Skip to content
Permalink
Browse files

[Processing] Manage optional parameters

Can't set parameters to null (None or '') if the parameter is not optional
  • Loading branch information
rldhont authored and volaya committed Nov 4, 2015
1 parent 55e75ad commit 3472ac80d8bdd030090ce81cb686f3cfcbd913cd
Showing with 49 additions and 27 deletions.
  1. +49 −27 python/plugins/processing/core/parameters.py
@@ -76,6 +76,11 @@ def setValue(self, obj):
Returns true if the value passed is correct for the type
of parameter.
"""
if obj is None:
if not self.optional:
return False
self.value = None
return True
self.value = unicode(obj)
return True

@@ -111,6 +116,8 @@ def __init__(self, name='', description='', default=True):

def setValue(self, value):
if value is None:
if not self.optional:
return False
self.value = self.default
return True
if isinstance(value, basestring):
@@ -133,6 +140,8 @@ def __init__(self, name='', description='', default='EPSG:4326'):

def setValue(self, value):
if value is None:
if not self.optional:
return False
self.value = self.default
return True

@@ -167,7 +176,9 @@ def __init__(self, name='', description='', default='0,1,0,1'):

def setValue(self, text):
if text is None:
self.value = self.default
if not self.optional:
return False
self.value = None

This comment has been minimized.

Copy link
@m-kuhn

m-kuhn Nov 11, 2015

Member

Should that return self.default instead of None? If not, what is the member variable self.default used for? Starting to work on a test suite and some old tests complain here and I wonder if I need to adjust the test or the code.

This comment has been minimized.

Copy link
@m-kuhn

m-kuhn Nov 20, 2015

Member

@rldhont It seems that the default parameter is no longer used for anything here. Is my assumption correct and is this intended behavior?

This comment has been minimized.

Copy link
@rldhont

rldhont Nov 20, 2015

Author Contributor

The default valude is no longer used here. If an ParameterExtent is optional it can be None else it has to be set.

This comment has been minimized.

Copy link
@m-kuhn

m-kuhn Nov 20, 2015

Member

So it should also be removed from the constructor?

This comment has been minimized.

Copy link
@rldhont

rldhont Nov 20, 2015

Author Contributor

I think so, @volaya ?

This comment has been minimized.

Copy link
@m-kuhn

m-kuhn Nov 29, 2015

Member

@volaya what are your thoughts about this?
Does "optional" remove the need for a "default" parameter?

IMO it could also be considered to allow both: Specifying a hardcoded default parameter and a special value for "let the algorithm decide what's best" (I think that's what "optional" does?).

This comment has been minimized.

Copy link
@michaelkirk

michaelkirk Nov 29, 2015

Contributor

It's strange that the ParameterCRS and the ParameterBoolean which are not optional will reset to the default value when assigning None, whereas ParameterExtent will retain it's old value. It should be consistent.

Specifically, this is the current behavior:

param = ParameterNumber('name', 'desc', 0, 10, optional=True)
assert param.setValue(3)
assert param.value == 3
assert param.setValue(None)
assert param.value == param.default

#whereas
param = ParameterExtent('name', 'desc', optional=True)
assert param.setValue('1,2,3,4')
assert param.value == '1,2,3,4'
assert param.setValue(None)
assert param.value == None
return True
tokens = text.split(',')
if len(tokens) != 4:
@@ -203,8 +214,7 @@ def setValue(self, obj):
if self.value.strip() == '' or self.value is None:
if not self.optional:
return False
else:
self.value = ''
self.value = ''
if self.ext is not None and self.value != '':
return self.value.endswith(self.ext)
return True
@@ -229,6 +239,11 @@ def __init__(self, name='', description='', numRows=3,
self.value = None

def setValue(self, obj):
if obj is None:
if not self.optional:
return False
self.value = None
return True
# TODO: check that it contains a correct number of elements
if isinstance(obj, (str, unicode)):
self.value = obj
@@ -276,11 +291,10 @@ def __init__(self, name='', description='', datatype=-1, optional=False):
def setValue(self, obj):
self.exported = None
if obj is None:
if self.optional:
self.value = None
return True
else:
if not self.optional:
return False
self.value = None
return True

if isinstance(obj, list):
if len(obj) == 0:
@@ -417,7 +431,9 @@ def __init__(self, name='', description='', minValue=None, maxValue=None,

def setValue(self, n):
if n is None:
self.value = self.default
if not self.optional:
return False
self.value = None
return True
try:
if float(n) - int(float(n)) == 0:
@@ -453,7 +469,9 @@ def __init__(self, name='', description='', default='0,1'):

def setValue(self, text):
if text is None:
self.value = self.default
if not self.optional:
return False
self.value = None
return True
tokens = text.split(',')
if len(tokens) != 2:
@@ -510,11 +528,10 @@ def getSafeExportedLayer(self):
def setValue(self, obj):
self.exported = None
if obj is None:
if self.optional:
self.value = None
return True
else:
if not self.optional:
return False
self.value = None
return True
if isinstance(obj, QgsRasterLayer):
self.value = unicode(obj.dataProvider().dataSourceUri())
return True
@@ -552,6 +569,8 @@ def __init__(self, name='', description='', options=[], default=0, isSource=Fals

def setValue(self, n):
if n is None:
if not self.optional:
return False
self.value = self.default
return True
try:
@@ -577,10 +596,9 @@ def __init__(self, name='', description='', default='', multiline=False,

def setValue(self, obj):
if obj is None:
if self.optional:
self.value = ''
return True
self.value = self.default
if not self.optional:
return false
self.value = ''
return True
self.value = unicode(obj).replace(
ParameterString.ESCAPED_NEWLINE,
@@ -604,11 +622,10 @@ def __init__(self, name='', description='', optional=False):
def setValue(self, obj):
self.exported = None
if obj is None:
if self.optional:
self.value = None
return True
else:
if not self.optional:
return False
self.value = None
return True
if isinstance(obj, QgsVectorLayer):
source = unicode(obj.source())
self.value = source
@@ -679,7 +696,10 @@ def getValueAsCommandLineParameter(self):

def setValue(self, value):
if value is None:
return self.optional
if not self.optional:
return False
self.value = None
return True
elif len(value) > 0:
self.value = unicode(value)
else:
@@ -721,11 +741,10 @@ def __init__(self, name='', description='', shapetype=[-1],
def setValue(self, obj):
self.exported = None
if obj is None:
if self.optional:
self.value = None
return True
else:
if not self.optional:
return False
self.value = None
return True
if isinstance(obj, QgsVectorLayer):
self.value = unicode(obj.source())
return True
@@ -814,7 +833,10 @@ def getValueAsCommandLineParameter(self):

def setValue(self, value):
if value is None:
return self.optional
if not self.optional:
return False
self.value = None
return True
elif len(value) == 0:
return self.optional
if isinstance(value, unicode):

29 comments on commit 3472ac8

@volaya

This comment has been minimized.

Copy link
Contributor

@volaya volaya replied Nov 30, 2015

Optional does not remove de need for a defualt value. The default is shown to the user in the UI, so the UI must be able to somehow retrieve that value. I think an optional value is just one that can accept a None valu (or not be present when calling the algorihtm, so it can be omitted), so it's more in terms of syntax

@volaya

This comment has been minimized.

Copy link
Contributor

@volaya volaya replied Nov 30, 2015

the problem i see is that the meaning of "optional" might not be the same for all types of parameters. For instance, an extent can really be "optional", meaning that, the algorithm can run without it. If you have a extent parameter called "Crop result to extent", if you do not add it, it does not crop anythin but the algorithm runs normally. For a number value, like the "buffer distance" in a buffer algorithm, optional means "use whatever default value you have", but still that value is needed. It cannot be None.

All numerical values in the current algorithms are like that. That's the reason why there were no optiona numbers before, but i added them as requested, and the same for other types of parameters. But the meaning of being optional is not exactly the same in all cases

@m-kuhn

This comment has been minimized.

Copy link
Member

@m-kuhn m-kuhn replied Nov 30, 2015

Would you agree that the concept of optional in general is to ask the algorithm to do whatever it thinks is best? This can depend on the algorithm and parameter obviously. Just what happens if an external binary is called without specifying a particular parameter.

Anyway, do you agree that the behavior should be the following?

  • If a parameter is optional and None is given: omit it.
  • If a parameter is not optional and None is given: use the default.
@volaya

This comment has been minimized.

Copy link
Contributor

@volaya volaya replied Nov 30, 2015

"If a parameter is not optional and None is given: use the default."

That not the case in parameters such us layers or tables (the only ones that were optional at first). If it's not optional (like a DEM in a Slope algorithm), None is not allowed, there must be a valid layer, otherwise it throws an exception. In this case, there is no default

Other than that, what you propose makes sense

@m-kuhn

This comment has been minimized.

Copy link
Member

@m-kuhn m-kuhn replied Nov 30, 2015

Does it make sense for other parameters to define None as default value for non-optional parameters?
Or can they all throw exceptions in this scenario?

@volaya

This comment has been minimized.

Copy link
Contributor

@volaya volaya replied Nov 30, 2015

They all should throw exceptions if None is not a valid value...and there is no default value to resort to in that case

@m-kuhn

This comment has been minimized.

Copy link
Member

@m-kuhn m-kuhn replied Nov 30, 2015

Thanks @volaya
@rldhont do you agree with this? Can you take care of that?

Glad the tests already discovered something :)

@rldhont

This comment has been minimized.

Copy link
Contributor Author

@rldhont rldhont replied Dec 2, 2015

Hi @m-kuhn and @volaya,

To be sure, I'd like to resume the comportement if value is set to None:

  • For non-optionnal parameter without default value (layer, table, etc): throw an exception
  • For non-optionnal parameter with default value (String, Number, etc): set value to default ? or throw an error ?
  • For optionnal parameter with default value: set value to default ? or to None ?
  • For optionnal parameter without default value: set value to None

I'm not sure to have well understand what you should when a parameter has a default value.

@michaelkirk

This comment has been minimized.

Copy link
Contributor

@michaelkirk michaelkirk replied Dec 2, 2015

I'm working on improving the test coverage of the parameters module, and am interested in incorporating the results of this discussion.

Just from a code standpoint, I don't get why "optional" parameter is given a default value when the user has assigned it to be None. That's not optional per se, it's just optional for the user to specify it. It will always have a value, it just might be the default specified in the constructor. If you are saying that you want it to be "optional" for the user to specify, but it must always have some Value can that be accomplished by making it required and have a default?

Examples are helpful - Do any algorithms come to mind that use these parameters in this interesting way?

@m-kuhn

This comment has been minimized.

Copy link
Member

@m-kuhn m-kuhn replied Dec 2, 2015

Aren't we mixing up parameter type and parameter here?

I'm making the following example up, just to show the point but don't blame me on them

  • A parameter type CRS can be optional or have a default
  • An algorithm reproject does have a parameter (of type CRS) target CRS. This is not optional and can have a default of 4326 (meaning: if not specified otherwise)
  • An other algorithm rasterize does have a parameter (of type CRS) target CRS. This is optional as in: if unspecified it will be taken from the source layer.

I don't see why different parameter types should handle optional and default values differently. It should be possible to specify a default for all of them (although it doesn't make much sense for a layer, but why prohibit it?) and to make them all optional.

@michaelkirk

This comment has been minimized.

Copy link
Contributor

@michaelkirk michaelkirk replied Dec 2, 2015

Disclaimer: I've never written a processing plugin 😊

Aren't we mixing up parameter type and parameter here?

I'm not sure what you mean. Are you trying to distinguish between processing.core.parameters.Parameter() and processing.core.parameters.Parameter().value ?

@m-kuhn

This comment has been minimized.

Copy link
Member

@m-kuhn m-kuhn replied Dec 2, 2015

And neither did I 😊

I am trying to distinguish between the class processing.core.parameters.Parameter (as in paramter type) and an instance of it (as in parameter).

The class should support the concept of being optional while each instance can be tagged if it is optional.

@rldhont

This comment has been minimized.

Copy link
Contributor Author

@rldhont rldhont replied Dec 3, 2015

Sorry but I'd like to know if we have to update the way Processing manage optional parameter.

I'd like to know how to manage set value :

  • For non-optionnal parameter with default value (String, Number, etc): set value to default ? or throw an error ?
  • For optionnal parameter with default value: set value to default ? or to None ?

Second question, for which parameter type do you think Processing not well manage set value to None ?

@m-kuhn

This comment has been minimized.

Copy link
Member

@m-kuhn m-kuhn replied Dec 3, 2015

Actually, I do not feel authoritative for this at all. I'd really appreciate @volaya to take the decision.

@michaelkirk

This comment has been minimized.

Copy link
Contributor

@michaelkirk michaelkirk replied Dec 6, 2015

I've made explicit some of the optional/default behavior in #2541

See the various testOptional methods.

@volaya

This comment has been minimized.

Copy link
Contributor

@volaya volaya replied Dec 14, 2015

For the record, I met @rldhont last week at the Frech QGIs meeting adn we discussed about this. He will write down the cases and how parameters should behave, according to that discussion, and put it here so you can check it, and I will implement that.

The rationale is that the design of parameters was mainly conceived for using Processing from QGIS desktop (toolbox, console, etc), but for the case of using it in the server (WPS), the situation is a bit different,, as he is finding out. Changes are not likely to affect the desktop interface or break stuff, but will allow him to have a better implementation on the server side. Hopefully, they will not look counterintuitive on the desktop side of things.

@rldhont

This comment has been minimized.

Copy link
Contributor Author

@rldhont rldhont replied Dec 14, 2015

Hi @volaya @michaelkirk and @m-kuhn

Here is the way, I think, the setValue method has to be:

    def setValue(self, obj):
        if obj is None:
            self.value = self.default
            if not self.optional and self.default is None:
                return False
            return True
        self.value = unicode(obj)
        return True

I think that if the parameter's value is set to None the value has to be the default one and this set is valid (return True) if the parameter is optional or if the parameter is not optional but with a not None default value.

This can be applied to all parameters:

Param not optional and default is None not optional and default not None optional and default not None optional and default is None
Boolean x set to default and return True set to default and return True x
Crs set to None and return False set to default and return True set to default and return True set to None and return True
Extent set to None and return False set to default and return True set to default and return True set to None and return True
File set to '' and return False set to default and return True set to default and return True set to '' and return True
FixedTable set to None and return False set to default and return True set to default and return True set to None and return True
MultipleInput set to None and return False set to default and return True set to default and return True set to None and return True
Number set to default and return False set to default and return True set to default and return True set to default and return True
Range set to None and return False set to default and return True set to default and return True set to None and return True
Raster set to None and return False set to default and return True set to default and return True set to None and return True
Extent set to None and return False set to default and return True set to default and return True set to None and return True
Selection x set to default and return True set to default and return True x
String set to '' and return False set to default and return True set to default and return True set to '' and return True
Table set to None and return False set to default and return True set to default and return True set to None and return True
TableField set to None and return False set to default and return True set to default and return True set to None and return True
Vector set to None and return False set to default and return True set to default and return True set to None and return True
GeometryPredicate set to None and return False set to default and return True set to default and return True set to None and return True

Are-you agree with all of these ?

@volaya

This comment has been minimized.

Copy link
Contributor

@volaya volaya replied Dec 15, 2015

Waiting for the comments of @m-kuhn and @michaelkirk, but that sounds good to me. Pity that we cannot use that code snippet for the parent Parameter class (since there are specific checks for each parameter type), but it should be an easy work to adapt the parameters module to this. I will work on it if no one says anything against it

Thanks for the nice summary!

@volaya

This comment has been minimized.

Copy link
Contributor

@volaya volaya replied Dec 15, 2015

Started working on this. Have a minor comment.

What happens if the default is a not-None value (let's say, for a crs parameter, the default is "EPSG:4326") but the user wants to set None as the value (for instance, to indicate that there is no need to use any CRS for reprojecting the output)?

I think that this is a corner case, and probably be handled with a subclass of the ParameterXXX class, but just wanted to mention it.

@m-kuhn

This comment has been minimized.

Copy link
Member

@m-kuhn m-kuhn replied Dec 15, 2015

Nice list @rldhont . I'd say this should go into the documentation somewhere so this work is not in vain.

Concerning the snippet: If False is returned, I would suggest the value should not be changed at all.

@volaya Can we use this in the parent class and implement a setValueCheck method only where required in subclasses which is called from the default setValue method?

Or overwrite setValue it in subclasses to do the check and then call the parent's default implementation?


@volaya I think the None value is used ambiguously: For "not set" and for "set default". There should probably be a value Parameter.default or similar that can be used to explicitly specify using the default value.

None should be reserved for "not set". For mandatory (non-optional) parameters None can be treated as Parameter.Default or even better (if it doesn't break existing code) an exception could be thrown : "You are trying to set None on a mandatory parameter: bad idea!".

@volaya

This comment has been minimized.

Copy link
Contributor

@volaya volaya replied Dec 15, 2015

good catch @m-kuhn. All parameters shoud have a parameter.default value, so instead of using None, one could do param.setValue(param.default), and leave setValue(None) to indicate that the parameter doesnt have a value and should not be used (which would return false if the parameter is mandatory).

That was more or less how it was before, i think... I would let @rldhont comment on this approach. I find it easier to understand, but not sure if it might cause some issues in the QGIS server side.

@rldhont

This comment has been minimized.

Copy link
Contributor Author

@rldhont rldhont replied Dec 15, 2015

Thanks @volaya and @m-kuhn for your review.


Firstly, what about set value to the default one during instantiation ?


@volaya for crs parameter, the default value can be None, because if the parameter is optional he can not be set.
@m-kuhn, I think that do a setValue to None is equal to reset value to default. And setValue returns if the setValue done is valid for running the algorithm.
For me the problem with not modifying value when None is passed, is that the parameter will stay at the previous value. It will never arrive in the UI, but can be do in python script.

@michaelkirk

This comment has been minimized.

Copy link
Contributor

@michaelkirk michaelkirk replied Dec 15, 2015

I think I'm repeating what @m-kuhn described, but just to reiterate maybe:

param.setValue(arg) should do one of two things -

1.) When the arg is valid*, set the param.value, return true (this may entail mutating the arg, e.g. extent parameter )
2.) When the arg is invalid, don't touch param.value, return false

*Validity is described by the ParameterType (e.g. a NumberParameter should get a number value) and optionality (setting None to a required type is invalid).

The way to reset the default should be param.setValue(param.default) or we could add a param.setDefaultValue if we want to get fancy. Equating param.setValue(None) to param.resetDefaultValue is not intuitive.

Thanks for putting this extensive table together @rldhont. I think executable test cases are a good form of documentation for something like this. I've spelled out some of the test cases in #2541, consider using it as part of your changes @volaya.

@m-kuhn

This comment has been minimized.

Copy link
Member

@m-kuhn m-kuhn replied Dec 15, 2015

+1 for bundling this with #2541

@volaya

This comment has been minimized.

Copy link
Contributor

@volaya volaya replied Dec 16, 2015

So, to make it clear, the proposal in the last comment by @michaelkirk ...would that be ok for you, @rldhont ? I find it to be intuitive and nice

If in the server side you need to set the default if None is passed, you can put that logic outside of Processing itself, in the server code, and if the value is None, call param.setDefaultValue()

Another thing we can do is to expose a method param.checkValidity(value), so you can check the validity of a value for a given parameter, without changing its current value

That might add some extra code to the server side, but it will leave the implementation in Processing much clearer and more intuitive.

@m-kuhn, @michaelkirk: opinions?

@rldhont

This comment has been minimized.

Copy link
Contributor Author

@rldhont rldhont replied Dec 16, 2015

For server side, I use Processing.runAlgorithm(alg, None, args) and I need that some input has None value. So If we add checkValidity or setDefaultValue, I'll update this method.

@volaya, @m-kuhn and @michaelkirk: how we organize us ?
First merge #2541 ? Then add CheckValidity and setDefaultValue ? At last update rumAlgorithm ?

@m-kuhn

This comment has been minimized.

Copy link
Member

@m-kuhn m-kuhn replied Dec 16, 2015

I'd say start with setDefaultValue() and runAlgorithm() in this PR, then merge #2541 into this PR and make sure the two are compatible. Not sure about checkValidity() afaics it's an optional added value which can easily be added later?

Thank you all for your work!

@michaelkirk

This comment has been minimized.

Copy link
Contributor

@michaelkirk michaelkirk replied Dec 16, 2015

@rldhont if you'd like to update the test cases as you go, I'd suggest first merging #2541. Otherwise, I'm happy to help with updating the test cases to reflect the new behavior.

@rldhont

This comment has been minimized.

Copy link
Contributor Author

@rldhont rldhont replied Dec 16, 2015

To continue the discussion, you'll find proposal code at the PR #2590 [Processing] Manage default value for parameter

Please sign in to comment.
You can’t perform that action at this time.