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https://issues.apache.org/jira/browse/IVY-871?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16268633#comment-16268633
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jaikiran pai edited comment on IVY-871 at 11/28/17 12:01 PM:
-------------------------------------------------------------
[~martinm82], thank you for adding those details. I have to admit, the
documentation around this matcher needs a bit more work to make it clear what
it does. I had to go back and check the code to understand what it's doing.
In short, what it does is (using your snippet as an example), when it sees that
there's a matcher configured for something called {{latestRel}}, during
dependency resolution, it checks if the revision being asked for, via a
dependency matches the {{revision}} attribute of the {{matcher}} configured. If
it does, then it uses that configured matcher to see if it can resolve a
version for this dependency. While doing so, the matcher can (optionally) be
passed "arguments", a list of which is configured on the matcher through the
{{args}} attribute. So in your case, you are expecting {{release}} as an
argument to the matcher. The dependency (in your ivy.xml) passes a value for
this argument. In your case, you are passing {{17.4}} as an argument to that
matcher. The matcher can be configured (as you have done in your case) to use
the (substituted value) of the argument(s) in the {{pattern}} attribute. So in
your case, this now translates to the {{pattern}} attribute value being
{{\d+\.\d+\.\d+-17.4\.*}}.
This value of the {{pattern}} attribute is then used for matching/resolving
the versions for the dependency. How that {{pattern}} value is semantically
interpreted is decided by the {{matcher}} attribute and in this case you have
configured it to be a {{regex}}. So your pattern value
{{\d+\.\d+\.\d+-17.4\.*}} will now be used as a regular expression while
evaluating the dependency version {{latestRel(17.4)}} asked for as an ivy
dependency. I hope that makes it clear on what it does. I'll add this (with
some changes maybe) to our documentation this week.
was (Author: jaikiran):
[~martinm82], thank you for adding those details. I have to admit, the
documentation around this matcher needs a bit more work to make it clear what
it does. I had to go back and check the code to understand what it's doing.
In short, what it does is (using your snippet as an example), when it sees that
there's a matcher configured for something called {{latestRel}}, during
dependency resolution, it checks if the revision being asked for, via a
dependency matches the {{revision}} attribute of the {{matcher}} configured. If
it does, then it uses that configured matcher to see if it can resolve a
version for this dependency. While doing so, the matcher can (optionally) be
passed "arguments", a list of which is configured on the matcher through the
{{args}} attribute. So in your case, you are expecting {{release}} as an
argument to the matcher. The dependency (in your ivy.xml) passes a value for
this argument. In your case, you are passing {{17.4}} as an argument to that
matcher. The matcher can be configured (as you have done in your case) to use
the (substituted value) of the argument(s) in the {{pattern}} attribute. So in
your case, this now translates to the {{pattern}} attribute value being
{{\d+\.\d+\.\d+-17.4\.*}}. This value of the {{pattern}} attribute is then used
for matching/resolving the versions for the dependency. How that {{pattern}}
value is semantically interpreted is decided by the {{matcher}} attribute and
in this case you have configured it to be a {{regex}}. So your pattern value
{{\d+\.\d+\.\d+-17.4\.*}} will now be used as a regular expression while
evaluating the dependency version {{latestRel(17.4)}} asked for as an ivy
dependency. I hope that makes it clear on what it does. I'll add this (with
some changes maybe) to our documentation this week.
> test and document PatternVersionMatcher
> ---------------------------------------
>
> Key: IVY-871
> URL: https://issues.apache.org/jira/browse/IVY-871
> Project: Ivy
> Issue Type: Improvement
> Components: Core
> Reporter: Xavier Hanin
> Assignee: Maarten Coene
> Fix For: 2.1.0-RC2
>
> Attachments: patch.txt
>
>
> There is a powerful version matcher in Ivy code base called
> PatternVersionMatcher. Unfortunately, this matcher is not documented, not
> tested, and not declared in the default typedef.properties. Nobody remembers
> where it comes from, but code analysis should be enough to understand how it
> works and what it can achieve.
> Here's what I understand from a quick analysis:
> {code:title=settings.xml}
> <pattern-vm>
> <match revision="micro" pattern="${major}\.${minor}\.\d+" args="major,
> minor" matcher="regexp" />
> </pattern-vm>
> {code}
> {code:title=ivy.xml}
> <dependency org="acme" name="foo" rev="micro(1, 3)" />
> {code}
> If I understand correctly the code, this will match any revision like
> 1.3.<any number>.
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