmorrison/chevron
MIT License
"""
from __future__ import annotations
import logging
from types import MappingProxyType
from typing import (
Any,
Dict,
Iterator,
List,
Literal,
Mapping,
Optional,
Sequence,
Tuple,
Union,
cast,
)
from typing_extensions import TypeAlias
logger = logging.getLogger(__name__)
Scopes: TypeAlias = List[Union[Literal[False, 0], Mapping[str, Any]]]
# Globals
_CURRENT_LINE = 1
_LAST_TAG_LINE = None
[docs]class ChevronError(SyntaxError):
"""Custom exception for Chevron errors."""
pass
#
# Helper functions
#
[docs]def grab_literal(template: str, l_del: str) -> Tuple[str, str]:
"""Parse a literal from the template.
Args:
template: The template to parse.
l_del: The left delimiter.
Returns:
Tuple[str, str]: The literal and the template.
"""
global _CURRENT_LINE
try:
# Look for the next tag and move the template to it
literal, template = template.split(l_del, 1)
_CURRENT_LINE += literal.count("\n")
return (literal, template)
# There are no more tags in the template?
except ValueError:
# Then the rest of the template is a literal
return (template, "")
[docs]def l_sa_check(template: str, literal: str, is_standalone: bool) -> bool:
"""Do a preliminary check to see if a tag could be a standalone.
Args:
template: The template. (Not used.)
literal: The literal.
is_standalone: Whether the tag is standalone.
Returns:
bool: Whether the tag could be a standalone.
"""
# If there is a newline, or the previous tag was a standalone
if literal.find("\n") != -1 or is_standalone:
padding = literal.split("\n")[-1]
# If all the characters since the last newline are spaces
if padding.isspace() or padding == "":
# Then the next tag could be a standalone
return True
else:
# Otherwise it can't be
return False
else:
return False
[docs]def r_sa_check(template: str, tag_type: str, is_standalone: bool) -> bool:
"""Do a final check to see if a tag could be a standalone.
Args:
template: The template.
tag_type: The type of the tag.
is_standalone: Whether the tag is standalone.
Returns:
bool: Whether the tag could be a standalone.
"""
# Check right side if we might be a standalone
if is_standalone and tag_type not in ["variable", "no escape"]:
on_newline = template.split("\n", 1)
# If the stuff to the right of us are spaces we're a standalone
if on_newline[0].isspace() or not on_newline[0]:
return True
else:
return False
# If we're a tag can't be a standalone
else:
return False
[docs]def parse_tag(template: str, l_del: str, r_del: str) -> Tuple[Tuple[str, str], str]:
"""Parse a tag from a template.
Args:
template: The template.
l_del: The left delimiter.
r_del: The right delimiter.
Returns:
Tuple[Tuple[str, str], str]: The tag and the template.
Raises:
ChevronError: If the tag is unclosed.
ChevronError: If the set delimiter tag is unclosed.
"""
global _CURRENT_LINE
global _LAST_TAG_LINE
tag_types = {
"!": "comment",
"#": "section",
"^": "inverted section",
"/": "end",
">": "partial",
"=": "set delimiter?",
"{": "no escape?",
"&": "no escape",
}
# Get the tag
try:
tag, template = template.split(r_del, 1)
except ValueError as e:
raise ChevronError("unclosed tag " f"at line {_CURRENT_LINE}") from e
# Find the type meaning of the first character
tag_type = tag_types.get(tag[0], "variable")
# If the type is not a variable
if tag_type != "variable":
# Then that first character is not needed
tag = tag[1:]
# If we might be a set delimiter tag
if tag_type == "set delimiter?":
# Double check to make sure we are
if tag.endswith("="):
tag_type = "set delimiter"
# Remove the equal sign
tag = tag[:-1]
# Otherwise we should complain
else:
raise ChevronError(
"unclosed set delimiter tag\n" f"at line {_CURRENT_LINE}"
)
# If we might be a no html escape tag
elif tag_type == "no escape?":
# And we have a third curly brace
# (And are using curly braces as delimiters)
if l_del == "{{" and r_del == "}}" and template.startswith("}"):
# Then we are a no html escape tag
template = template[1:]
tag_type = "no escape"
# Strip the whitespace off the key and return
return ((tag_type, tag.strip()), template)
#
# The main tokenizing function
#
[docs]def tokenize(
template: str, def_ldel: str = "{{", def_rdel: str = "}}"
) -> Iterator[Tuple[str, str]]:
"""Tokenize a mustache template.
Tokenizes a mustache template in a generator fashion,
using file-like objects. It also accepts a string containing
the template.
Arguments:
template -- a file-like object, or a string of a mustache template
def_ldel -- The default left delimiter
("{{" by default, as in spec compliant mustache)
def_rdel -- The default right delimiter
("}}" by default, as in spec compliant mustache)
Returns:
A generator of mustache tags in the form of a tuple
-- (tag_type, tag_key)
Where tag_type is one of:
* literal
* section
* inverted section
* end
* partial
* no escape
And tag_key is either the key or in the case of a literal tag,
the literal itself.
"""
global _CURRENT_LINE, _LAST_TAG_LINE
_CURRENT_LINE = 1
_LAST_TAG_LINE = None
is_standalone = True
open_sections = []
l_del = def_ldel
r_del = def_rdel
while template:
literal, template = grab_literal(template, l_del)
# If the template is completed
if not template:
# Then yield the literal and leave
yield ("literal", literal)
break
# Do the first check to see if we could be a standalone
is_standalone = l_sa_check(template, literal, is_standalone)
# Parse the tag
tag, template = parse_tag(template, l_del, r_del)
tag_type, tag_key = tag
# Special tag logic
# If we are a set delimiter tag
if tag_type == "set delimiter":
# Then get and set the delimiters
dels = tag_key.strip().split(" ")
l_del, r_del = dels[0], dels[-1]
# If we are a section tag
elif tag_type in ["section", "inverted section"]:
# Then open a new section
open_sections.append(tag_key)
_LAST_TAG_LINE = _CURRENT_LINE
# If we are an end tag
elif tag_type == "end":
# Then check to see if the last opened section
# is the same as us
try:
last_section = open_sections.pop()
except IndexError as e:
raise ChevronError(
f'Trying to close tag "{tag_key}"\n'
"Looks like it was not opened.\n"
f"line {_CURRENT_LINE + 1}"
) from e
if tag_key != last_section:
# Otherwise we need to complain
raise ChevronError(
f'Trying to close tag "{tag_key}"\n'
f'last open tag is "{last_section}"\n'
f"line {_CURRENT_LINE + 1}"
)
# Do the second check to see if we're a standalone
is_standalone = r_sa_check(template, tag_type, is_standalone)
# Which if we are
if is_standalone:
# Remove the stuff before the newline
template = template.split("\n", 1)[-1]
# Partials need to keep the spaces on their left
if tag_type != "partial":
# But other tags don't
literal = literal.rstrip(" ")
# Start yielding
# Ignore literals that are empty
if literal != "":
yield ("literal", literal)
# Ignore comments and set delimiters
if tag_type not in ["comment", "set delimiter?"]:
yield (tag_type, tag_key)
# If there are any open sections when we're done
if open_sections:
# Then we need to complain
raise ChevronError(
"Unexpected EOF\n"
f'the tag "{open_sections[-1]}" was never closed\n'
f"was opened at line {_LAST_TAG_LINE}"
)
#
# Helper functions
#
def _html_escape(string: str) -> str:
"""HTML escape all of these " & < >"""
html_codes = {
'"': """,
"<": "<",
">": ">",
}
# & must be handled first
string = string.replace("&", "&")
for char in html_codes:
string = string.replace(char, html_codes[char])
return string
def _get_key(
key: str,
scopes: Scopes,
warn: bool,
keep: bool,
def_ldel: str,
def_rdel: str,
) -> Any:
"""Get a key from the current scope"""
# If the key is a dot
if key == ".":
# Then just return the current scope
return scopes[0]
# Loop through the scopes
for scope in scopes:
try:
# Return an empty string if falsy, with two exceptions
# 0 should return 0, and False should return False
if scope in (0, False):
return scope
# For every dot separated key
for child in key.split("."):
# Return an empty string if falsy, with two exceptions
# 0 should return 0, and False should return False
if scope in (0, False):
return scope
# Move into the scope
try:
# Try subscripting (Normal dictionaries)
scope = cast(Dict[str, Any], scope)[child]
except (TypeError, AttributeError):
try:
scope = getattr(scope, child)
except (TypeError, AttributeError):
# Try as a list
scope = scope[int(child)] # type: ignore
try:
# This allows for custom falsy data types
# https://github.com/noahmorrison/chevron/issues/35
if scope._CHEVRON_return_scope_when_falsy: # type: ignore
return scope
except AttributeError:
if scope in (0, False):
return scope
return scope or ""
except (AttributeError, KeyError, IndexError, ValueError):
# We couldn't find the key in the current scope
# We'll try again on the next pass
pass
# We couldn't find the key in any of the scopes
if warn:
logger.warn(f"Could not find key '{key}'")
if keep:
return f"{def_ldel} {key} {def_rdel}"
return ""
def _get_partial(name: str, partials_dict: Mapping[str, str]) -> str:
"""Load a partial"""
try:
# Maybe the partial is in the dictionary
return partials_dict[name]
except KeyError:
return ""
#
# The main rendering function
#
g_token_cache: Dict[str, List[Tuple[str, str]]] = {}
EMPTY_DICT: MappingProxyType[str, str] = MappingProxyType({})
[docs]def render(
template: Union[str, List[Tuple[str, str]]] = "",
data: Mapping[str, Any] = EMPTY_DICT,
partials_dict: Mapping[str, str] = EMPTY_DICT,
padding: str = "",
def_ldel: str = "{{",
def_rdel: str = "}}",
scopes: Optional[Scopes] = None,
warn: bool = False,
keep: bool = False,
) -> str:
"""Render a mustache template.
Renders a mustache template with a data scope and inline partial capability.
Arguments:
template -- A file-like object or a string containing the template.
data -- A python dictionary with your data scope.
partials_path -- The path to where your partials are stored.
If set to None, then partials won't be loaded from the file system
(defaults to '.').
partials_ext -- The extension that you want the parser to look for
(defaults to 'mustache').
partials_dict -- A python dictionary which will be search for partials
before the filesystem is. {'include': 'foo'} is the same
as a file called include.mustache
(defaults to {}).
padding -- This is for padding partials, and shouldn't be used
(but can be if you really want to).
def_ldel -- The default left delimiter
("{{" by default, as in spec compliant mustache).
def_rdel -- The default right delimiter
("}}" by default, as in spec compliant mustache).
scopes -- The list of scopes that get_key will look through.
warn -- Log a warning when a template substitution isn't found in the data
keep -- Keep unreplaced tags when a substitution isn't found in the data.
Returns:
A string containing the rendered template.
"""
# If the template is a sequence but not derived from a string
if isinstance(template, Sequence) and not isinstance(template, str):
# Then we don't need to tokenize it
# But it does need to be a generator
tokens: Iterator[Tuple[str, str]] = (token for token in template)
else:
if template in g_token_cache:
tokens = (token for token in g_token_cache[template])
else:
# Otherwise make a generator
tokens = tokenize(template, def_ldel, def_rdel)
output = ""
if scopes is None:
scopes = [data]
# Run through the tokens
for tag, key in tokens:
# Set the current scope
current_scope = scopes[0]
# If we're an end tag
if tag == "end":
# Pop out of the latest scope
del scopes[0]
# If the current scope is falsy and not the only scope
elif not current_scope and len(scopes) != 1:
if tag in ["section", "inverted section"]:
# Set the most recent scope to a falsy value
scopes.insert(0, False)
# If we're a literal tag
elif tag == "literal":
# Add padding to the key and add it to the output
output += key.replace("\n", "\n" + padding)
# If we're a variable tag
elif tag == "variable":
# Add the html escaped key to the output
thing = _get_key(
key, scopes, warn=warn, keep=keep, def_ldel=def_ldel, def_rdel=def_rdel
)
if thing is True and key == ".":
# if we've coerced into a boolean by accident
# (inverted tags do this)
# then get the un-coerced object (next in the stack)
thing = scopes[1]
if not isinstance(thing, str):
thing = str(thing)
output += _html_escape(thing)
# If we're a no html escape tag
elif tag == "no escape":
# Just lookup the key and add it
thing = _get_key(
key, scopes, warn=warn, keep=keep, def_ldel=def_ldel, def_rdel=def_rdel
)
if not isinstance(thing, str):
thing = str(thing)
output += thing
# If we're a section tag
elif tag == "section":
# Get the sections scope
scope = _get_key(
key, scopes, warn=warn, keep=keep, def_ldel=def_ldel, def_rdel=def_rdel
)
# If the scope is a callable (as described in
# https://mustache.github.io/mustache.5.html)
if callable(scope):
# Generate template text from tags
text = ""
tags: List[Tuple[str, str]] = []
for token in tokens:
if token == ("end", key):
break
tags.append(token)
tag_type, tag_key = token
if tag_type == "literal":
text += tag_key
elif tag_type == "no escape":
text += f"{def_ldel}& {tag_key} {def_rdel}"
else:
text += "{}{} {}{}".format(
def_ldel,
{
"comment": "!",
"section": "#",
"inverted section": "^",
"end": "/",
"partial": ">",
"set delimiter": "=",
"no escape": "&",
"variable": "",
}[tag_type],
tag_key,
def_rdel,
)
g_token_cache[text] = tags
rend = scope(
text,
lambda template, data=None: render(
template,
data={},
partials_dict=partials_dict,
padding=padding,
def_ldel=def_ldel,
def_rdel=def_rdel,
scopes=data and [data] + scopes or scopes,
warn=warn,
keep=keep,
),
)
output += rend
# If the scope is a sequence, an iterator or generator but not
# derived from a string
elif isinstance(scope, (Sequence, Iterator)) and not isinstance(scope, str):
# Then we need to do some looping
# Gather up all the tags inside the section
# (And don't be tricked by nested end tags with the same key)
# TODO: This feels like it still has edge cases, no?
tags = []
tags_with_same_key = 0
for token in tokens:
if token == ("section", key):
tags_with_same_key += 1
if token == ("end", key):
tags_with_same_key -= 1
if tags_with_same_key < 0:
break
tags.append(token)
# For every item in the scope
for thing in scope:
# Append it as the most recent scope and render
new_scope = [thing] + scopes
rend = render(
template=tags,
scopes=new_scope,
padding=padding,
partials_dict=partials_dict,
def_ldel=def_ldel,
def_rdel=def_rdel,
warn=warn,
keep=keep,
)
output += rend
else:
# Otherwise we're just a scope section
scopes.insert(0, scope)
# If we're an inverted section
elif tag == "inverted section":
# Add the flipped scope to the scopes
scope = _get_key(
key, scopes, warn=warn, keep=keep, def_ldel=def_ldel, def_rdel=def_rdel
)
scopes.insert(0, cast(Literal[False], not scope))
# If we're a partial
elif tag == "partial":
# Load the partial
partial = _get_partial(key, partials_dict)
# Find what to pad the partial with
left = output.rpartition("\n")[2]
part_padding = padding
if left.isspace():
part_padding += left
# Render the partial
part_out = render(
template=partial,
partials_dict=partials_dict,
def_ldel=def_ldel,
def_rdel=def_rdel,
padding=part_padding,
scopes=scopes,
warn=warn,
keep=keep,
)
# If the partial was indented
if left.isspace():
# then remove the spaces from the end
part_out = part_out.rstrip(" \t")
# Add the partials output to the output
output += part_out
return output
