178 lines
8.0 KiB
Python
178 lines
8.0 KiB
Python
# -*- coding: utf-8; -*-
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"""Utilities related to writing macro expanders and similar meta-metaprogramming tasks."""
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__all__ = ["resolve_package", "relativize", "match_syspath",
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"ismacroimport", "get_macros"]
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from ast import ImportFrom
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import importlib
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import importlib.util
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import os
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import pathlib
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import sys
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from .unparser import unparse_with_fallbacks
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from .utils import format_location
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def resolve_package(filename): # TODO: for now, `guess_package`, really. Check the docs again.
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"""Resolve absolute Python package name for .py source file `filename`.
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If `filename` is at the top level of the matching entry in `sys.path`, raises `ImportError`.
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If `filename` is not under any directory in `sys.path`, raises `ValueError`.
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"""
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containing_directory = pathlib.Path(filename).expanduser().resolve().parent
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root_path, relative_path = relativize(containing_directory)
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if not relative_path: # at the root_path - not inside a package
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absolute_filename = str(pathlib.Path(filename).expanduser().resolve())
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resolved = f" (resolved to {absolute_filename})" if absolute_filename != str(filename) else ""
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raise ImportError(f"{filename}{resolved} is not in a package, but at the root level of syspath {str(root_path)}")
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package_dotted_name = relative_path.replace(os.path.sep, ".")
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return package_dotted_name
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def relativize(filename):
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"""Convert `filename` into a relative one under the matching `sys.path`.
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Return value is `(root_path, relative_path)`, where `root_path` is the
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return value of `match_syspath` (a `pathlib.Path`), and `relative_path`
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is a string containing the relative path of `filename` under `root_path`.
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`filename` can be a .py source file or a package directory.
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"""
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absolute_filename = str(pathlib.Path(filename).expanduser().resolve())
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root_path = match_syspath(absolute_filename)
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relative_path = absolute_filename[len(str(root_path)):]
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if relative_path.startswith(os.path.sep):
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relative_path = relative_path[len(os.path.sep):]
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return root_path, relative_path
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def match_syspath(filename):
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"""Return the entry in `sys.path` the `filename` is found under.
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Return value is a `pathlib.Path` for the matching `sys.path` directory,
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resolved to an absolute directory.
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If `filename` is not under any directory in `sys.path`, raises `ValueError`.
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"""
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absolute_filename = str(pathlib.Path(filename).expanduser().resolve())
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# Match deeper paths first; for readability, break ties lexicographically.
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# This allows the matching to work also if e.g. both `/home/user/.local/`
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# and `/home/user/.local/lib/python3.8/site-packages/` end up on `sys.path`.
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def sortkey(s):
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return -s.count(os.path.sep), s
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for root_path in sorted(sys.path, key=sortkey):
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root_path = pathlib.Path(root_path).expanduser().resolve()
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if absolute_filename.startswith(str(root_path)):
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return root_path
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resolved = f" (resolved to {absolute_filename})" if absolute_filename != str(filename) else ""
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raise ValueError(f"{filename}{resolved} not under any directory in `sys.path`")
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# --------------------------------------------------------------------------------
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def ismacroimport(statement, magicname='macros'):
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"""Return whether `statement` is a macro-import.
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A macro-import is a statement of the form::
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from ... import macros, ...
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where "macros" is the literal string given as `magicname`.
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"""
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if isinstance(statement, ImportFrom):
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firstimport = statement.names[0]
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if firstimport.name == magicname and firstimport.asname is None:
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return True
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return False
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def get_macros(macroimport, *, filename, reload=False, allow_asname=True, self_module=None):
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"""Get absolute module name, macro names and macro functions from a macro-import.
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As a side effect, import the macro definition module.
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Return value is `module_absname, {macroname0: macrofunction0, ...}`.
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`filename` is the full path to the `.py` being macroexpanded, for resolving
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relative macro-imports and for error reporting. In interactive use, can be
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an arbitrary label.
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Use the `reload` flag only when implementing a REPL, because it'll refresh modules,
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causing different uses of the same macros to point to different function objects.
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Use `allow_asname` to say whether your expander supports renaming macros
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at the use site. Usually it's a good idea to support it; but e.g. renaming a
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dialect makes no sense.
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`self_module` is an optional string, the absolute dotted module name of the
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module being expanded. Used for supporting `from __self__ import macros, ...`
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for multi-phase compilation (a.k.a. staging).
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This function is meant for implementing actual macro expanders.
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"""
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package_absname = None
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if macroimport.level and filename.endswith(".py"):
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try:
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package_absname = resolve_package(filename)
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except (ValueError, ImportError) as err:
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raise ImportError(f"while resolving absolute package name of {filename}, which uses relative macro-imports") from err
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if macroimport.module is None:
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# fallbacks may trigger if the macro-import is programmatically generated.
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approx_sourcecode = unparse_with_fallbacks(macroimport, debug=True, color=True)
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loc = format_location(filename, macroimport, approx_sourcecode)
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raise SyntaxError(f"{loc}\nmissing module name in macro-import")
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# macro-import from an earlier phase of a module using `with phase`
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if macroimport.module == "__self__":
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if macroimport.level:
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approx_sourcecode = unparse_with_fallbacks(macroimport, debug=True, color=True)
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loc = format_location(filename, macroimport, approx_sourcecode)
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raise SyntaxError(f"{loc}\nself-macro-imports cannot be relative")
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# When we get here, the module, as compiled up to the previous phase,
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# is already in `sys.modules`, because the importer temporarily places
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# it there. That way we can load macro bindings from it, while the
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# current phase is being compiled.
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#
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# If the highest phase tries to self-macro-import (which is incorrect),
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# a blank dummy module will have been placed in `sys.modules` by Python's
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# import system itself. So this should never trigger a `KeyError`;
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# it'll instead trigger an error when attempting to import a name
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# from that blank module.
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#
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# But just in case that some exotic use case leads to a `KeyError` here,
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# translate that to an error sensible at this level of abstraction.
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module_absname = self_module
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try:
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module = sys.modules[module_absname]
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except KeyError:
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raise ModuleNotFoundError(f"{loc}\nModule {module_absname} not found in `sys.modules`")
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# regular macro-import
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else:
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module_absname = importlib.util.resolve_name("." * macroimport.level + macroimport.module, package_absname)
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try:
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module = importlib.import_module(module_absname)
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except ModuleNotFoundError as err:
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approx_sourcecode = unparse_with_fallbacks(macroimport, debug=True, color=True)
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loc = format_location(filename, macroimport, approx_sourcecode)
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raise ModuleNotFoundError(f"{loc}\nNo module named {module_absname}") from err
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if reload:
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module = importlib.reload(module)
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bindings = {}
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for name in macroimport.names[1:]:
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if not allow_asname and name.asname is not None:
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raise ImportError(f"{loc}\nThis expander (see traceback) does not support as-naming macro-imports.")
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try:
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bindings[name.asname or name.name] = getattr(module, name.name)
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except AttributeError as err:
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approx_sourcecode = unparse_with_fallbacks(macroimport, debug=True, color=True)
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loc = format_location(filename, macroimport, approx_sourcecode)
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raise ImportError(f"{loc}\ncannot import name '{name.name}' from module {module_absname}") from err
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return module_absname, bindings
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