Grails: autocompletion of resource bundle keys in <g:message/> tags doesn't find entries from plugin dependencies

There is a problem with the autocompletion of resource bundle keys inside .gsp files in a grails project: when I have a main project, which depends on a grails plugin project, the resource bundles inside the plugin are not considered. Autocompletion only finds the resource keys inside the same project, but not the ones in the plugin dependency.

This also affects the code highlighting inside .gsp files.
In the following snippet, IntelliJ will mark the key "my.example.key" as "Cannot resolve property key", when the key is inside the plugin project:
```

```
However, if I use groovy expressions instead of the tag syntax, the autocompletion works fine and IntelliJ also doesn't report an error:
```
${message(code: 'default.search.noResults')}
```
**I have the following project setup:**

- gradle multi-project build
- a grails web subproject
- a grails plugin subproject
- the web project depends on the plugin project
- both grails projects have resource bundles

I observed this in IntelliJ 2017.1 using different grails versions (3.2.9, 3.1.10).

---

*Imported from [IDEA-174720](https://youtrack.jetbrains.com/issue/IDEA-174720) · Type: Bug · Votes: 0*
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Reproduce the issue in IntelliJ IDEA 2017.1 with the described Gradle multi-project setup: a Grails web project depending on a Grails plugin project, each with resource bundles. Trace how keys are resolved versus Groovy-expression message calls; done means plugin dependency keys autocomplete and no longer show an unresolved-property highlight in GSP files.

Written by the indexing model from the issue text.