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style: Fix raise-without-from-inside-except (B904) #4032

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style: Fix raise-without-from-inside-except (B904) #4032

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d1f0e0e
style: Fix raise-without-from-inside-except (B904)
echoix Jul 8, 2024
7f0043d
Update frame.py
echoix Jul 13, 2024
eec6c40
Merge branch 'main' into fix-raise-without-from-inside-except
echoix Aug 1, 2024
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2 changes: 1 addition & 1 deletion gui/wxpython/iscatt/plots.py
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Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,7 @@
'The Scatterplot Tool needs the "matplotlib" '
"(python-matplotlib) package to be installed. {0}"
).format(e)
)
) from e

import grass.script as gs
from grass.pydispatch.signal import Signal
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2 changes: 1 addition & 1 deletion gui/wxpython/timeline/frame.py
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Expand Up @@ -43,7 +43,7 @@
"(python-matplotlib and on some systems also python-matplotlib-wx) "
"package(s) to be installed. {}"
).format(e)
)
) from e

import grass.script as gs

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2 changes: 1 addition & 1 deletion gui/wxpython/tplot/frame.py
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Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,7 @@
'The Temporal Plot Tool needs the "matplotlib" '
"(python-matplotlib) package to be installed. {0}"
).format(e)
)
) from e
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I tried to understand the issue. Not sure if I got it completly right. My interpretation would be, that authors did not want excepting-chaining when they included the previous exception text with format in the raised exception...
So from e would print e twice in this case, no? So probably, from None is the right choice when the original Error message is included in the raised exception? Not sure when one should raise a python error instead of a eg. gs.fatal(())_ ... Maybe @wenzeslaus has some thoughts on exception chaining?

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I don't think exception chaining was used at all before. We're way more precise about our python usage now than when the python code started, so I'm pretty sure not everything was thoroughly though out before.

But for this case, maybe forgetting the .format(e) and using exception chaining for the details is in the same spririt?
The spirit (as I understand), was to have better error messages that what python was giving at the time. Now, especially in the latests versions, have been giving better error messages, so it's less frightening and more useful. I think there's value of having the real errors showed up (as we will be having that in the logs in the issues the users will file), and we might want to have all that extra context.

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Oh, it's only a hint for an import error. So that's kinda easy and has no real implications for the logic of the code itself. It's only a nice-to-have hint.

So, I'm suggesting exception chaining without the format(e) here, it will give something similar to the example of python docs:

>>> def func():
...    raise ConnectionError
... 
>>> try:
...     func()
... except ConnectionError as exc:
...     raise RuntimeError('Failed to open database') from exc
... 
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "<stdin>", line 2, in func
ConnectionError

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
RuntimeError: Failed to open database
>>> def func():
...    raise ConnectionError
... 
>>> try:
...     func()
... except ConnectionError as exc:
...     raise RuntimeError('Failed to open database') from exc
... 
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "<stdin>", line 2, in func
ConnectionError

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
RuntimeError: Failed to open database
try:
    import matplotlib as mpl
    # The recommended way to use wx with mpl is with the WXAgg
    # backend.
    mpl.use("WXAgg")
    from matplotlib.figure import Figure
    from matplotlib.backends.backend_wxagg import (
        FigureCanvasWxAgg as FigCanvas,
        NavigationToolbar2WxAgg as NavigationToolbar,
    )
    import matplotlib.dates as mdates
except ImportError as e:
    raise ImportError(
        _(
            'The Temporal Plot Tool needs the "matplotlib" '
            "(python-matplotlib) package to be installed."
        )
    ) from e

giving (except for the line numbers and file names, I wrote it by hand):

Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "<stdin>", line 2, in func
ImportError

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
ImportError: The Temporal Plot Tool needs the "matplotlib" (python-matplotlib) package to be installed.

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Or maybe we'd want to use exception notes: https://docs.python.org/3/tutorial/errors.html#enriching-exceptions-with-notes?

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Both exception chaining and exception notes seem OK to me. However, I tend to think that all tracebacks also could be considered bugs, and when we catch an exception with try except, a simple (error-) message should be given that is addressed to the user and not to a developer who should be able to read traceback...
Maybe this discussion would make a good startingpoint to improve the exception-handling section in the style-guide?!?

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As for dependencies, see also https://trac.osgeo.org/grass/ticket/2895

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Even then, that ticket is starting to get old, now everything should be in a pyproject.toml. For addons, I think each should be an individual "real" python package, each with a pyproject.toml, and could be fetched only for that subdirectory and work perfectly (and allow code tools to understand that structure).

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Making addons python packages is also the way QGIS is going, I think. However, we also have C-addons and addons using R...

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I didn't go with the TODO finally. Still working on the next PR, the unsafe fixes are a little longer to go through, and I have to do more manual tuning.

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@neteler do you have any opions/thoughts on raised exceptions, exception chaining vs. GRASS messages (fatal/error)?
See also my comment here: #4032 (comment)



import grass.temporal as tgis
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2 changes: 1 addition & 1 deletion python/grass/pygrass/modules/interface/module.py
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Original file line number Diff line number Diff line change
Expand Up @@ -555,7 +555,7 @@ def __init__(self, cmd, *args, **kargs):
except OSError as e:
print("OSError error({0}): {1}".format(e.errno, e.strerror))
str_err = "Error running: `%s --interface-description`."
raise GrassError(str_err % self.name)
raise GrassError(str_err % self.name) from e
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Suggested change
raise GrassError(str_err % self.name) from e
raise GrassError(str_err % self.name) from None

Maybe here, and in similar cases too?

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The code around here is weird, we shouldn't be using print for this there. (It was out of scope of the PR, so I wasn't changing everything, in order to be reviewable). But None makes sense, as OSError is only to know what that we couldn't find the module (or fails), it's not the real exception.

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You can get PermissionError or FileNotFoundError which is likely a relevant info. The from e will preserve that, no? ...if yes, that would be an improvement. Semantic of GrassError is not clear to me and Error running: is more hiding than explaining what happened here. The print seems to assume some usage and tries to add convenience. ...yep, some deeper revision would be nice.

# get the xml of the module
self.xml = get_cmd_xml.communicate()[0]
# transform and parse the xml into an Element class:
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4 changes: 2 additions & 2 deletions python/grass/pygrass/raster/category.py
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Original file line number Diff line number Diff line change
Expand Up @@ -109,8 +109,8 @@ def _chk_index(self, index):
if type(index) == str:
try:
index = self.labels().index(index)
except ValueError:
raise KeyError(index)
except ValueError as error:
raise KeyError(index) from error
return index

def _chk_value(self, value):
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4 changes: 3 additions & 1 deletion python/grass/pygrass/rpc/base.py
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Expand Up @@ -173,7 +173,9 @@ def safe_receive(self, message):
except (EOFError, OSError, FatalError) as e:
# The pipe was closed by the checker thread because
# the server process was killed
raise FatalError("Exception raised: " + str(e) + " Message: " + message)
raise FatalError(
"Exception raised: " + str(e) + " Message: " + message
) from e
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Suggested change
) from e
) from None

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This one I'm not sure we'd want this, because there are multiple types of errors caught. So the traceback will be able to tell us which one is the direct cause of the others


def stop(self):
"""Stop the check thread, the libgis server and close the pipe
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6 changes: 3 additions & 3 deletions python/grass/pygrass/vector/table.py
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Expand Up @@ -859,10 +859,10 @@ def connection(self):
return psycopg2.connect(db)
except ImportError:
er = "You need to install psycopg2 to connect with this table."
raise ImportError(er)
raise ImportError(er) from None
else:
str_err = "Driver is not supported yet, pleas use: sqlite or pg"
raise TypeError(str_err)
raise TypeError(str_err) from None
Comment on lines 860 to +865
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Wouldn't the except ImportError: raise ImportError cases be best handled by add_note...raise? I would say yes, except that we need to wait for min Python on main version to be raised to 3.11 (PEP).

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It's always possible to use the feature if it is available and let it go if not supported. Or do a fallback of some sort, that adds the text to the message instead.


def table(self):
"""Return a Table object.
Expand Down Expand Up @@ -1204,7 +1204,7 @@ def execute(self, sql_code=None, cursor=None, many=False, values=None):
"The SQL statement is not correct:\n%r,\n"
"values: %r,\n"
"SQL error: %s" % (sqlc, values, str(exc))
)
) from exc

def exist(self, cursor=None):
"""Return True if the table already exist in the DB, False otherwise
Expand Down
10 changes: 5 additions & 5 deletions python/grass/script/core.py
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Original file line number Diff line number Diff line change
Expand Up @@ -867,8 +867,8 @@ def _parse_opts(lines):
break
try:
var, val = line.split(b"=", 1)
except ValueError:
raise SyntaxError("invalid output from g.parser: {}".format(line))
except ValueError as err:
raise SyntaxError("invalid output from g.parser: {}".format(line)) from err
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try:
var = decode(var)
val = decode(val)
Expand All @@ -877,7 +877,7 @@ def _parse_opts(lines):
"invalid output from g.parser ({error}): {line}".format(
error=error, line=line
)
)
) from error
if var.startswith("flag_"):
flags[var[5:]] = bool(int(val))
elif var.startswith("opt_"):
Expand Down Expand Up @@ -1888,7 +1888,7 @@ def _set_location_description(path, location, text):
fd.write(os.linesep)
fd.close()
except OSError as e:
raise ScriptError(repr(e))
raise ScriptError(repr(e)) from e


def _create_location_xy(database, location):
Expand Down Expand Up @@ -1939,7 +1939,7 @@ def _create_location_xy(database, location):

os.chdir(cur_dir)
except OSError as e:
raise ScriptError(repr(e))
raise ScriptError(repr(e)) from e
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This basically looks like a pointless try except, as the original Error is raised, so why using try-except here, if not the scripterror simplifies the error message presented to the user...

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ScriptError seems to be the error which is raised by related functions, so I think is is for consistency.

With that said, OSError seems like a fine exception to be raised from project creation functions (which would remove the need for try-except).



# interface to g.version
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4 changes: 2 additions & 2 deletions python/grass/script/task.py
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Expand Up @@ -502,7 +502,7 @@ def get_interface_description(cmd):
"Unable to fetch interface description for command '<{cmd}>'."
"\n\nDetails: <{det}>"
).format(cmd=cmd, det=e)
)
) from e
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Here is another (of several) examples, where the original Error messages is included in the error message that is raised at the end. So, I guess we also here could replace the formating with exception chaining?

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Maybe this one with a from None?

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The motivation for these Details: is to give user the original exception. This would be better done with chained exceptions in Python. However, the code was written with the expectation that the error will be read by a command line tool user without a traceback (or the original exception). Using from None preserves that idea, but I would be open to a solution which goes the path with less expectations about the potential usage.

Perhaps from e combined with the Details: has most information when doing print(...) and when just looking at the traceback.


desc = convert_xml_to_utf8(cmdout)
return desc.replace(
Expand Down Expand Up @@ -530,7 +530,7 @@ def parse_interface(name, parser=processTask, blackList=None):
_("Cannot parse interface description of<{name}> module: {error}").format(
name=name, error=error
)
)
) from error
task = parser(tree, blackList=blackList).get_task()
# if name from interface is different than the originally
# provided name, then the provided name is likely a full path needed
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6 changes: 3 additions & 3 deletions python/grass/script/vector.py
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Expand Up @@ -423,7 +423,7 @@ def vector_what(
try:
ret = read_command("v.what", env=env, **cmdParams).strip()
except CalledModuleError as e:
raise ScriptError(e.msg)
raise ScriptError(e.msg) from e

data = []
if not ret:
Expand All @@ -450,10 +450,10 @@ def vector_what(

try:
result = json.loads(ret, **kwargs)
except ValueError:
except ValueError as err:
raise ScriptError(
_("v.what output is not valid JSON format:\n {ret}").format(ret=ret)
)
) from err

if multiple:
for vmap in result["Maps"]:
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6 changes: 4 additions & 2 deletions python/grass/semantic_label/reader.py
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Expand Up @@ -40,7 +40,7 @@ def _read_config(self):
except json.decoder.JSONDecodeError as e:
raise SemanticLabelReaderError(
"Unable to parse '{}': {}".format(json_file, e)
)
) from e

# check if configuration is valid
self._check_config(config)
Expand Down Expand Up @@ -116,7 +116,9 @@ def print_info(self, shortcut=None, band=None, semantic_label=None, extended=Fal
if shortcut and re.match(shortcut, item["shortcut"]) is None:
continue
except re.error as e:
raise SemanticLabelReaderError("Invalid pattern: {}".format(e))
raise SemanticLabelReaderError(
"Invalid pattern: {}".format(e)
) from e

found = True
if band and band not in item["bands"]:
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14 changes: 7 additions & 7 deletions python/grass/utils/download.py
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Expand Up @@ -107,7 +107,7 @@ def extract_zip(name, directory, tmpdir):
extract_dir=extract_dir, target_dir=directory, files=files
)
except zipfile.BadZipfile as error:
raise DownloadError(_("ZIP file is unreadable: {0}").format(error))
raise DownloadError(_("ZIP file is unreadable: {0}").format(error)) from error


# modified copy from g.extension
Expand Down Expand Up @@ -167,9 +167,9 @@ def download_and_extract(source, reporthook=None):
url=source,
code=err,
),
)
except URLError:
raise DownloadError(url_error_message.format(url=source))
) from err
except URLError as e:
raise DownloadError(url_error_message.format(url=source)) from e
if headers.get("content-type", "") != "application/zip":
raise DownloadError(
_(
Expand All @@ -188,9 +188,9 @@ def download_and_extract(source, reporthook=None):
url=source,
code=err,
),
)
except URLError:
raise DownloadError(url_error_message.format(url=source))
) from err
except URLError as e:
raise DownloadError(url_error_message.format(url=source)) from e
extract_tar(name=archive_name, directory=directory, tmpdir=tmpdir)
else:
# probably programmer error
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10 changes: 5 additions & 5 deletions scripts/r.in.wms/wms_cap_parsers.py
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Expand Up @@ -41,17 +41,17 @@ def __init__(self, cap_file):
if is_file:
try:
etree.ElementTree.__init__(self, file=cap_file)
except ParseError:
raise ParseError(_("Unable to parse XML file"))
except ParseError as pe:
raise ParseError(_("Unable to parse XML file")) from pe
except OSError as error:
raise ParseError(
_("Unable to open XML file '%s'.\n%s\n" % (cap_file, error))
)
) from error
else:
try:
etree.ElementTree.__init__(self, element=etree.fromstring(cap_file))
except ParseError:
raise ParseError(_("Unable to parse XML file"))
except ParseError as pe:
raise ParseError(_("Unable to parse XML file")) from pe

if self.getroot() is None:
raise ParseError(_("Root node was not found."))
Expand Down
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