# compile.py - Syntax driven compilation support for DHParser
#
# Copyright 2016 by Eckhart Arnold (arnold@badw.de)
# Bavarian Academy of Sciences an Humanities (badw.de)
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied. See the License for the specific language governing
# permissions and limitations under the License.
"""
Module ``compile`` contains a skeleton class for syntax
driven compilation support. Class ``Compiler`` can serve as base
class for a compiler. Compiler objects
are callable an receive the Abstract syntax tree (AST)
as argument and yield whatever output the compiler produces. In
most Digital Humanities applications this will be
XML-code. However, it can also be anything else, like binary
code or, as in the case of DHParser's EBNF-compiler, Python
source code.
Function ``compile_source`` invokes all stages of the compilation
process, i.e. pre-processing, parsing, CST to AST-transformation
and compilation.
See module ``ebnf`` for a sample of the implementation of a
compiler object.
"""
from collections import namedtuple
import copy
import functools
import os
import traceback
from typing import Any, Optional, Tuple, List, Set, Dict, Union, Callable, cast
from DHParser.configuration import get_config_value
from DHParser.preprocess import PreprocessorFunc
from DHParser.nodetree import Node, RootNode, EMPTY_PTYPE, Trail
from DHParser.transform import TransformerCallable
from DHParser.parse import Grammar
from DHParser.preprocess import gen_neutral_srcmap_func
from DHParser.error import is_error, is_fatal, Error, FATAL, \
TREE_PROCESSING_CRASH, COMPILER_CRASH, AST_TRANSFORM_CRASH, has_errors
from DHParser.log import log_parsing_history, log_ST, is_logging
from DHParser.toolkit import load_if_file, is_filename, re
__all__ = ('CompilerError',
'Compiler',
'CompilerCallable',
'CompilerFactory',
'CompilationResult',
'process_tree',
'run_pipeline',
'compile_source',
'visitor_name',
'attr_visitor_name')
[docs]class CompilerError(Exception):
"""
Exception raised when an error of the compiler itself is detected.
Compiler errors are not to be confused with errors in the source
code to be compiled, which do not raise Exceptions but are merely
reported as an error.
"""
pass
[docs]def visitor_name(node_name: str) -> str:
"""
Returns the visitor_method name for `name`, e.g.::
>>> visitor_name('expression')
'on_expression'
>>> visitor_name('!--')
'on_212d2d'
"""
if re.match(r'\w+$', node_name):
return 'on_' + node_name
else:
letters = []
for ch in node_name:
if not re.match(r'\w', ch):
ch = hex(ord(ch))[2:]
letters.append(ch)
return 'on_' + ''.join(letters)
[docs]def attr_visitor_name(attr_name: str) -> str:
"""
Returns the visitor_method name for `attr_name`, e.g.::
>>> attr_visitor_name('class')
'attr_class'
"""
return 'attr_' + attr_name
ROOTNODE_PLACEHOLDER = RootNode()
CompilerFunc = Callable[[Node], Any]
[docs]class Compiler:
"""
Class Compiler is the abstract base class for compilers. Compiler
objects are callable and take the root node of the abstract
syntax tree (AST) as argument and return the compiled code in a
format chosen by the compiler itself.
Subclasses implementing a compiler must define `on_XXX()`-methods
for each node name that can occur in the AST where 'XXX' is the
node's name(for unnamed nodes it is the node's ptype without the
leading colon ':').
These compiler methods take the node on which they are run as
argument. Other than in the AST transformation, which runs depth-first,
compiler methods are called forward moving starting with the root
node, and they are responsible for compiling the child nodes
themselves. This should be done by invoking the `compile(node)`-
method which will pick the right `on_XXX`-method. It is not
recommended to call the `on_XXX`-methods directly.
Variables that are (re-)set only in the constructor and retain their
value if changed during subesquent calls::
:ivar forbid_returning_None: Default value: True. Most of the time,
if a compiler-method (i.e. on_XXX()) returns None, this is
a mistake due to a forgotten return statement. The method
compile() checks for this mistake and raises an error if
a compiler-method returns None. However, some compilers require
the possibility to return None-values. In this case
``forbis_returing_None`` should be set to False in the constructor
of the derived class.
(Another Alternativ would be to return a sentinel object instead of
None.)
Object-Variables that are reset after each call of the Compiler-object::
:ivar trail: A list of parent nodes that ends with the currently
compiled node.
:ivar tree: The root of the abstract syntax tree.
:ivar finalizers: A stack of tuples (function, parameters) that will be
called in reverse order after compilation.
:ivar has_attribute_visitors: A flag indicating that the class has
attribute-visitor-methods which are named 'attr_ATTRIBUTENAME'
and will be called if the currently processed node has one
or more attributes for which such visitors exist.
:ivar _dirty_flag: A flag indicating that the compiler has already been
called at least once and that therefore all compilation
variables must be reset when it is called again.
:ivar _debug: A flag indicating that debugging is turned on. The value
for this flag is read before each call of the configuration
(see debugging section in DHParser.configuration).
If debugging is turned on the compiler class raises en
error if there is an attempt to be compile one and the same
node a second time..
:ivar _debug_already_compiled: A set of nodes that have already been compiled.
"""
def __init__(self):
self.has_attribute_visitors = any(field[0:5] == 'attr_' and callable(getattr(self, field))
for field in dir(self))
self.forbid_returning_None = True # type: bool
self.reset()
[docs] def reset(self):
"""
Resets alls variables to their default values before the next call
of the object.
"""
self.tree = ROOTNODE_PLACEHOLDER # type: RootNode
self.trail = [] # type: Trail
self._dirty_flag = False
self._debug = get_config_value('debug_compiler') # type: bool
self._debug_already_compiled = set() # type: Set[Node]
self.finalizers = [] # type: List[Tuple[Callable, Tuple]]
self.method_dict = {} # type: Dict[str, CompilerFunc]
[docs] def prepare(self, root: Node) -> None:
"""
A preparation method that will be called after everything else has
been initialized and immediately before compilation starts. This method
can be overwritten in order to implement preparation tasks.
"""
pass
[docs] def finalize(self, result: Any) -> Any:
"""
A finalization method that is called after compilation has finished and
after all tasks from the finalizers-stack have been executed
"""
return result
def __call__(self, root: Node) -> Any:
"""
Compiles the abstract syntax tree with the root node `node` and
returns the compiled code. It is up to subclasses implementing
the compiler to determine the format of the returned data.
(This very much depends on the kind and purpose of the
implemented compiler.)
The ``__call__``-method is also responsible for initializations
required before the compilation and the finalization the compilation
has been finished by taking the following steps::
1. reset all variables and initialize ``self.tree`` with ``root``
2. call the :py:meth:`Compiler.prepare()`-method.
3. compile the syntax-tree originating in ``root`` by calling
:py:meth:`Compiler.compile()` on the root-node.
4. call all finalizers in the ``self.finalizers``-list.
5. call the :py:meth:`Compiler.finalize()`-method.
:param root: The root-node of the syntax tree to be compiled. ``root``
does not need to be of type :py:class:`~nodetree.RootNode` in order
to allow compiling parts of a syntax tree.
:returns: The resulting object of the compilation.
"""
if self._dirty_flag:
self.reset()
self._dirty_flag = True
self.tree = cast(RootNode, root) if isinstance(root, RootNode) else RootNode(root)
self.prepare(root)
result = self.compile(root)
while self.finalizers:
task, parameters = self.finalizers.pop()
task(*parameters)
result = self.finalize(result)
return result
def visit_attributes(self, node) -> Node:
if node.has_attr():
self.trail.append(node)
for attribute, value in list(node.attr.items()):
try:
attribute_visitor = self.__getattribute__(attr_visitor_name(attribute))
node = attribute_visitor(node, value) or node
except AttributeError:
pass
self.trail.pop()
return node
[docs] def fallback_compiler(self, node: Node) -> Any:
"""This is a generic compiler function which will be called on
all those node types for which no compiler method `on_XXX` has
been defined."""
replacements = {} # type: Dict[int, Node]
if node.children:
for child in node.children:
nd = self.compile(child)
if id(nd) != id(child):
replacements[id(child)] = nd
if nd is not None and not isinstance(nd, Node):
tn = node.name
raise TypeError(
'Fallback compiler for Node `%s` received a value of type '
'`%s` from child `%s` instead of the required return type `Node`. '
'Override `DHParser.compile.Compiler.fallback_compiler()` or add '
'method `on_%s(self, node)` in class `%s` to avoid this error!'
% (tn, str(type(nd)), child.name, tn, self.__class__.__name__))
if replacements:
# replace Nodes the identity of which has been changed during transformation
# and drop any returned None-results
result = []
for child in node.children:
nd = replacements.get(id(child), child)
if nd is not None and nd.name != EMPTY_PTYPE:
result.append(nd)
node.result = tuple(result)
if self.has_attribute_visitors:
node = self.visit_attributes(node)
return node
def find_compilation_method(self, node_name: str) -> CompilerFunc:
try:
method = self.method_dict[node_name]
except KeyError:
method_name = visitor_name(node_name)
try:
method = self.__getattribute__(method_name)
except AttributeError:
method = self.fallback_compiler
self.method_dict[node_name] = method
return method
[docs] def compile(self, node: Node) -> Any:
"""
Calls the compilation method for the given node and returns the
result of the compilation.
The method's name is derived from either the node's parser
name or, if the parser is disposable, the node's parser's class
name by adding the prefix ``on_``.
Note that ``compile`` does not call any compilation functions
for the parsers of the sub nodes by itself. Rather, this should
be done within the compilation methods.
"""
if self._debug:
assert node not in self._debug_already_compiled
self._debug_already_compiled.add(node)
elem = node.name
if elem[:1] == ':':
elem = elem[1:] + '__'
compiler = self.find_compilation_method(elem)
self.trail.append(node)
result = compiler(node)
self.trail.pop()
if self.has_attribute_visitors:
node = self.visit_attributes(node)
if result is None and self.forbid_returning_None:
raise CompilerError(
('Method on_%s returned `None` instead of a valid compilation '
'result! It is recommended to use `nodetree.EMPTY_NODE` as a '
'void value. This Error can be turn off by adding '
'`self.forbid_returning_None = False` to the reset()-Method of your'
'compiler class, in case on_%s actually SHOULD be allowed to '
'return None.') % (elem, elem))
return result
def logfile_basename(filename_or_text, function_or_class_or_instance) -> str:
"""Generates a reasonable logfile-name (without extension) based on
the given information.
"""
if is_filename(filename_or_text):
return os.path.basename(os.path.splitext(filename_or_text)[0])
else:
try:
name = function_or_class_or_instance.__qualname__
except AttributeError:
name = function_or_class_or_instance.__class__.__name__
i = name.find('.')
return name[:i] + '_out' if i >= 0 else name
# processing pipeline support #########################################
CompilerCallable = Union[Compiler, Callable[[RootNode], Any], functools.partial]
CompilerFactory = Union[Callable[[], CompilerCallable], functools.partial]
def filter_stacktrace(stacktrace: List[str]) -> List[str]:
"""Removes those frames from a formatted stacktrace that are located
within the DHParser-code."""
n = 0
for n, frame in enumerate(stacktrace):
i = frame.find('"')
k = frame.find('"', i + 1)
if frame.find("DHParser", i, k) < 0:
break
return stacktrace[n:]
[docs]def process_tree(tp: CompilerCallable, tree: RootNode) -> Any:
"""Process a tree with the tree-processor `tp` only if no fatal error
has occurred so far. Catch any Python-exceptions in case
any normal errors have occurred earlier in the processing pipeline.
Don't catch Python-exceptions if no errors have occurred earlier.
This behaviour is based on the assumption that given any non-fatal
errors have occurred earlier, the tree passed through the pipeline
might not be in a state that is expected by the later stages, thus if
an exception occurs it is not really to be considered a programming
error. Processing stages should be written with possible errors
occurring in earlier stages in mind, though. However, because it could
be difficult to provide for all possible kinds of badly structured
trees resulting from errors, exceptions occurring when processing
potentially faulty trees will be dealt with gracefully.
Tree processing should generally be assumed to change the tree
in place. If the input tree shall be preserved, it is necessary to
make a deep copy of the input tree, before calling process_tree.
"""
assert isinstance(tree, RootNode)
result = None
if not is_fatal(tree.error_flag):
if is_error(tree.error_flag):
# assume Python crashes are merely a consequence of earlier
# errors, so let's catch them
try:
result = tp(tree)
except Exception as e:
# node = tp.trail[-1] if hasattr(tp, 'trail') and tp.trail else tree
node = getattr(tp, 'trail', [tree])[-1]
st = traceback.format_list(traceback.extract_tb(e.__traceback__))
trace = ''.join(st) # filter_stacktrace(st)
tree.new_error(
node, "Tree-processing failed, most likely, due to errors earlier in "
"in the processing pipeline. Crash Message: %s: %s\n%s"
% (e.__class__.__name__, str(e), trace),
TREE_PROCESSING_CRASH)
else:
# assume Python crashes are programming mistakes, so let
# the exceptions through
result = tp(tree)
return result
Junction = Tuple[str, CompilerFactory, str]
[docs]def run_pipeline(junctions: Set[Junction],
source_stages: Dict[str, RootNode],
target_stages: Set[str]) -> Dict[str, Tuple[Any, List[Error]]]:
"""
Runs all the intermediary compilation-steps that are necessary to produce
the "target-stages" from the given "source-stages". Here, each source-stage
consists of a name for that stage, say "AST", and a node-tree that
represents the data at this stage of the processing pipeline. In the
target-stage, the data can be a node-tree or data of any other kind.
The stages or connected through chains of junctions, where a junction is
essentially a function that transforms a tree from one particular stage
(identified by its name) to another stage, again itentified by its name.
TODO: Parallelize processing of junctions
"""
t_to_j = {j[-1]: j for j in junctions}
steps = []
targets = target_stages.copy()
already_reached = targets.copy() | source_stages.keys()
while targets:
try:
steps.append([t_to_j[t] for t in targets if t not in source_stages])
except KeyError as e:
raise AssertionError(f"{e.args[0]} is not a valid target.")
targets = {j[0] for j in steps[-1] if j[0] not in already_reached}
already_reached |= targets
for step in steps[:-1]:
for j in steps[-1]:
try:
step.remove(j)
except ValueError:
pass
if not (target_stages <= already_reached):
raise ValueError(f'Target-stages: {target_stages - already_reached} '
f'cannot be reached with junctions: {junctions}.')
sources = [j[0] for step in steps for j in step]
disposables = {s for s in set(sources) if s not in target_stages and sources.count(s) <= 1}
steps.reverse()
results: Dict[str, Any] = source_stages.copy()
errata: Dict[str, List[Error]] = {s: source_stages[s].errors_sorted for s in source_stages}
for step in steps:
for junction in step:
t = junction[-1]
if t not in results:
s = junction[0]
tree = results[s] if s in disposables else copy.deepcopy(results[s])
if s not in target_stages:
sources.remove(s)
if sources.count(s) <= 1:
disposables.add(s)
if tree is None:
results[t] = None
errata[t] = []
else:
if not isinstance(tree, RootNode):
raise ValueError(f'Object in stage {s} is not a tree but a {type(tree)} '
f'and, therefore, cannot be processed to {t}')
results[t] = process_tree(junction[1](), tree)
errata[t] = copy.copy(tree.errors_sorted)
return {t: (results[t], errata[t]) for t in target_stages}
CompilationResult = namedtuple('CompilationResult',
['result', # type: Optional[Any]
'messages', # type: List[Error]
'AST'], # type: Optional[RootNode]
module=__name__)
[docs]def compile_source(source: str,
preprocessor: Optional[PreprocessorFunc],
parser: Grammar,
transformer: TransformerCallable,
compiler: CompilerCallable,
*, preserve_AST: bool = False) -> CompilationResult:
"""Compiles a source in four stages:
1. Pre-Processing (if needed)
2. Parsing
3. AST-transformation
4. Compiling.
The later stages AST-transformation, compilation will only be invoked if
no fatal errors occurred in any of the earlier stages of the processing
pipeline.
:param source: The input text for compilation or a the name of a
file containing the input text.
:param preprocessor: text -> text. A preprocessor function
or None, if no preprocessor is needed.
:param parser: A parsing function or grammar class
:param transformer: A transformation function that takes
the root-node of the concrete syntax tree as an argument and
transforms it (in place) into an abstract syntax tree.
:param compiler: A compiler function or compiler class
instance
:param preserve_AST: Preserves the AST-tree.
:returns: The result of the compilation as a 3-tuple
(result, errors, abstract syntax tree). In detail:
1. The result as returned by the compiler or ``None`` in case of failure
2. A list of error or warning messages
3. The root-node of the abstract syntax tree if `preserve_ast` is True
or `None` otherwise.
"""
ast = None # type: Optional[Node]
try:
original_text = load_if_file(source) # type: str
except (FileNotFoundError, IOError) as e:
return CompilationResult(None, [Error(str(e), 0, COMPILER_CRASH)], None)
source_name = source if is_filename(source) else ''
log_file_name = logfile_basename(source, compiler) if is_logging() else '' # type: str
if not hasattr(parser, 'free_char_parsefunc__') or parser.history_tracking__:
# log only for custom parser/transformer/compilers
log_syntax_trees = get_config_value('log_syntax_trees')
else:
log_syntax_trees = set()
# preprocessing
errors = []
if preprocessor is None:
source_text = original_text # type: str
source_mapping = gen_neutral_srcmap_func(source_text, source_name)
# lambda i: SourceLocation(source_name, 0, i) # type: SourceMapFunc
else:
_, source_text, source_mapping, errors = preprocessor(original_text, source_name)
if has_errors(errors, FATAL):
return CompilationResult(None, errors, None)
# parsing
syntax_tree = parser(source_text, source_mapping=source_mapping) # type: RootNode
for e in errors: syntax_tree.add_error(None, e)
syntax_tree.source = original_text
syntax_tree.source_mapping = source_mapping
if 'cst' in log_syntax_trees:
log_ST(syntax_tree, log_file_name + '.cst')
if parser.history_tracking__:
log_parsing_history(parser, log_file_name)
# assert is_error(syntax_tree.error_flag) or str(syntax_tree) == strip_tokens(source_text), \
# str(syntax_tree) # Ony valid if neither tokens or whitespace are dropped early
result = None
if not is_fatal(syntax_tree.error_flag):
# AST-transformation
if is_error(syntax_tree.error_flag):
# catch Python exception, because if an error has occurred
# earlier, the syntax tree might not look like expected,
# which could (fatally) break AST transformations.
try:
transformer(syntax_tree)
except Exception as e:
syntax_tree.new_error(syntax_tree,
"AST-Transformation failed due to earlier parser errors. "
"Crash Message: %s: %s" % (e.__class__.__name__, str(e)),
AST_TRANSFORM_CRASH)
else:
transformer(syntax_tree)
if 'ast' in log_syntax_trees:
log_ST(syntax_tree, log_file_name + '.ast')
if not is_fatal(syntax_tree.error_flag):
if preserve_AST:
ast = copy.deepcopy(syntax_tree)
# Compilation
result = process_tree(compiler, syntax_tree)
messages = syntax_tree.errors_sorted # type: List[Error]
# Obsolete, because RootNode adjusts error locations whenever an error is added:
# adjust_error_locations(messages, original_text, source_mapping)
return CompilationResult(result, messages, ast)
# TODO: Verify compiler against grammar,
# i.e. make sure that for all on_X()-methods, `X` is the name of a parser
# Does that make sense? Tag names could change during AST-Transformation!
# TODO: AST validation against an ASDL-Specification