Repository: prometheus/client_python
Pull request #91 (2016-07-20 13:17:29)

Bundle decorator.py and fix decorators
As discussed in #77, this PR bundles (to avoid dependencies) the decorator.py module and uses it to fix the behavior of prometheus_client's decorators.

The efficacy can be verified by using example view from the README and then doing a:

```pycon
>>> from inspect import getargspec
>>> getargspec(process_request)
ArgSpec(args=['t'], varargs=None, keywords=None, defaults=None)
```

Without this patch, you get:

```pycon
ArgSpec(args=[], varargs='args', keywords='kwargs', defaults=None)
```

instead.

Let me now what you think.

Also pinging @micheles out of courtesy and to ensure he doesn’t feel we violate his copyright.

brian-brazil: That looks good, could you add a quick unittest so we don't accidentally regress?
micheles: Yes, no problems on my part, the decorator module is a single file just to
help people that wants to include it and have less dependencies.

On Wed, Jul 20, 2016 at 3:17 PM, Hynek Schlawack <notifications@github.com>
wrote:

> As discussed in #77
> <https://github.com/prometheus/client_python/issues/77>, this PR bundles
> (to avoid dependencies) the decorator.py module and uses it to fix the
> behavior of prometheus_client's decorators.
>
> The efficacy can be verified by using example view from the README and
> then doing a:
>
> >>> from inspect import getargspec
> >>> getargspec(process_request)
> ArgSpec(args=['t'], varargs=None, keywords=None, defaults=None)
>
> Without this patch, you get:
>
> ArgSpec(args=[], varargs='args', keywords='kwargs', defaults=None)
>
> instead.
>
> Let me now what you think.
>
> Also pinging @micheles <https://github.com/micheles> out of courtesy and
> to ensure he doesn’t feel we violate his copyright.
> ------------------------------
> You can view, comment on, or merge this pull request online at:
>
>   https://github.com/prometheus/client_python/pull/91
> Commit Summary
>
>    - Bundle decorator.py and fix decorators
>
> File Changes
>
>    - *M* .coveragerc
>    <https://github.com/prometheus/client_python/pull/91/files#diff-0> (4)
>    - *M* NOTICE
>    <https://github.com/prometheus/client_python/pull/91/files#diff-1> (3)
>    - *M* prometheus_client/core.py
>    <https://github.com/prometheus/client_python/pull/91/files#diff-2>
>    (38)
>    - *A* prometheus_client/decorator.py
>    <https://github.com/prometheus/client_python/pull/91/files#diff-3>
>    (417)
>
> Patch Links:
>
>    - https://github.com/prometheus/client_python/pull/91.patch
>    - https://github.com/prometheus/client_python/pull/91.diff
>
> —
> You are receiving this because you were mentioned.
> Reply to this email directly, view it on GitHub
> <https://github.com/prometheus/client_python/pull/91>, or mute the thread
> <https://github.com/notifications/unsubscribe-auth/ACWYcHT25T7oA9sc3uu03o9FP98mtKYiks5qXh_rgaJpZM4JQw7E>
> .
>


Patch:
diff --git a/.coveragerc b/.coveragerc
index 5ce4e22..69a0f52 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -1,6 +1,8 @@
 [run]
 branch = True
 source = prometheus_client
+omit =
+    prometheus_client/decorator.py
 
 [paths]
 source =
@@ -9,4 +11,4 @@ source =
    .tox/pypy/site-packages/prometheus_client
 
 [report]
-show_missing = True
+show_missing = True
\ No newline at end of file
diff --git a/NOTICE b/NOTICE
index 0675ae1..59efb6c 100644
--- a/NOTICE
+++ b/NOTICE
@@ -1,2 +1,5 @@
 Prometheus instrumentation library for Python applications
 Copyright 2015 The Prometheus Authors
+
+This product bundles decorator 4.0.10 which is available under a "2-clause BSD"
+license. For details, see prometheus_client/decorator.py.
diff --git a/prometheus_client/core.py b/prometheus_client/core.py
index 6619802..6e2d91d 100644
--- a/prometheus_client/core.py
+++ b/prometheus_client/core.py
@@ -14,9 +14,10 @@ except ImportError:
     # Python 3
     unicode = str
 
-from functools import wraps
 from threading import Lock
 
+from .decorator import decorate
+
 _METRIC_NAME_RE = re.compile(r'^[a-zA-Z_:][a-zA-Z0-9_:]*$')
 _METRIC_LABEL_NAME_RE = re.compile(r'^[a-zA-Z_:][a-zA-Z0-9_:]*$')
 _RESERVED_METRIC_LABEL_NAME_RE = re.compile(r'^__.*$')
@@ -657,11 +658,10 @@ class _HistogramTimer(object):
         self._histogram.observe(max(time.time() - self._start, 0))
 
     def __call__(self, f):
-        @wraps(f)
-        def wrapped(*args, **kwargs):
+        def wrapped(func, *args, **kwargs):
             with self:
-                return f(*args, **kwargs)
-        return wrapped
+                return func(*args, **kwargs)
+        return decorate(f, wrapped)
 
 
 class _ExceptionCounter(object):
@@ -677,11 +677,10 @@ class _ExceptionCounter(object):
             self._counter.inc()
 
     def __call__(self, f):
-        @wraps(f)
-        def wrapped(*args, **kwargs):
+        def wrapped(func, *args, **kwargs):
             with self:
-                return f(*args, **kwargs)
-        return wrapped
+                return func(*args, **kwargs)
+        return decorate(f, wrapped)
 
 
 class _InprogressTracker(object):
@@ -695,11 +694,10 @@ class _InprogressTracker(object):
         self._gauge.dec()
 
     def __call__(self, f):
-        @wraps(f)
-        def wrapped(*args, **kwargs):
+        def wrapped(func, *args, **kwargs):
             with self:
-                return f(*args, **kwargs)
-        return wrapped
+                return func(*args, **kwargs)
+        return decorate(f, wrapped)
 
 
 class _SummaryTimer(object):
@@ -714,11 +712,10 @@ class _SummaryTimer(object):
         self._summary.observe(max(time.time() - self._start, 0))
 
     def __call__(self, f):
-        @wraps(f)
-        def wrapped(*args, **kwargs):
+        def wrapped(func, *args, **kwargs):
             with self:
-                return f(*args, **kwargs)
-        return wrapped
+                return func(*args, **kwargs)
+        return decorate(f, wrapped)
 
 
 class _GaugeTimer(object):
@@ -733,8 +730,7 @@ class _GaugeTimer(object):
         self._gauge.set(max(time.time() - self._start, 0))
 
     def __call__(self, f):
-        @wraps(f)
-        def wrapped(*args, **kwargs):
+        def wrapped(func, *args, **kwargs):
             with self:
-                return f(*args, **kwargs)
-        return wrapped
+                return func(*args, **kwargs)
+        return decorate(f, wrapped)
diff --git a/prometheus_client/decorator.py b/prometheus_client/decorator.py
new file mode 100644
index 0000000..50876c6
--- /dev/null
+++ b/prometheus_client/decorator.py
@@ -0,0 +1,417 @@
+# #########################     LICENSE     ############################ #
+
+# Copyright (c) 2005-2016, Michele Simionato
+# All rights reserved.
+
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+
+#   Redistributions of source code must retain the above copyright
+#   notice, this list of conditions and the following disclaimer.
+#   Redistributions in bytecode form must reproduce the above copyright
+#   notice, this list of conditions and the following disclaimer in
+#   the documentation and/or other materials provided with the
+#   distribution.
+
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+# TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+# USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+# DAMAGE.
+
+"""
+Decorator module, see http://pypi.python.org/pypi/decorator
+for the documentation.
+"""
+from __future__ import print_function
+
+import re
+import sys
+import inspect
+import operator
+import itertools
+import collections
+
+__version__ = '4.0.10'
+
+if sys.version >= '3':
+    from inspect import getfullargspec
+
+    def get_init(cls):
+        return cls.__init__
+else:
+    class getfullargspec(object):
+        "A quick and dirty replacement for getfullargspec for Python 2.X"
+        def __init__(self, f):
+            self.args, self.varargs, self.varkw, self.defaults = \
+                inspect.getargspec(f)
+            self.kwonlyargs = []
+            self.kwonlydefaults = None
+
+        def __iter__(self):
+            yield self.args
+            yield self.varargs
+            yield self.varkw
+            yield self.defaults
+
+        getargspec = inspect.getargspec
+
+    def get_init(cls):
+        return cls.__init__.__func__
+
+# getargspec has been deprecated in Python 3.5
+ArgSpec = collections.namedtuple(
+    'ArgSpec', 'args varargs varkw defaults')
+
+
+def getargspec(f):
+    """A replacement for inspect.getargspec"""
+    spec = getfullargspec(f)
+    return ArgSpec(spec.args, spec.varargs, spec.varkw, spec.defaults)
+
+DEF = re.compile('\s*def\s*([_\w][_\w\d]*)\s*\(')
+
+
+# basic functionality
+class FunctionMaker(object):
+    """
+    An object with the ability to create functions with a given signature.
+    It has attributes name, doc, module, signature, defaults, dict and
+    methods update and make.
+    """
+
+    # Atomic get-and-increment provided by the GIL
+    _compile_count = itertools.count()
+
+    def __init__(self, func=None, name=None, signature=None,
+                 defaults=None, doc=None, module=None, funcdict=None):
+        self.shortsignature = signature
+        if func:
+            # func can be a class or a callable, but not an instance method
+            self.name = func.__name__
+            if self.name == '<lambda>':  # small hack for lambda functions
+                self.name = '_lambda_'
+            self.doc = func.__doc__
+            self.module = func.__module__
+            if inspect.isfunction(func):
+                argspec = getfullargspec(func)
+                self.annotations = getattr(func, '__annotations__', {})
+                for a in ('args', 'varargs', 'varkw', 'defaults', 'kwonlyargs',
+                          'kwonlydefaults'):
+                    setattr(self, a, getattr(argspec, a))
+                for i, arg in enumerate(self.args):
+                    setattr(self, 'arg%d' % i, arg)
+                if sys.version < '3':  # easy way
+                    self.shortsignature = self.signature = (
+                        inspect.formatargspec(
+                            formatvalue=lambda val: "", *argspec)[1:-1])
+                else:  # Python 3 way
+                    allargs = list(self.args)
+                    allshortargs = list(self.args)
+                    if self.varargs:
+                        allargs.append('*' + self.varargs)
+                        allshortargs.append('*' + self.varargs)
+                    elif self.kwonlyargs:
+                        allargs.append('*')  # single star syntax
+                    for a in self.kwonlyargs:
+                        allargs.append('%s=None' % a)
+                        allshortargs.append('%s=%s' % (a, a))
+                    if self.varkw:
+                        allargs.append('**' + self.varkw)
+                        allshortargs.append('**' + self.varkw)
+                    self.signature = ', '.join(allargs)
+                    self.shortsignature = ', '.join(allshortargs)
+                self.dict = func.__dict__.copy()
+        # func=None happens when decorating a caller
+        if name:
+            self.name = name
+        if signature is not None:
+            self.signature = signature
+        if defaults:
+            self.defaults = defaults
+        if doc:
+            self.doc = doc
+        if module:
+            self.module = module
+        if funcdict:
+            self.dict = funcdict
+        # check existence required attributes
+        assert hasattr(self, 'name')
+        if not hasattr(self, 'signature'):
+            raise TypeError('You are decorating a non function: %s' % func)
+
+    def update(self, func, **kw):
+        "Update the signature of func with the data in self"
+        func.__name__ = self.name
+        func.__doc__ = getattr(self, 'doc', None)
+        func.__dict__ = getattr(self, 'dict', {})
+        func.__defaults__ = getattr(self, 'defaults', ())
+        func.__kwdefaults__ = getattr(self, 'kwonlydefaults', None)
+        func.__annotations__ = getattr(self, 'annotations', None)
+        try:
+            frame = sys._getframe(3)
+        except AttributeError:  # for IronPython and similar implementations
+            callermodule = '?'
+        else:
+            callermodule = frame.f_globals.get('__name__', '?')
+        func.__module__ = getattr(self, 'module', callermodule)
+        func.__dict__.update(kw)
+
+    def make(self, src_templ, evaldict=None, addsource=False, **attrs):
+        "Make a new function from a given template and update the signature"
+        src = src_templ % vars(self)  # expand name and signature
+        evaldict = evaldict or {}
+        mo = DEF.match(src)
+        if mo is None:
+            raise SyntaxError('not a valid function template\n%s' % src)
+        name = mo.group(1)  # extract the function name
+        names = set([name] + [arg.strip(' *') for arg in
+                              self.shortsignature.split(',')])
+        for n in names:
+            if n in ('_func_', '_call_'):
+                raise NameError('%s is overridden in\n%s' % (n, src))
+
+        if not src.endswith('\n'):  # add a newline for old Pythons
+            src += '\n'
+
+        # Ensure each generated function has a unique filename for profilers
+        # (such as cProfile) that depend on the tuple of (<filename>,
+        # <definition line>, <function name>) being unique.
+        filename = '<decorator-gen-%d>' % (next(self._compile_count),)
+        try:
+            code = compile(src, filename, 'single')
+            exec(code, evaldict)
+        except:
+            print('Error in generated code:', file=sys.stderr)
+            print(src, file=sys.stderr)
+            raise
+        func = evaldict[name]
+        if addsource:
+            attrs['__source__'] = src
+        self.update(func, **attrs)
+        return func
+
+    @classmethod
+    def create(cls, obj, body, evaldict, defaults=None,
+               doc=None, module=None, addsource=True, **attrs):
+        """
+        Create a function from the strings name, signature and body.
+        evaldict is the evaluation dictionary. If addsource is true an
+        attribute __source__ is added to the result. The attributes attrs
+        are added, if any.
+        """
+        if isinstance(obj, str):  # "name(signature)"
+            name, rest = obj.strip().split('(', 1)
+            signature = rest[:-1]  # strip a right parens
+            func = None
+        else:  # a function
+            name = None
+            signature = None
+            func = obj
+        self = cls(func, name, signature, defaults, doc, module)
+        ibody = '\n'.join('    ' + line for line in body.splitlines())
+        return self.make('def %(name)s(%(signature)s):\n' + ibody,
+                         evaldict, addsource, **attrs)
+
+
+def decorate(func, caller):
+    """
+    decorate(func, caller) decorates a function using a caller.
+    """
+    evaldict = dict(_call_=caller, _func_=func)
+    fun = FunctionMaker.create(
+        func, "return _call_(_func_, %(shortsignature)s)",
+        evaldict, __wrapped__=func)
+    if hasattr(func, '__qualname__'):
+        fun.__qualname__ = func.__qualname__
+    return fun
+
+
+def decorator(caller, _func=None):
+    """decorator(caller) converts a caller function into a decorator"""
+    if _func is not None:  # return a decorated function
+        # this is obsolete behavior; you should use decorate instead
+        return decorate(_func, caller)
+    # else return a decorator function
+    if inspect.isclass(caller):
+        name = caller.__name__.lower()
+        doc = 'decorator(%s) converts functions/generators into ' \
+            'factories of %s objects' % (caller.__name__, caller.__name__)
+    elif inspect.isfunction(caller):
+        if caller.__name__ == '<lambda>':
+            name = '_lambda_'
+        else:
+            name = caller.__name__
+        doc = caller.__doc__
+    else:  # assume caller is an object with a __call__ method
+        name = caller.__class__.__name__.lower()
+        doc = caller.__call__.__doc__
+    evaldict = dict(_call_=caller, _decorate_=decorate)
+    return FunctionMaker.create(
+        '%s(func)' % name, 'return _decorate_(func, _call_)',
+        evaldict, doc=doc, module=caller.__module__,
+        __wrapped__=caller)
+
+
+# ####################### contextmanager ####################### #
+
+try:  # Python >= 3.2
+    from contextlib import _GeneratorContextManager
+except ImportError:  # Python >= 2.5
+    from contextlib import GeneratorContextManager as _GeneratorContextManager
+
+
+class ContextManager(_GeneratorContextManager):
+    def __call__(self, func):
+        """Context manager decorator"""
+        return FunctionMaker.create(
+            func, "with _self_: return _func_(%(shortsignature)s)",
+            dict(_self_=self, _func_=func), __wrapped__=func)
+
+init = getfullargspec(_GeneratorContextManager.__init__)
+n_args = len(init.args)
+if n_args == 2 and not init.varargs:  # (self, genobj) Python 2.7
+    def __init__(self, g, *a, **k):
+        return _GeneratorContextManager.__init__(self, g(*a, **k))
+    ContextManager.__init__ = __init__
+elif n_args == 2 and init.varargs:  # (self, gen, *a, **k) Python 3.4
+    pass
+elif n_args == 4:  # (self, gen, args, kwds) Python 3.5
+    def __init__(self, g, *a, **k):
+        return _GeneratorContextManager.__init__(self, g, a, k)
+    ContextManager.__init__ = __init__
+
+contextmanager = decorator(ContextManager)
+
+
+# ############################ dispatch_on ############################ #
+
+def append(a, vancestors):
+    """
+    Append ``a`` to the list of the virtual ancestors, unless it is already
+    included.
+    """
+    add = True
+    for j, va in enumerate(vancestors):
+        if issubclass(va, a):
+            add = False
+            break
+        if issubclass(a, va):
+            vancestors[j] = a
+            add = False
+    if add:
+        vancestors.append(a)
+
+
+# inspired from simplegeneric by P.J. Eby and functools.singledispatch
+def dispatch_on(*dispatch_args):
+    """
+    Factory of decorators turning a function into a generic function
+    dispatching on the given arguments.
+    """
+    assert dispatch_args, 'No dispatch args passed'
+    dispatch_str = '(%s,)' % ', '.join(dispatch_args)
+
+    def check(arguments, wrong=operator.ne, msg=''):
+        """Make sure one passes the expected number of arguments"""
+        if wrong(len(arguments), len(dispatch_args)):
+            raise TypeError('Expected %d arguments, got %d%s' %
+                            (len(dispatch_args), len(arguments), msg))
+
+    def gen_func_dec(func):
+        """Decorator turning a function into a generic function"""
+
+        # first check the dispatch arguments
+        argset = set(getfullargspec(func).args)
+        if not set(dispatch_args) <= argset:
+            raise NameError('Unknown dispatch arguments %s' % dispatch_str)
+
+        typemap = {}
+
+        def vancestors(*types):
+            """
+            Get a list of sets of virtual ancestors for the given types
+            """
+            check(types)
+            ras = [[] for _ in range(len(dispatch_args))]
+            for types_ in typemap:
+                for t, type_, ra in zip(types, types_, ras):
+                    if issubclass(t, type_) and type_ not in t.__mro__:
+                        append(type_, ra)
+            return [set(ra) for ra in ras]
+
+        def ancestors(*types):
+            """
+            Get a list of virtual MROs, one for each type
+            """
+            check(types)
+            lists = []
+            for t, vas in zip(types, vancestors(*types)):
+                n_vas = len(vas)
+                if n_vas > 1:
+                    raise RuntimeError(
+                        'Ambiguous dispatch for %s: %s' % (t, vas))
+                elif n_vas == 1:
+                    va, = vas
+                    mro = type('t', (t, va), {}).__mro__[1:]
+                else:
+                    mro = t.__mro__
+                lists.append(mro[:-1])  # discard t and object
+            return lists
+
+        def register(*types):
+            """
+            Decorator to register an implementation for the given types
+            """
+            check(types)
+
+            def dec(f):
+                check(getfullargspec(f).args, operator.lt, ' in ' + f.__name__)
+                typemap[types] = f
+                return f
+            return dec
+
+        def dispatch_info(*types):
+            """
+            An utility to introspect the dispatch algorithm
+            """
+            check(types)
+            lst = []
+            for anc in itertools.product(*ancestors(*types)):
+                lst.append(tuple(a.__name__ for a in anc))
+            return lst
+
+        def _dispatch(dispatch_args, *args, **kw):
+            types = tuple(type(arg) for arg in dispatch_args)
+            try:  # fast path
+                f = typemap[types]
+            except KeyError:
+                pass
+            else:
+                return f(*args, **kw)
+            combinations = itertools.product(*ancestors(*types))
+            next(combinations)  # the first one has been already tried
+            for types_ in combinations:
+                f = typemap.get(types_)
+                if f is not None:
+                    return f(*args, **kw)
+
+            # else call the default implementation
+            return func(*args, **kw)
+
+        return FunctionMaker.create(
+            func, 'return _f_(%s, %%(shortsignature)s)' % dispatch_str,
+            dict(_f_=_dispatch), register=register, default=func,
+            typemap=typemap, vancestors=vancestors, ancestors=ancestors,
+            dispatch_info=dispatch_info, __wrapped__=func)
+
+    gen_func_dec.__name__ = 'dispatch_on' + dispatch_str
+    return gen_func_dec


Test patch:
diff --git a/tests/test_core.py b/tests/test_core.py
index 83b15e8..52fda09 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1,4 +1,6 @@
 from __future__ import unicode_literals
+
+import inspect
 import os
 import threading
 import time
@@ -29,6 +31,8 @@ class TestCounter(unittest.TestCase):
             else:
                 raise TypeError
 
+        self.assertEqual((["r"], None, None, None), inspect.getargspec(f))
+
         try:
             f(False)
         except TypeError:
@@ -77,6 +81,8 @@ class TestGauge(unittest.TestCase):
         def f():
             self.assertEqual(1, self.registry.get_sample_value('g'))
 
+        self.assertEqual(([], None, None, None), inspect.getargspec(f))
+
         f()
         self.assertEqual(0, self.registry.get_sample_value('g'))
 
@@ -102,6 +108,8 @@ class TestGauge(unittest.TestCase):
         def f():
             time.sleep(.001)
 
+        self.assertEqual(([], None, None, None), inspect.getargspec(f))
+
         f()
         self.assertNotEqual(0, self.registry.get_sample_value('g'))
 
@@ -131,6 +139,8 @@ class TestSummary(unittest.TestCase):
         def f():
             pass
 
+        self.assertEqual(([], None, None, None), inspect.getargspec(f))
+
         f()
         self.assertEqual(1, self.registry.get_sample_value('s_count'))
 
@@ -207,6 +217,8 @@ class TestHistogram(unittest.TestCase):
         def f():
             pass
 
+        self.assertEqual(([], None, None, None), inspect.getargspec(f))
+
         f()
         self.assertEqual(1, self.registry.get_sample_value('h_count'))
         self.assertEqual(1, self.registry.get_sample_value('h_bucket', {'le': '+Inf'}))