placholder_hightlight.java

public String getPlaceholderText(@NotNull final ASTNode node) {
    ...
        
    if (psi instanceof DLanguageBlockStatement) {
        final DLanguageBlockStatement block = (DLanguageBlockStatement) psi;
        final PsiElement inner = getInnerStatementBlockForDisplayInPlaceholder(block);

        if (inner != null) {
            return "{ " + inner.getText().trim() + " }";
        } else {
            return "{...}";
        }
    }
    ...
}

private PsiElement getInnerStatementBlockForDisplayInPlaceholder(final DLanguageBlockStatement blockStatement) {
    if (blockStatement.getChildren().length == 0)
        return null;

    final PsiElement inner = blockStatement.getChildren()[0];
    final String innerText = inner.getText();

    if (innerText.contains("\n") || innerText.contains("\r") ||
        inner.getTextLength() > MAX_BODY_LENGTH_TO_DISPLAY)
    {
        return null;
    }

    return inner;
}