58 lines
2.4 KiB
Python
58 lines
2.4 KiB
Python
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# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
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# For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
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"""Imposter encodings module that installs a coverage-style tracer.
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This is NOT the encodings module; it is an imposter that sets up tracing
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instrumentation and then replaces itself with the real encodings module.
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If the directory that holds this file is placed first in the PYTHONPATH when
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using "coverage" to run Python's tests, then this file will become the very
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first module imported by the internals of Python 3. It installs a
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coverage.py-compatible trace function that can watch Standard Library modules
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execute from the very earliest stages of Python's own boot process. This fixes
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a problem with coverage.py - that it starts too late to trace the coverage of
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many of the most fundamental modules in the Standard Library.
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DO NOT import other modules into here, it will interfere with the goal of this
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code executing before all imports. This is why this file isn't type-checked.
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"""
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import sys
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class FullCoverageTracer:
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def __init__(self):
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# `traces` is a list of trace events. Frames are tricky: the same
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# frame object is used for a whole scope, with new line numbers
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# written into it. So in one scope, all the frame objects are the
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# same object, and will eventually all will point to the last line
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# executed. So we keep the line numbers alongside the frames.
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# The list looks like:
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#
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# traces = [
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# ((frame, event, arg), lineno), ...
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# ]
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#
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self.traces = []
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def fullcoverage_trace(self, *args):
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frame, event, arg = args
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if frame.f_lineno is not None:
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# https://bugs.python.org/issue46911
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self.traces.append((args, frame.f_lineno))
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return self.fullcoverage_trace
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sys.settrace(FullCoverageTracer().fullcoverage_trace)
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# Remove our own directory from sys.path; remove ourselves from
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# sys.modules; and re-import "encodings", which will be the real package
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# this time. Note that the delete from sys.modules dictionary has to
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# happen last, since all of the symbols in this module will become None
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# at that exact moment, including "sys".
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parentdir = max(filter(__file__.startswith, sys.path), key=len)
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sys.path.remove(parentdir)
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del sys.modules['encodings']
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import encodings
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