```
from employees | keep * | mv_expand first_name
```

throws UnresolvedException:

```
org.elasticsearch.xpack.ql.capabilities.UnresolvedException: Invalid call to attribute on an unresolved object ?*
        at org.elasticsearch.xpack.ql.expression.UnresolvedNamedExpression.toAttribute(UnresolvedNamedExpression.java:44)
        at org.elasticsearch.xpack.ql.expression.Expressions.asAttributes(Expressions.java:40)
        at org.elasticsearch.xpack.ql.plan.logical.Project.output(Project.java:62)
        at org.elasticsearch.xpack.esql.plan.logical.MvExpand.<init>(MvExpand.java:31)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.lambda$visitMvExpandCommand$3(LogicalPlanBuilder.java:154)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.visitCompositeQuery(LogicalPlanBuilder.java:89)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.visitCompositeQuery(LogicalPlanBuilder.java:66)
        at org.elasticsearch.xpack.esql.parser.EsqlBaseParser$CompositeQueryContext.accept(EsqlBaseParser.java:232)
        at org.elasticsearch.xpack.ql.parser.ParserUtils.typedParsing(ParserUtils.java:51)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.plan(LogicalPlanBuilder.java:73)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.visitSingleStatement(LogicalPlanBuilder.java:82)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.visitSingleStatement(LogicalPlanBuilder.java:66)
        at org.elasticsearch.xpack.esql.parser.EsqlBaseParser$SingleStatementContext.accept(EsqlBaseParser.java:169)
```

The problem is that MV_EXPAND tries to pre-calculate the output too early, when the resolution did not happen yet.
x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/parser/StatementParserTests.java
}
    private static Literal literalUnsignedLongs(String... ulongs) {
        return new Literal(EMPTY, Arrays.stream(ulongs).map(s -> asLongUnsigned(new BigInteger(s))).toList(), DataTypes.UNSIGNED_LONG);
    }
    private static Literal literalBoolean(boolean b) {
        return new Literal(EMPTY, b, DataTypes.BOOLEAN);
    }
    private static Literal literalBooleans(boolean... booleans) {
        List<Boolean> v = new ArrayList<>(booleans.length);
        for (boolean b : booleans) {
            v.add(b);
        }
        return new Literal(EMPTY, v, DataTypes.BOOLEAN);
    }
    private static Literal literalString(String s) {
        return new Literal(EMPTY, s, DataTypes.KEYWORD);
    }
    private static Literal literalStrings(String... strings) {
        return new Literal(EMPTY, Arrays.asList(strings), DataTypes.KEYWORD);
    }
    private void expectError(String query, String errorMessage) {
        ParsingException e = expectThrows(ParsingException.class, "Expected syntax error for " + query, () -> statement(query));
        assertThat(e.getMessage(), containsString(errorMessage));
    }
    private void expectError(String query, List<TypedParamValue> params, String errorMessage) {
        ParsingException e = expectThrows(ParsingException.class, "Expected syntax error for " + query, () -> statement(query, params));
        assertThat(e.getMessage(), containsString(errorMessage));
    }
}