Fixed false error thrown if parent pom version uses variable

[Achal1607]

• When parent pom uses variable for defining version:
  

• When child pom uses variable again for the parent version then it throws false error:
  

So, fixed the above mentioned issue in this PR.
Refer for more info: oracle/javavscode#95

[mbien]

good fix!

[Achal1607]

I don't know why this test is failing, I haven't changed anything in context of this test.

[mbien]

happens sometimes, I restarted it.

[ebarboni]

Hi sorry to join late. But ${revision} is reserved word, if ${my-revision} were used it's should warn that version is incorrect

${revision}, ${changelist}, and ${sha1} are the reserved versions as per https://maven.apache.org/docs/3.2.1/release-notes.html

[Achal1607]

Oh sorry I didn't knew of this. So, anything apart from ${revision}, ${changelist}, and ${sha1} cannot be used as expression in version field?

[ebarboni]

I'm not aware of others 'keyword' but if you use a random properties you will have warning

Some problems were encountered while building the effective model for com.mycompany:mavenproject2:pom:${sha1aa}
'version' contains an expression but should be a constant. @ line 6, column 14

It is highly recommended to fix these problems because they threaten the stability of your build.

For this reason, future Maven versions might no longer support building such malformed projects.

[neilcsmith-net]

Yes, valid properties from here I think - https://github.com/apache/maven/blob/master/maven-model-builder/src/main/java/org/apache/maven/model/interpolation/DefaultModelVersionProcessor.java#L43 Not sure best way to access that, or whether to code in the allowed values?

[ebarboni]

maybe hardcoded + link to the github :p

[Achal1607]

• When child pom uses variable again for the parent version then it throws false error:
  

So, fixed the above mentioned issue in this PR. Refer for more info: oracle/javavscode#95

The above error is anyways misleading for any case. So, imo we can keep the change that is done in this PR as it is.
Since, warning is already shown if something other than these 3 keywords are used in the version tag, isn't it correct?