How do I add a completion contributor for a composite element?

Created December 20, 2019 16:18

I need to add additional entries to the completion dialog for method references (e.g. Objects::toString). The article says that I need to use withParent or withSuperParent for composite elements, but none of them works.

PSIViewer says that PsiMethodReferenceExpression is direct parent of the toString identifier, so when I define the following element pattern

 PlatformPatterns.psiElement(JavaTokenType.IDENTIFIER).withParent(PsiMethodReferenceExpression.class)

 PlatformPatterns.psiElement(PsiIdentifier.class).withParent(PsiMethodReferenceExpression.class)

it does not work. If I remove the .withParent(...) part the additional entries in the completion dialog are present everywhere.

Notice: For the specified element pattern the entries appears in the completion dialog for Objects:: (after the double colon)

The completion contribution class looks like this:

public class MethodReferenceCompletion extends CompletionContributor  {

    public MethodReferenceCompletion() {

        extend(
                CompletionType.BASIC,
                PlatformPatterns.psiElement(PsiIdentifier.class).withParent(PsiMethodReferenceExpression.class),
                new MethodReferenceCompletionProvider()
        );
    }
}

1 comment

Nikita Eshkeev

Created December 21, 2019 10:56

I came up with a partial solution, which covers the following patterns (adds entries to the completion dialog after a method reference name):

```
Object::new.
```
```
(Object::new).
```
```
Collections::<Integer>sort.
```

But the solution also covers the following false-positive pattern:

System.

because PsiMethodReferenceExpression happens to inherit PsiReferenceExpression

How can I simplify it and eliminate the false-positive case?

The current version of the class:

public class MethodReferenceCompletion extends CompletionContributor  {

    public MethodReferenceCompletion() {

        final PsiElementPattern.Capture<PsiElement> methodLocation = psiElement()
                .afterLeafSkipping(
                        psiElement()
                                .withParent(PsiMethodReferenceExpression.class)
                                .withText("::")
                                .afterSibling(psiElement(PsiReferenceParameterList.class)),
                        psiElement()
                );
        final PsiElementPattern.Capture<PsiElement> doubleColumnLocationAfter = psiElement().afterLeaf("::");
        final PsiElementPattern.Capture<PsiElement> parameterListLocationAfter = psiElement().afterLeaf("<", ">");
        final PsiElementPattern.Capture<PsiElement> parameterListLocationBefore = psiElement().beforeLeaf("<", ">");
        final PsiElementPattern.Capture<PsiElement> classLocation = psiElement().beforeLeaf(psiElement().withText("::"));
        final PsiElementPattern.Capture<PsiElement> firstParenthesisLocation = psiElement().beforeLeafSkipping(psiElement().withText("::"), psiElement().beforeLeaf("("));
        final PsiElementPattern.Capture<PsiElement> place = methodLocation
                .andNot(firstParenthesisLocation)
                .andNot(classLocation)
                .andNot(doubleColumnLocationAfter)
                .andNot(parameterListLocationAfter)
                .andNot(parameterListLocationBefore)
                ;
        extend(
                CompletionType.BASIC,
                place
                ,new MethodReferenceCompletionProvider()
        );
    }
}

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