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@@ -313,7 +313,7 b' class FileContentsManager(ContentsManager):' | |||||
313 | bcontent = base64.decodestring(b64_bytes) |
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313 | bcontent = base64.decodestring(b64_bytes) | |
314 | except Exception as e: |
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314 | except Exception as e: | |
315 | raise web.HTTPError(400, u'Encoding error saving %s: %s' % (os_path, e)) |
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315 | raise web.HTTPError(400, u'Encoding error saving %s: %s' % (os_path, e)) | |
316 |
with atomic_writing(os_path, |
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316 | with atomic_writing(os_path, text=False) as f: | |
317 | f.write(bcontent) |
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317 | f.write(bcontent) | |
318 |
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318 | |||
319 | def _save_directory(self, os_path, model, name='', path=''): |
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319 | def _save_directory(self, os_path, model, name='', path=''): |
@@ -17,6 +17,7 b' from __future__ import absolute_import' | |||||
17 | #----------------------------------------------------------------------------- |
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17 | #----------------------------------------------------------------------------- | |
18 | import codecs |
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18 | import codecs | |
19 | from contextlib import contextmanager |
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19 | from contextlib import contextmanager | |
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20 | import io | |||
20 | import os |
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21 | import os | |
21 | import sys |
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22 | import sys | |
22 | import tempfile |
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23 | import tempfile | |
@@ -219,21 +220,55 b" def temp_pyfile(src, ext='.py'):" | |||||
219 | return fname, f |
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220 | return fname, f | |
220 |
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221 | |||
221 | @contextmanager |
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222 | @contextmanager | |
222 |
def atomic_writing(path, |
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223 | def atomic_writing(path, text=True, encoding='utf-8', **kwargs): | |
223 | tmp_file = path + '.tmp-write' |
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224 | """Context manager to write to a file only if the entire write is successful. | |
224 | if 'b' in mode: |
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225 | ||
225 | encoding = None |
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226 | This works by creating a temporary file in the same directory, and renaming | |
226 |
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227 | it over the old file if the context is exited without an error. If the | ||
227 | with open(tmp_file, mode, encoding=encoding, **kwargs) as f: |
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228 | target file is a symlink or a hardlink, this will not be preserved: it will | |
228 | yield f |
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229 | be replaced by a new regular file. | |
229 |
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230 | |||
230 | # Written successfully, now rename it |
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231 | On Windows, there is a small chink in the atomicity: the target file is | |
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232 | deleted before renaming the temporary file over it. This appears to be | |||
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233 | unavoidable. | |||
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234 | ||||
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235 | Parameters | |||
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236 | ---------- | |||
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237 | path : str | |||
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238 | The target file to write to. | |||
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239 | ||||
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240 | text : bool, optional | |||
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241 | Whether to open the file in text mode (i.e. to write unicode). Default is | |||
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242 | True. | |||
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243 | ||||
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244 | encoding : str, optional | |||
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245 | The encoding to use for files opened in text mode. Default is UTF-8. | |||
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246 | ||||
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247 | **kwargs | |||
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248 | Passed to :func:`io.open`. | |||
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249 | """ | |||
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250 | dirname, basename = os.path.split(path) | |||
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251 | handle, tmp_path = tempfile.mkstemp(prefix=basename, dir=dirname, text=text) | |||
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252 | if text: | |||
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253 | fileobj = io.open(handle, 'w', encoding=encoding, **kwargs) | |||
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254 | else: | |||
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255 | fileobj = io.open(handle, 'wb', **kwargs) | |||
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256 | ||||
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257 | try: | |||
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258 | yield fileobj | |||
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259 | except: | |||
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260 | fileobj.close() | |||
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261 | os.remove(tmp_path) | |||
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262 | raise | |||
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263 | else: | |||
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264 | # Written successfully, now rename it | |||
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265 | fileobj.close() | |||
231 |
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266 | |||
232 | if os.name == 'nt' and os.path.exists(path): |
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267 | if os.name == 'nt' and os.path.exists(path): | |
233 | # Rename over existing file doesn't work on Windows |
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268 | # Rename over existing file doesn't work on Windows | |
234 | os.remove(path) |
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269 | os.remove(path) | |
235 |
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270 | |||
236 |
os.rename(tmp_ |
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271 | os.rename(tmp_path, path) | |
237 |
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272 | |||
238 |
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273 | |||
239 | def raw_print(*args, **kw): |
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274 | def raw_print(*args, **kw): |
@@ -15,6 +15,7 b' from __future__ import print_function' | |||||
15 | from __future__ import absolute_import |
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15 | from __future__ import absolute_import | |
16 |
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16 | |||
17 | import io as stdlib_io |
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17 | import io as stdlib_io | |
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18 | import os.path | |||
18 | import sys |
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19 | import sys | |
19 |
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20 | |||
20 | from subprocess import Popen, PIPE |
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21 | from subprocess import Popen, PIPE | |
@@ -23,8 +24,11 b' import unittest' | |||||
23 | import nose.tools as nt |
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24 | import nose.tools as nt | |
24 |
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25 | |||
25 | from IPython.testing.decorators import skipif |
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26 | from IPython.testing.decorators import skipif | |
26 | from IPython.utils.io import Tee, capture_output, unicode_std_stream |
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27 | from IPython.utils.io import (Tee, capture_output, unicode_std_stream, | |
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28 | atomic_writing, | |||
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29 | ) | |||
27 | from IPython.utils.py3compat import doctest_refactor_print, PY3 |
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30 | from IPython.utils.py3compat import doctest_refactor_print, PY3 | |
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31 | from IPython.utils.tempdir import TemporaryDirectory | |||
28 |
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32 | |||
29 | if PY3: |
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33 | if PY3: | |
30 | from io import StringIO |
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34 | from io import StringIO | |
@@ -121,4 +125,27 b' def test_UnicodeStdStream_nowrap():' | |||||
121 | nt.assert_is(unicode_std_stream(), sys.stdout) |
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125 | nt.assert_is(unicode_std_stream(), sys.stdout) | |
122 | assert not sys.stdout.closed |
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126 | assert not sys.stdout.closed | |
123 | finally: |
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127 | finally: | |
124 | sys.stdout = orig_stdout No newline at end of file |
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128 | sys.stdout = orig_stdout | |
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129 | ||||
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130 | def test_atomic_writing(): | |||
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131 | class CustomExc(Exception): pass | |||
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132 | ||||
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133 | with TemporaryDirectory() as td: | |||
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134 | f1 = os.path.join(td, 'penguin') | |||
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135 | with stdlib_io.open(f1, 'w') as f: | |||
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136 | f.write(u'Before') | |||
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137 | ||||
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138 | with nt.assert_raises(CustomExc): | |||
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139 | with atomic_writing(f1) as f: | |||
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140 | f.write(u'Failing write') | |||
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141 | raise CustomExc | |||
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142 | ||||
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143 | # Because of the exception, the file should not have been modified | |||
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144 | with stdlib_io.open(f1, 'r') as f: | |||
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145 | nt.assert_equal(f.read(), u'Before') | |||
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146 | ||||
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147 | with atomic_writing(f1) as f: | |||
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148 | f.write(u'Overwritten') | |||
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149 | ||||
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150 | with stdlib_io.open(f1, 'r') as f: | |||
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151 | nt.assert_equal(f.read(), u'Overwritten') |
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