Version 3.3.0

3.3.0 (29 April 2021) - Captain Debughook edition:

New:

• Debug hook added to mcpyrate.core.BaseMacroExpander to see what the macro expander is doing. The step_expansion macro now uses it (which see for usage), but you can also hook your own functions to it.

• Public function mcpyrate.quotes.is_captured_value for advanced macrology. This allows your own macros to detect expansions of q[h[somename]] in the AST, and grab somename (original name, no name mangling) as well as the corresponding value. (There is also is_captured_macro, but the use cases of that are much more limited.) Detailed explanation in docstrings for now. Usage examples in the tests for the quotes module.

• mcpyrate.walkers.ASTTransformer and ASTVisitor now have a method generic_withstate, to temporarily replace the state when visiting the direct children of the given node. (This is a closer equivalent for macropy's set_ctx, sometimes useful for writing custom walkers.)

• Improve documentation on creating magic variables: add another major strategy, and explain both strategies in more detail.

Changed:

• step_expansion and stepr now accept the string "detailed" as a macro argument (in addition to the earlier "dump" that selects the AST dump renderer).

  When "detailed" is given, they will report every macro expansion using the debug hook. This facilitates debugging of macros that expand inside-out (using explicit recursion). The definition of step remains the same: the step counter is incremented whenever the debug stepper gets control back. Just as previously, inside-out expansion therefore occurs within one step, but now you can see the subtree of each inner macro invocation just before and after that macro expands.

  In block mode with step_expansion, one complete step is defined as expanding each statement in the suite by one step.

  The macro arguments for step_expansion and stepr can be passed in any order.

Fixed:

• Fix subscript slice handling in unparser for Python 3.9 and later. Now that ast.Index and ast.ExtSlice are gone, an ast.Tuple may appear directly in the slice position, representing multi-dimensional indexing. Such a tuple must be rendered without surrounding parentheses, because the notation a[1,2:5] is fine, but a[(1,2:5)] is a syntax error. See https://bugs.python.org/issue34822

• Fix bug in quasiquoting of constants: support also ... (the Ellipsis singleton).

• Fix bug in splice_ast_literals (a.k.a. run-time part of q) that made it crash on ast.Nonlocal and ast.Global nodes.

• Fix bug in type preservation of empty list in ASTTransformer.

• Fix bug in copy support of ASTMarker objects. Now it is possible to deepcopy ASTs that contain markers.

• Fix bug that caused the mcpyrate.debug.show_bindings macro or the REPL consoles to crash upon a specific kind of broken imports in user code. (E.g. accidentally binding a macro name to a module object instead of a function object.)

• Fix bug failing to honor possible overrides to sys.stderr in various debug-printing facilities. Always import sys and refer to sys.stderr to resolve the current value, never from sys import stderr.

• Up to Python 3.8, items in the decorator list cannot be subscripted, so decorator macros could not take macro arguments. In 3.9 this has been fixed, as implied by the grammar. To work around this issue in earlier supported Python versions (3.6, 3.7, 3.8), we now support parentheses as an alternative syntax for passing macro arguments, like in macropy. Note that macro arguments must in any case be passed positionally! (Reasons documented in the comments of mcpyrate.expander.)

Version 3.2.1

3.2.1 (10 April 2021)

• Fix version metadata in __init__.py.

3.2.0 (10 April 2021) - X marks the spot edition:

New:

• Documentation: the staging compiler is now documented.
• Documentation: contribution guidelines now include a section on automated tests.
• Add command-line option to macropython to delete bytecode caches:
  • Use macropython -c yourdirectory (equivalent: macropython --clean yourdirectory), where yourdirectory is a path (can be relative or absolute).
  • For a dry run, use macropython -c yourdirectory -n (equivalent: macropython --clean yourdirectory --dry-run), which just prints the full paths to the directories it would delete.
  • If you need programmatic access to this functionality, see mcpyrate.pycachecleaner.

Fixed:

• Fix #20, with thanks to @thirtythreeforty for reporting. mcpyrate should now support Python 3.9.
• Fix bug in mcpyrate.splicing.splice_expression. (Only affected that function; the expression mode of a[] uses a different code path.)
• Fix a crash in the generation of some error messages in mcpyrate.coreutils.get_macros. Particularly, the crash could occur if the module is not found in sys.modules, or if an as-import of a macro is attempted with a concrete expander type that doesn't support that feature.

v3.1.0

3.1.0 (12 February 2021) - Compiling on the high seas edition:

New:

• The mcpyrate compiler (implementing the import algorithm) is now exposed in mcpyrate.compiler for run-time use.

  • You can just expand, or both expand and compile code, as needed.
  • It is now convenient to compile and run macro-enabled quoted code snippets (or source code) at run time, see the functions mcpyrate.compiler.run and mcpyrate.compiler.create_module.
    • This makes it easier to test macros that are best tested via the behavior of the run-time code they output. (It also makes macro-enabled Python into a poor man's staged language [1] [2].)
    • The system allows dynamically creating modules (for executing code snippets in) at run time, as well as running code in the namespace of an existing module.
      • These features combine, so you can let run automatically create a module the first time, and then re-use that module if you want.
      • You can also create a module with a specific dotted name in sys.modules. The multi-phase compiler itself uses this feature.
    • Source code input supports dialects, macros, and multi-phase compilation. The source code represents a module.
    • Quoted AST input supports macros and multi-phase compilation. No source transforms for this kind of input, because the input is already an AST. (Dialect AST transformers and postprocessors should work.) The top level of the quoted block (i.e. the body of a with q as quoted:) is seen by the compiler as the top level of a module.
    • While the code snippet is running, the module's __file__ and __name__ attributes are available, as usual.
    • For extracting results into the surrounding context, just assign them to variables inside the code snippet. The top level of the code snippet is the module's top level. You have that module object available in the surrounding context (where you call run), so you can access those variables as its attributes.
  • Full documentation is in docstrings for now, see mcpyrate.compiler. Usage examples can be found in mcpyrate.test.test_compiler.

• Add support for PEP 582 - Python local packages directory in the macropython bootstrapper.

• The unparser now supports all three top-level node types, and supports also a list of AST nodes (e.g. a statement suite in an AST) as input.

• The StepExpansion dialect now works in AST-only mode, too.

  • It will enable DialectExpander debug mode in the source transform step, if that runs. If the AST transform step is reached and debug mode is still off, it will now enable debug mode at that time. Only one copy of the unprocessed code is printed regardless.

• README: add instructions to configure Emacs syntax highlighting.

• Add unpyrate.bunch.bunchify to convert an existing mapping instance into a Bunch.

Changed:

• Nested quasiquotes now work properly.

  Unquoting now only occurs when quote level hits zero. Inner quotes and unquotes are detected, for tracking the quote level, but are then left in the output as-is.

  Note as-is means "as unexpanded macro invocations". Because the quasiquote operators are just macros, and in macro-enabled Python, the tradition is that a function actually being a macro is a property of the use site, not of its definition site, it follows that there's no guarantee whether the quote operators are in the expander's bindings at any later time. Even if they are, there is no guarantee whether they still have the names they had at the time when the outermost quote expanded.

  What we have now is the result of taking the current design to its logical extreme. A better solution (for next-next-gen) may need a break from tradition, in that maybe a function being a macro should be a property of its definition site, not of its use site. Also, maybe the quasiquote operators should be considered core functionality, and not be renameable (like regular macros are).

  However, the current solution does give useful level separation that has real practical applications; see the dynamically generated module example in mcpyrate.test.test_compiler.

  This is not considered a breaking change, because the previous behavior of nested quasiquotes didn't make any sense, so nothing useful could be built on it.

Fixed:

• Fix INTI-CMNB/KiBot#29, with thanks to @skorokithakis and @set-soft.
• Fix #21, with thanks to @thirtythreeforty for reporting.
• Fix bug in unastify: drop the run-time part of q.
• Fix bug in rename: handle also module name in ImportFrom nodes.
• Fix SourceLocationInfoValidator.
• macropython now reports mcpyrate version separately from the version of the macropython script itself when run with the -v (--version) command-line option.

v3.0.1

3.0.1 (27 November 2020)

• Fix project metadata in setup.py.

3.0.0 (27 November 2020) - Arrr! edition:

Initial release of mcpyrate, the advanced, third-generation macro expander for Python, after the pioneering macropy, and the compact, pythonic mcpy. The emphasis is on correctness, feature-completeness for serious macro-enabled work, and simplicity, in that order.

We build on mcpy 2.0.0, but add a lot of new features.

New:

• Agile development tools.

  • Multi-phase compilation: Use macros also in the same module where they are defined.
  • Universal bootstrapper: macropython. Import and use macros in your main program.
  • Interactive console: macropython -i. Import, define and use macros in a console session.
    • Embeddable à la code.InteractiveConsole. See mcpyrate.repl.console.MacroConsole.
  • IPython extension mcpyrate.repl.iconsole. Import, define and use macros in an IPython session.
  • See full documentation of the REPL system.

• Testing and debugging.

  • Statement coverage is correctly reported by tools such as Coverage.py.
  • Macro expansion errors are reported at macro expansion time, with use site traceback.
  • Debug output with a step-by-step expansion breakdown. See macro mcpyrate.debug.step_expansion.
    • Has both expr and block modes. Use step_expansion[...] or with step_expansion as appropriate.
    • The output is syntax-highlighted, and line-numbered based on lineno fields from the AST.
      • Also names of macros currently bound in the expander are highlighted by step_expansion.
      • Line numbers are taken from statement AST nodes.
    • The invisible nodes ast.Module and ast.Expr are shown, since especially ast.Expr is a common trap for the unwary.
    • To step the expansion of a run-time AST value, see the macro mcpyrate.metatools.stepr.
  • Manual expand-once. See expander.visit_once; get the expander as a named argument of your macro. See also the expand1s and expand1r macros in mcpyrate.metatools.

• Lightning speed.

  • Bytecode caches (.pyc) are created and kept up-to-date. Saves macro expansion cost at startup for unchanged modules. Makes mcpyrate fast on average.

    Beside a .py source file itself, we look at any macro definition files
    it imports macros from, recursively, in a make-like fashion.

    The mtime is the latest of those of the source file and its macro-dependencies,
    considered recursively, so that if any macro definition anywhere in the
    macro-dependency tree of a source file is changed, Python will treat that
    source file as "changed", thus re-expanding and recompiling it (hence,
    updating the corresponding .pyc).

  • CAUTION: PEP 552 - Deterministic pycs is not supported; we support only the default mtime invalidation mode, at least for now.

• Quasiquotes, with advanced features.

  • Hygienically interpolate both regular values and macro names.
  • Delayed macro expansion inside quasiquoted code. User-controllable.
  • Inverse quasiquote operator. See function mcpyrate.quotes.unastify.
    • Convert a quasiquoted AST back into a direct AST, typically for further processing before re-quoting it.
      • Not an unquote; we have those too, but the purpose of unquotes is to interpolate values into quoted code. The inverse quasiquote, instead, undoes the quasiquote operation itself, after any unquotes have already been applied.
  • See full documentation of the quasiquote system.

• Macro arguments.

  • Opt-in. Declare by using the @parametricmacro decorator on your macro function.
  • Use brackets to invoke, e.g. macroname[arg0, ...][expr]. If no args, just leave that part out, e.g. macroname[expr].
  • The macroname[arg0, ...] syntax works in expr, block and decorator macro invocations in place of a bare macroname.
  • The named parameter args is a raw list of the macro argument ASTs. Empty if no args were sent, or if the macro function is not parametric.

• Identifier (a.k.a. name) macros.

  • Opt-in. Declare by using the @namemacro decorator on your macro function.
  • Can be used for creating magic variables that may only appear inside specific macro invocations.

• Dialects, i.e. whole-module source and AST transforms.

  • Think Racket's #lang, but for Python.
  • Define languages that use Python's surface syntax, but change the semantics; or plug in a per-module transpiler that (at import time) compiles source code from some other programming language into macro-enabled Python. Also an AST optimizer could be defined as a dialect. Dialects can be chained.
  • Sky's the limit, really. Until we get unpythonic ported to use mcpyrate, see pydialect for old example dialects.
  • For debugging, from mcpyrate.debug import dialects, StepExpansion.
  • If writing a full-module AST transformer that splices the whole module into a template, see mcpyrate.splicing.splice_dialect.
  • See full documentation of the dialect system.

• Conveniences.

  • Relative macro-imports (for code in packages), e.g. from .other import macros, kittify.
  • The expander automatically fixes missing ctx attributes in the AST, so you don't need to care about those in your macros.
  • In most cases, the expander also fills in correct source location information automatically (for coverage reporting). If you're discarding nodes from the input, then you may have to be slightly careful and use ast.copy_location appropriately.
  • Several block macros can be invoked in the same with (equivalent to nesting them, with leftmost outermost).
  • AST visitor and transformer à la macropy's Walker, to easily context-manage state for subtrees, and collect items across the whole walk. Full documentation.
  • AST markers (pseudo-nodes) for communication in a set of co-operating macros (and with the expander).
  • gensym to create a fresh, unused lexical identifier.
  • unparse to convert an AST to the corresponding source code, optionally with syntax highlighting (for terminal output).
  • dump to look at an AST representation directly, with (mostly) PEP8-compliant indentation, optionally with syntax highlighting (node types, field names, bare values).

v3.0.0

add PyPI install instructions