Source

say / say / show.py

"""Debugging print features. """

import string, inspect, sys, os, re, collections
from options import Options, OptionsContext
import linecache
from say.core import *
from say.linecacher import *
import ast
import codegen
from mementos import MementoMetaclass
import textwrap

def wrapped_if(value, prefix="", suffix="", transform=None):
    """
    If a string has a value, then transform it (optinally) and add the prefix and
    suffix. Else, return empty string. Handy for formatting operations, where
    one often wants to add decoration iff the value exists.
    """
    
    if not value:
        return ""
    s = transform(str(value)) if transform else str(value)
    return (prefix or "") + s + (suffix or "")

QUOTE_CHARS = ('"', "'", '"""')

def with_metaclass(meta, base=object):
    """Create a base class with a metaclass."""
    return meta("NewBase", (base,), {})

class CallArgs(with_metaclass(MementoMetaclass, ast.NodeVisitor)):
    """
    An ``ast.NodeVisitor`` that parses a Python function call and determines its
    arguments from the corresponding AST. Memoized so that parsing and
    traversing the AST is done once and only once; subseqnet requests are
    delivered via cache lookup.
    """

    TARGET_FUNCS = set(['show', 'show.items'])  # functions we care about

    def __init__(self, filepath, lineno):
        ast.NodeVisitor.__init__(self)
        self.filepath = filepath
        self.lineno   = lineno
        self.source   = None  # placeholder
        self.ast      = None  # placeholder
        self.args     = None  # placeholder
        self.get_ast()
        self.visit(self.ast)
    
    def get_ast(self):
        """
        Find the AST. Easy if single source line contains whole line. May
        need a bit of trial-and-error if over multiple lines.
        """
        src = ""
        for lastlineno in range(self.lineno, self.lineno+10):
            src += getline(self.filepath, lastlineno)
            try:
                srcleft = textwrap.dedent(src)
                self.ast = ast.parse(srcleft)
                self.source = src
                return
            except IndentationError:
                pass
            except SyntaxError:
                pass
        raise RuntimeError('Failed to parse:\n{}\n'.format(src))
        
    def visit_Call(self, node):
        """
        Called for all ``ast.Call`` nodes. Collects source of each argument.
        Note that AST ``starargs`` and ``keywords`` properties are not
        considered. Because ``CallArgs`` parses just one line of source code out
        of its module's context, ``ast.parse`` assumes that arguments are
        normal, not ``*args``. And ``**kwargs`` we can ignore, because those are
        pragmas, not data.
        """
        
        def call_name(n):
            """
            Given an ast.Call node, return the name of the called function, if
            discoverable. Only attempts to decode the common ``func()`` and
            ``object.method()`` cases that we care about for the ``show``
            module. Others return ``None``.
            """
            if isinstance(n.func, ast.Name):
                return n.func.id
            elif isinstance(n.func, ast.Attribute):
                a = n.func
                if isinstance(a.value, ast.Name):
                    return '.'.join([a.value.id, a.attr])
                else:
                    return None # could be an attribute of a call, but for those, we don't much care
            else:
                raise ValueError("Uh...I'm confused!")
        
        name = call_name(node)
        if name in self.TARGET_FUNCS:
            self.args = [ codegen.to_source(arg) for arg in node.args ]
        else:
            # visit its children
            ast.NodeVisitor.generic_visit(self, node)

# probably cannot make this work from interactive Python
# http://stackoverflow.com/questions/13204161/how-to-access-the-calling-source-line-from-interactive-shell

class Show(object):
    """Show objects print debug output in a 'name: value' format that
    is convenient for discovering what's going on as a program runs."""
    
    options = Options(
        show_module=False,  # Show the module name in the call location
        where=False,        # show the call location of each call
        sep="  ",           # separate items with two spaces, by default
        retvalue=False,     # return the value printed?
    )

    def __init__(self, **kwargs):
        self.options = Show.options.push(kwargs)
        self.say = Say(retvalue=self.options.retvalue)
        self.opts = None  # per call options, set on each call to reflect transient state
    
    def call_location(self, caller):
        """
        Create a call location string indicating where a show() was called.
        """
        if isInteractive:
            return "<stdin>:{0}".format(len(history.lines))
        else:
            module_name = ""
            if self.opts.show_module:
                filepath = caller.f_locals.get('__file__', caller.f_globals.get('__file__', 'UNKNOWN'))
                filename = os.path.basename(filepath)
                module_name = re.sub(r'.py', '', filename)
            
            lineno = caller.f_lineno
            co_name = caller.f_code.co_name
            if co_name == '<module>':
                co_name = '__main__'
            func_location = wrapped_if(module_name, ":") + wrapped_if(co_name, "", "()")
            return ':'.join([func_location, str(lineno)])
    
    def arg_format(self, name, value, caller):
        """Format a single argument. Strings returned as-is."""
        if name.startswith(QUOTE_CHARS):
            return fmt(value, **{'_callframe': caller})
        else:
            formatted = "{0}: {1!r}".format(name, value)
            if isinstance(value, dict):
                # escape { and }
                formatted = formatted.replace('{', '{{').replace('}', '}}') # escape for dict case
            return formatted

    def arg_format_items(self, name, value, caller):
        """Format a single argument. Strings returned as-is."""
        if name.startswith(QUOTE_CHARS):
            ret = fmt(value, **{'_callframe': caller})
            return ret
        else:                
            if isinstance(value, (list, dict, set, six.string_types)):  # weak test
                length = len(value)
                itemname = 'char' if isinstance(value, six.string_types) else 'item'
                s_or_nothing = '' if length == 1 else 's'
                return "{0} ({1} {2}{3}): {4!r}".format(name, length, itemname, s_or_nothing, value)
            else:
                return "{0}: {1!r}".format(name, value)
        
    def get_arg_tuples(self, caller, values):
        """
        Return a list of argument name, value tuples with the given values.
        """
        filename, lineno = frame_to_source_info(caller)
        argnames = CallArgs(filename, lineno).args
        argtuples = list(zip(list(argnames), list(values)))
        return argtuples
    
    def settings(self, **kwargs):
        """
        Open a context manager for a `with` statement. Temporarily change settings
        for the duration of the with.
        """
        return ShowContext(self, kwargs)
    
    def set(self, **kwargs):
        """
        Open a context manager for a `with` statement. Temporarily change settings
        for the duration of the with.
        """
        self.options.set(**kwargs)
        if kwargs:
            self.say.set(**kwargs)
    
    def clone(self, **kwargs):
        """
        Create a new Say instance whose options are chained to this instance's
        options (and thence to Say.options). kwargs become the cloned instance's
        overlay options.
        """
        cloned = Show()
        cloned.options = self.options.push(kwargs)
        return cloned

    def __call__(self, *args, **kwargs):
        """Main entry point for Show objects."""

        opts = self.opts = self.options.push(kwargs)
        
        # Determine argument names and values
        caller = inspect.currentframe().f_back
        argtuples = self.get_arg_tuples(caller, args)
        
        # Construct the result string
        valstr = opts.sep.join([ self.arg_format(name, value, caller) for name, value in argtuples ])
        locval = [ self.call_location(caller) + ":  ", valstr ] if opts.where else [ valstr ]

        # Emit the result string, and optionally return it
        retval = self.say(*locval, **kwargs)
        if opts.retvalue:
            return retval
        
    def items(self, *args, **kwargs):
        
        opts = self.opts = self.options.push(kwargs)
        
        assert len(args) == 1
        
        # Determine argument names and values
        caller = inspect.currentframe().f_back
        argtuples = self.get_arg_tuples(caller, args)
        # say("argtuples = {argtuples!r}")

        valstr = opts.sep.join([ self.arg_format_items(name, value, caller) for name, value in argtuples ])
        locval = [ self.call_location(caller) + ":  ", valstr ] if opts.where else [ valstr ]

        retval = self.say(*locval, **kwargs)
        if opts.retvalue:
            return retval

class ShowContext(OptionsContext):
    """
    Context helper to support Python's with statement.  Generally called
    from ``with show.settings(...):``
    """
    pass

show = Show()