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Posted to dev@maven.apache.org by Jochen Kuhnle <jo...@kuhnle.net> on 2007/07/03 18:05:06 UTC
Proposal: Required declaration of properties in pom.xml
Hi,
currently, Maven does not require declaration of properties used in the
pom, you just use them anywhere you like. Usually, if a property is
missing, bad things tend to happen because it is replaced with the
string "null". On a good day, resources from "translations-null-null"
aren't included in the build, on bad days it's worse... And when you
find the missing property in a pom you haven't written, you have to
figure out what "${lopt}" means and what its legal values are...
So instead typing
<properties>
<lopt>en_US</lopt>
</properties>
this proposal wants you to write
<properties>
<property>
<name>lopt</name>
<defaultValue>en_US</defaultValue>
<required>true</required>
<description>Locale to use</description>
<options>
<option>
<value>de_DE</value>
<description>Use German locale</description>
</option>
</options>
</property>
</properties>
Of course, Maven should display an error if a required variable is
missing. And it would be nice to have "help:describe-properties"...
Regards,
Jochen
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RE: Re: Proposal: Required declaration of properties in pom.xml
Posted by "Brian E. Fox" <br...@reply.infinity.nu>.
I think almost of the required functionality of this proposal can be
achieved using the latest enforcer release. The requireProperty[1] rule
can check if a property is set and optionally regex the value. There is
also a beanShell[2] rule that allows similar checks.
The same reasons[3] we decided to make a plugin instead of modifying the
<prerequisites> tag apply here.
[1]
http://maven.apache.org/plugins/maven-enforcer-plugin/rules/requirePrope
rty.html
[2]
http://maven.apache.org/plugins/maven-enforcer-plugin/rules/evaluateBean
shell.html
[3]
http://www.nabble.com/Control-of-maven-using-prerequisites-tf3231437s177
.html#a8979318
-----Original Message-----
From: news [mailto:news@sea.gmane.org] On Behalf Of Jochen Kuhnle
Sent: Thursday, July 12, 2007 5:57 AM
To: dev@maven.apache.org
Subject: Re: Proposal: Required declaration of properties in pom.xml
On 2007-07-10 13:04:50 +0200, Kenney Westerhof <ke...@apache.org> said:
>
>>> currently, Maven does not require declaration of properties used in
the
>>> pom, you just use them anywhere you like. Usually, if a property is
>>> missing, bad things tend to happen because it is replaced with the
>>> string "null". On a good day, resources from
"translations-null-null"
>
> When/where is it null?
Just an example. What I was trying to say is that if a required
property is missing, and the developer forgot to set a default, the
build will do unexpected things. Mostly happens to me though when build
paths depend on properties.
>
>>> aren't included in the build, on bad days it's worse... And when you
>>> find the missing property in a pom you haven't written, you have to
>>> figure out what "${lopt}" means and what its legal values are...
>
> True, but proper defaults should be specified in the pom itself using
> the normal properties tag. Commandline, profiles, and settings
> can override these. A pom should just work out of the box. If you
> want to customize it you'll have to read the pom to see what can be
customized;
> there should be a readme or documentation in the pom for that.
It may not be possible to set a proper default in the pom, because the
property depends on the user's system or organization. Examples are a
deployment location or the local company repository. I think it is
better to specify that such a value is required (and tell the user
about this) than to put a default in there that the user surely cannot
work with.
I first proposed to make the declaration mandatory, so the
specification of proper defaults would be required, instead of optional
and error-prone. I forgot about plugins... So the proposal should be
downscaled to "required specification if the property is referenced in
the pom.xml in any way". This would enforce the "working out of the
box" of the pom, and people know where to look for the property
documentation. In addition, having a property specification allows for
additional nice things, e.g. "mvn -interactive", promping you for the
options.
Commandline, profiles and settings still can override these, but if the
property is fully specified, only legal values can be used, preventing
unexpected behaviour.
>
> There's lots of cases where properties are used - pom interpolation,
> plugin configuration, filtering.. which one are you talking about?
All properties referenced in the pom.xml
>
> For pom interpolation, you may not always want properties evaluated.
> In any case, if the property can't be evaluated, the ${expression} is
> left intact. So the null case doesn't apply here..
>
> For plugin configuration, you cannot possibly list all properties for
all
> plugins out there.
>
> For filtering, you may just want to print a warning or fail; this
could
> be configured in the resources plugin.
>
> So how/when do you get the 'translations-null-null' problem exactly?
>
> I don't like the proposal as it's way too verbose
The minimal specification would only be
<property>
<name>xyz</name>
<value>123</value>
</property>
It's a bit more verbose than the current form, but all in all, poms are
not known for their brevity ;-)
> and as others have said
> only fixes a small set of problems you may have, but doesn't cover all
> cases.
In my experience, this these are the problems that occur the most. Of
course, this observation is not gerneralizable. However, I think that
specifying what you use is a good principle, and property handling
seems an odd case in the "formalize-everything-you-can" pom format.
True, the plugin case cannot be handled, since you never know what a
plugin does, so this should be outside of the scope of the proposal. If
a plugin is missing a required property, it would be the job of the
plugin to complain.
As a sidetrack, maybe there is a better way to configure plugins than
properties. From a plugin developer standpoint, it seems a bit
redundant to do @parameter expression="${myproperty}" in many places
just to make a plugin parameter configurable from the command line or
settings.xml. From a user standpoint "--test:skip" would be nicer than
"-Dmaven.test.skip" (although I guess that every Maven user can type
the latter very fast :-).
>
> There's an issue out there to make all property
references/declarations
> in the pom the same, preferrably <propname>value</propname>.
> Perhaps a '<propertyManagement>' section is more appropriate? :)
I'll update the proposal. Thanks for the comments.
Regards,
Jochen
>
>>>
>>> So instead typing
>>>
>>> <properties>
>>> <lopt>en_US</lopt>
>>> </properties>
>>>
>>> this proposal wants you to write
>>>
>>> <properties>
>>> <property>
>>> <name>lopt</name>
>>> <defaultValue>en_US</defaultValue>
>>> <required>true</required>
>>> <description>Locale to use</description>
>>> <options>
>>> <option>
>>> <value>de_DE</value>
>>> <description>Use German locale</description>
>>> </option>
>>> </options>
>>> </property>
>>> </properties>
>
> This is rather verbose. Do you really want to list all locales in this
case?
>
>>>
>>> Of course, Maven should display an error if a required variable is
>>> missing. And it would be nice to have "help:describe-properties"...
>
> -- Kenney
>
>
>>>
>>> Regards,
>>> Jochen
>>>
>>>
>>>
>>>
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>>> For additional commands, e-mail: dev-help@maven.apache.org
>>>
>>
>>
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Re: Proposal: Required declaration of properties in pom.xml
Posted by Jochen Kuhnle <jo...@kuhnle.net>.
On 2007-07-10 13:04:50 +0200, Kenney Westerhof <ke...@apache.org> said:
>
>>> currently, Maven does not require declaration of properties used in the
>>> pom, you just use them anywhere you like. Usually, if a property is
>>> missing, bad things tend to happen because it is replaced with the
>>> string "null". On a good day, resources from "translations-null-null"
>
> When/where is it null?
Just an example. What I was trying to say is that if a required
property is missing, and the developer forgot to set a default, the
build will do unexpected things. Mostly happens to me though when build
paths depend on properties.
>
>>> aren't included in the build, on bad days it's worse... And when you
>>> find the missing property in a pom you haven't written, you have to
>>> figure out what "${lopt}" means and what its legal values are...
>
> True, but proper defaults should be specified in the pom itself using
> the normal properties tag. Commandline, profiles, and settings
> can override these. A pom should just work out of the box. If you
> want to customize it you'll have to read the pom to see what can be customized;
> there should be a readme or documentation in the pom for that.
It may not be possible to set a proper default in the pom, because the
property depends on the user's system or organization. Examples are a
deployment location or the local company repository. I think it is
better to specify that such a value is required (and tell the user
about this) than to put a default in there that the user surely cannot
work with.
I first proposed to make the declaration mandatory, so the
specification of proper defaults would be required, instead of optional
and error-prone. I forgot about plugins... So the proposal should be
downscaled to "required specification if the property is referenced in
the pom.xml in any way". This would enforce the "working out of the
box" of the pom, and people know where to look for the property
documentation. In addition, having a property specification allows for
additional nice things, e.g. "mvn -interactive", promping you for the
options.
Commandline, profiles and settings still can override these, but if the
property is fully specified, only legal values can be used, preventing
unexpected behaviour.
>
> There's lots of cases where properties are used - pom interpolation,
> plugin configuration, filtering.. which one are you talking about?
All properties referenced in the pom.xml
>
> For pom interpolation, you may not always want properties evaluated.
> In any case, if the property can't be evaluated, the ${expression} is
> left intact. So the null case doesn't apply here..
>
> For plugin configuration, you cannot possibly list all properties for all
> plugins out there.
>
> For filtering, you may just want to print a warning or fail; this could
> be configured in the resources plugin.
>
> So how/when do you get the 'translations-null-null' problem exactly?
>
> I don't like the proposal as it's way too verbose
The minimal specification would only be
<property>
<name>xyz</name>
<value>123</value>
</property>
It's a bit more verbose than the current form, but all in all, poms are
not known for their brevity ;-)
> and as others have said
> only fixes a small set of problems you may have, but doesn't cover all
> cases.
In my experience, this these are the problems that occur the most. Of
course, this observation is not gerneralizable. However, I think that
specifying what you use is a good principle, and property handling
seems an odd case in the "formalize-everything-you-can" pom format.
True, the plugin case cannot be handled, since you never know what a
plugin does, so this should be outside of the scope of the proposal. If
a plugin is missing a required property, it would be the job of the
plugin to complain.
As a sidetrack, maybe there is a better way to configure plugins than
properties. From a plugin developer standpoint, it seems a bit
redundant to do @parameter expression="${myproperty}" in many places
just to make a plugin parameter configurable from the command line or
settings.xml. From a user standpoint "--test:skip" would be nicer than
"-Dmaven.test.skip" (although I guess that every Maven user can type
the latter very fast :-).
>
> There's an issue out there to make all property references/declarations
> in the pom the same, preferrably <propname>value</propname>.
> Perhaps a '<propertyManagement>' section is more appropriate? :)
I'll update the proposal. Thanks for the comments.
Regards,
Jochen
>
>>>
>>> So instead typing
>>>
>>> <properties>
>>> <lopt>en_US</lopt>
>>> </properties>
>>>
>>> this proposal wants you to write
>>>
>>> <properties>
>>> <property>
>>> <name>lopt</name>
>>> <defaultValue>en_US</defaultValue>
>>> <required>true</required>
>>> <description>Locale to use</description>
>>> <options>
>>> <option>
>>> <value>de_DE</value>
>>> <description>Use German locale</description>
>>> </option>
>>> </options>
>>> </property>
>>> </properties>
>
> This is rather verbose. Do you really want to list all locales in this case?
>
>>>
>>> Of course, Maven should display an error if a required variable is
>>> missing. And it would be nice to have "help:describe-properties"...
>
> -- Kenney
>
>
>>>
>>> Regards,
>>> Jochen
>>>
>>>
>>>
>>> ---------------------------------------------------------------------
>>> To unsubscribe, e-mail: dev-unsubscribe@maven.apache.org
>>> For additional commands, e-mail: dev-help@maven.apache.org
>>>
>>
>>
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Re: Proposal: Required declaration of properties in pom.xml
Posted by Kenney Westerhof <ke...@apache.org>.
> Jochen Kuhnle wrote:
>> Hi,
>>
>> currently, Maven does not require declaration of properties used in
>> the pom, you just use them anywhere you like. Usually, if a property
>> is missing, bad things tend to happen because it is replaced with the
>> string "null". On a good day, resources from "translations-null-null"
When/where is it null?
>> aren't included in the build, on bad days it's worse... And when you
>> find the missing property in a pom you haven't written, you have to
>> figure out what "${lopt}" means and what its legal values are...
True, but proper defaults should be specified in the pom itself using
the normal properties tag. Commandline, profiles, and settings
can override these. A pom should just work out of the box. If you
want to customize it you'll have to read the pom to see what can be customized;
there should be a readme or documentation in the pom for that.
There's lots of cases where properties are used - pom interpolation,
plugin configuration, filtering.. which one are you talking about?
For pom interpolation, you may not always want properties evaluated.
In any case, if the property can't be evaluated, the ${expression} is
left intact. So the null case doesn't apply here..
For plugin configuration, you cannot possibly list all properties for all
plugins out there.
For filtering, you may just want to print a warning or fail; this could
be configured in the resources plugin.
So how/when do you get the 'translations-null-null' problem exactly?
I don't like the proposal as it's way too verbose and as others have said
only fixes a small set of problems you may have, but doesn't cover all
cases.
There's an issue out there to make all property references/declarations
in the pom the same, preferrably <propname>value</propname>.
Perhaps a '<propertyManagement>' section is more appropriate? :)
>>
>> So instead typing
>>
>> <properties>
>> <lopt>en_US</lopt>
>> </properties>
>>
>> this proposal wants you to write
>>
>> <properties>
>> <property>
>> <name>lopt</name>
>> <defaultValue>en_US</defaultValue>
>> <required>true</required>
>> <description>Locale to use</description>
>> <options>
>> <option>
>> <value>de_DE</value>
>> <description>Use German locale</description>
>> </option>
>> </options>
>> </property>
>> </properties>
This is rather verbose. Do you really want to list all locales in this case?
>>
>> Of course, Maven should display an error if a required variable is
>> missing. And it would be nice to have "help:describe-properties"...
-- Kenney
>>
>> Regards,
>> Jochen
>>
>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: dev-unsubscribe@maven.apache.org
>> For additional commands, e-mail: dev-help@maven.apache.org
>>
>
>
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Re: Proposal: Required declaration of properties in pom.xml
Posted by Jason van Zyl <ja...@maven.org>.
Thanks for putting the proposals in the wiki. Now with a simple page
watch anyone can be notified when new proposals are added.
On 4 Jul 07, at 12:00 AM 4 Jul 07, Jochen Kuhnle wrote:
> On 2007-07-03 19:30:33 +0200, "Jochen Wiedmann"
> <jo...@gmail.com> said:
>
>>> currently, Maven does not require declaration of properties used in
>>> the pom, you just use them anywhere you like.
>> Don't like the proposal. It is suitable for 90% of all cases, but
>> doesn't match the cases where you don't know the possible property
>> set
>> in advance. (For example, if you use something like "prop.1=...,
>> prop.2=...", or in the case of log4j.properties with "propList=a,b,c
>> ... prop.a.X=..., prop.b.X=..., prop.c.Y=....)
>
> Can properties be used in this way in the pom.xml? Since the pom
> language has no control structures like loops etc., it should be
> hard to use lists. Could you give an example, maybe we can find a
> way to change the proposal to suit both needs?
>
> Regards,
> Jochen
>
>
>
>
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> For additional commands, e-mail: dev-help@maven.apache.org
>
>
Thanks,
Jason
----------------------------------------------------------
Jason van Zyl
Founder and PMC Chair, Apache Maven
jason at sonatype dot com
----------------------------------------------------------
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Re: Proposal: Required declaration of properties in pom.xml
Posted by Mark Hobson <ma...@gmail.com>.
How about simply using XSD for validation and accepting namespaced properties?
Mark
On 04/07/07, Jochen Kuhnle <jo...@kuhnle.net> wrote:
> On 2007-07-04 09:04:10 +0200, "Jochen Wiedmann"
> <jo...@gmail.com> said:
>
> > On 7/4/07, Jochen Kuhnle <jo...@kuhnle.net> wrote:
> >
> >> Can properties be used in this way in the pom.xml? Since the pom
> >> language has no control structures like loops etc., it should be hard
> >> to use lists. Could you give an example, maybe we can find a way to
> >> change the proposal to suit both needs?
> >
> > They cannot be used that way in the pom.xml, but by plugins.
>
> Ok. If we check during pom interpolation, this should work. With the
> proposal, it is still possible to set any variable to any value in the
> pom. If option values are specified, they are validated, if not, any
> value is valid. System or "-D" properties would be set for the plugins,
> but only validated if they are used in the pom.
>
> Regards,
> Jochen
>
>
>
> ---------------------------------------------------------------------
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> For additional commands, e-mail: dev-help@maven.apache.org
>
>
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Re: Proposal: Required declaration of properties in pom.xml
Posted by Jochen Kuhnle <jo...@kuhnle.net>.
On 2007-07-04 09:04:10 +0200, "Jochen Wiedmann"
<jo...@gmail.com> said:
> On 7/4/07, Jochen Kuhnle <jo...@kuhnle.net> wrote:
>
>> Can properties be used in this way in the pom.xml? Since the pom
>> language has no control structures like loops etc., it should be hard
>> to use lists. Could you give an example, maybe we can find a way to
>> change the proposal to suit both needs?
>
> They cannot be used that way in the pom.xml, but by plugins.
Ok. If we check during pom interpolation, this should work. With the
proposal, it is still possible to set any variable to any value in the
pom. If option values are specified, they are validated, if not, any
value is valid. System or "-D" properties would be set for the plugins,
but only validated if they are used in the pom.
Regards,
Jochen
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Re: Proposal: Required declaration of properties in pom.xml
Posted by Jochen Wiedmann <jo...@gmail.com>.
On 7/4/07, Jochen Kuhnle <jo...@kuhnle.net> wrote:
> Can properties be used in this way in the pom.xml? Since the pom
> language has no control structures like loops etc., it should be hard
> to use lists. Could you give an example, maybe we can find a way to
> change the proposal to suit both needs?
They cannot be used that way in the pom.xml, but by plugins.
--
"Besides, manipulating elections is under penalty of law, resulting in
a preventative effect against manipulating elections.
The german government justifying the use of electronic voting machines
and obviously believing that we don't need a police, because all
illegal actions are forbidden.
http://dip.bundestag.de/btd/16/051/1605194.pdf
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Re: Proposal: Required declaration of properties in pom.xml
Posted by Jochen Kuhnle <jo...@kuhnle.net>.
On 2007-07-03 19:30:33 +0200, "Jochen Wiedmann"
<jo...@gmail.com> said:
>> currently, Maven does not require declaration of properties used in
>> the pom, you just use them anywhere you like.
>
> Don't like the proposal. It is suitable for 90% of all cases, but
> doesn't match the cases where you don't know the possible property set
> in advance. (For example, if you use something like "prop.1=...,
> prop.2=...", or in the case of log4j.properties with "propList=a,b,c
> ... prop.a.X=..., prop.b.X=..., prop.c.Y=....)
Can properties be used in this way in the pom.xml? Since the pom
language has no control structures like loops etc., it should be hard
to use lists. Could you give an example, maybe we can find a way to
change the proposal to suit both needs?
Regards,
Jochen
---------------------------------------------------------------------
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Re: Proposal: Required declaration of properties in pom.xml
Posted by Jochen Wiedmann <jo...@gmail.com>.
> currently, Maven does not require declaration of properties used in
> the pom, you just use them anywhere you like.
Don't like the proposal. It is suitable for 90% of all cases, but
doesn't match the cases where you don't know the possible property set
in advance. (For example, if you use something like "prop.1=...,
prop.2=...", or in the case of log4j.properties with "propList=a,b,c
... prop.a.X=..., prop.b.X=..., prop.c.Y=....)
--
"Besides, manipulating elections is under penalty of law, resulting in
a preventative effect against manipulating elections.
The german government justifying the use of electronic voting machines
and obviously believing that we don't need a police, because all
illegal actions are forbidden.
http://dip.bundestag.de/btd/16/051/1605194.pdf
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Re: Proposal: Required declaration of properties in pom.xml
Posted by Paul Gier <pg...@redhat.com>.
+1
I think this is a good idea. The next release of the enforcer plugin
(http://maven.apache.org/plugins/maven-enforcer-plugin/) will have some
property verification features, but it would be nice to add the property
verification stuff directly to the pom.
Jochen Kuhnle wrote:
> Hi,
>
> currently, Maven does not require declaration of properties used in
> the pom, you just use them anywhere you like. Usually, if a property
> is missing, bad things tend to happen because it is replaced with the
> string "null". On a good day, resources from "translations-null-null"
> aren't included in the build, on bad days it's worse... And when you
> find the missing property in a pom you haven't written, you have to
> figure out what "${lopt}" means and what its legal values are...
>
> So instead typing
>
> <properties>
> <lopt>en_US</lopt>
> </properties>
>
> this proposal wants you to write
>
> <properties>
> <property>
> <name>lopt</name>
> <defaultValue>en_US</defaultValue>
> <required>true</required>
> <description>Locale to use</description>
> <options>
> <option>
> <value>de_DE</value>
> <description>Use German locale</description>
> </option>
> </options>
> </property>
> </properties>
>
> Of course, Maven should display an error if a required variable is
> missing. And it would be nice to have "help:describe-properties"...
>
> Regards,
> Jochen
>
>
>
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>
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Re: Proposal: Required declaration of properties in pom.xml
Posted by Jochen Kuhnle <jo...@kuhnle.net>.
On 2007-07-03 18:35:01 +0200, "Brian E. Fox" <br...@reply.infinity.nu> said:
>
> Is this a proposal on the wiki that is being summarized, or the whole =
Just first thoughts... I'm relatively new to this, so any help or
comments are welcome.
> thing? If it's the whole thing, I have some questions:
> 1. Why a default value and a required flag? If it's required, when would =
> the default be used?
Either can be omitted. You're right that specifying both at the same
time does not make sense. It is an error if a property is unspecified
and required, and there is no default value. If a property is
unspecified and has a default value, it is used.
> 2. How is the option value activated? Is this implying that these are =
> the only valid values and an error should be thrown if it doesn't match?
If specified, option values are the only valid ones.
> 3. Can values be specified using a regex or wildcards?
That would sure be nice.
> =20
> (btw most of this can be done using the snapshot enforcer with the =
> requireProperty rule)
Using the enforcer plugin is optional, while the proposal would force
people to declare their variables.
Regards,
Jochen
>
> ________________________________
>
> From: news on behalf of Jochen Kuhnle
> Sent: Tue 7/3/2007 12:05 PM
> To: dev@maven.apache.org
> Subject: Proposal: Required declaration of properties in pom.xml
>
>
>
> Hi,
>
> currently, Maven does not require declaration of properties used in the
> pom, you just use them anywhere you like. Usually, if a property is
> missing, bad things tend to happen because it is replaced with the
> string "null". On a good day, resources from "translations-null-null"
> aren't included in the build, on bad days it's worse... And when you
> find the missing property in a pom you haven't written, you have to
> figure out what "${lopt}" means and what its legal values are...
>
> So instead typing
>
> <properties>
> <lopt>en_US</lopt>
> </properties>
>
> this proposal wants you to write
>
> <properties>
> <property>
> <name>lopt</name>
> <defaultValue>en_US</defaultValue>
> <required>true</required>
> <description>Locale to use</description>
> <options>
> <option>
> <value>de_DE</value>
> <description>Use German =
> locale</description>
> </option>
> </options>
> </property>
> </properties>
>
> Of course, Maven should display an error if a required variable is
> missing. And it would be nice to have "help:describe-properties"...
>
> Regards,
> Jochen
>
>
>
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RE: Proposal: Required declaration of properties in pom.xml
Posted by "Brian E. Fox" <br...@reply.infinity.nu>.
Is this a proposal on the wiki that is being summarized, or the whole thing? If it's the whole thing, I have some questions:
1. Why a default value and a required flag? If it's required, when would the default be used?
2. How is the option value activated? Is this implying that these are the only valid values and an error should be thrown if it doesn't match?
3. Can values be specified using a regex or wildcards?
(btw most of this can be done using the snapshot enforcer with the requireProperty rule)
________________________________
From: news on behalf of Jochen Kuhnle
Sent: Tue 7/3/2007 12:05 PM
To: dev@maven.apache.org
Subject: Proposal: Required declaration of properties in pom.xml
Hi,
currently, Maven does not require declaration of properties used in the
pom, you just use them anywhere you like. Usually, if a property is
missing, bad things tend to happen because it is replaced with the
string "null". On a good day, resources from "translations-null-null"
aren't included in the build, on bad days it's worse... And when you
find the missing property in a pom you haven't written, you have to
figure out what "${lopt}" means and what its legal values are...
So instead typing
<properties>
<lopt>en_US</lopt>
</properties>
this proposal wants you to write
<properties>
<property>
<name>lopt</name>
<defaultValue>en_US</defaultValue>
<required>true</required>
<description>Locale to use</description>
<options>
<option>
<value>de_DE</value>
<description>Use German locale</description>
</option>
</options>
</property>
</properties>
Of course, Maven should display an error if a required variable is
missing. And it would be nice to have "help:describe-properties"...
Regards,
Jochen
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