Add index name validation rule for empty index names

[craigtaverner]

In serverless there was a suppressed REST error with the following stacktrace:

java.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for length 0
at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:55)
at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:52)
at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:213)
at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:210)
at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:98)
at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:106)
at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:302)
at java.base/java.lang.String.checkIndex(String.java:4930) at java.base/java.lang.StringLatin1.charAt(StringLatin1.java:46)
at java.base/java.lang.String.charAt(String.java:1629)
at org.elasticsearch.server@9.0.0/org.elasticsearch.cluster.metadata.MetadataCreateIndexService.validateIndexOrAliasName(MetadataCreateIndexService.java:250)
at org.elasticsearch.xpack.esql.parser.IdentifierBuilder.validateIndexPattern(IdentifierBuilder.java:104)
at org.elasticsearch.xpack.esql.parser.IdentifierBuilder.lambda$visitIndexPattern$0(IdentifierBuilder.java:70)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1597)
at org.elasticsearch.xpack.esql.parser.IdentifierBuilder.visitIndexPattern(IdentifierBuilder.java:63)
at org.elasticsearch.xpack.esql.parser.ExpressionBuilder.visitIndexPattern(ExpressionBuilder.java:92)
at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.visitFromCommand(LogicalPlanBuilder.java:260)
at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.visitFromCommand(LogicalPlanBuilder.java:88)
at org.elasticsearch.xpack.esql.parser.EsqlBaseParser$FromCommandContext.accept(EsqlBaseParser.java:2210)
at org.antlr.v4.runtime.tree.AbstractParseTreeVisitor.visitChildren(AbstractParseTreeVisitor.java:46)
at org.elasticsearch.xpack.esql.parser.EsqlBaseParserBaseVisitor.visitSourceCommand(EsqlBaseParserBaseVisitor.java:50)
...

Without knowing the original query, it is hard to know how this happened, but the underlying exception is being thrown because the index name being identified in the ES|QL parser is empty. The current index name validation rules do not consider this case, so we get a StringIndexOutOfBoundsException, but we can enhance the validation rules to at least throw the correct exception, in this case InvalidIndexNameException.

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[fang-xing-esql]

Thank you @craigtaverner, LGTM!

There are two types of index patterns, *- and -, that I can think of which can cause this error, and both of them are addressed in this PR. If we can have someone who is familiar with MetadataCreateIndexService.validateIndexOrAliasName to double check that will be great. I couldn't think of a reason that we should not make this change.

An alternative is to skip the call to MetadataCreateIndexService.validateIndexOrAliasName in IdentifierBuilder.validateIndexPattern if it is an empty index pattern, just in case it is not preferable to change MetadataCreateIndexService.validateIndexOrAliasName.

[costin]

Good catch - LGTM

[elasticsearchmachine]

💚 Backport successful

Status	Branch	Result
✅	8.x