LUCENE-9098 Report bad term for fuzzy query

When a fuzzy query encounters a term that is too complex, the exception
should report the term instead of a cryptic message about too many
states.

lucene/core/src/java/org/apache/lucene/search/FuzzyTermsEnum.java

@@ -37,6 +37,7 @@ import org.apache.lucene.util.UnicodeUtil;
 import org.apache.lucene.util.automaton.Automaton;
 import org.apache.lucene.util.automaton.CompiledAutomaton;
 import org.apache.lucene.util.automaton.LevenshteinAutomata;
+import org.apache.lucene.util.automaton.TooComplexToDeterminizeException;
 
 /** Subclass of TermsEnum for enumerating all terms that are similar
  * to the specified filter term.
@@ -131,7 +132,11 @@ public final class FuzzyTermsEnum extends BaseTermsEnum {
       prevAutomata = new CompiledAutomaton[maxEdits+1];
       Automaton[] automata = buildAutomata(termText, prefixLength, transpositions, maxEdits);
       for (int i = 0; i <= maxEdits; i++) {
-        prevAutomata[i] = new CompiledAutomaton(automata[i], true, false);
+        try {
+          prevAutomata[i] = new CompiledAutomaton(automata[i], true, false);
+        } catch (TooComplexToDeterminizeException e) {
+          throw new FuzzyTermsException(term.text(), e);
+        }
       }
       // first segment computes the automata, and we share with subsequent segments via this Attribute:
       dfaAtt.setAutomata(prevAutomata);
@@ -407,4 +412,15 @@ public final class FuzzyTermsEnum extends BaseTermsEnum {
       reflector.reflect(LevenshteinAutomataAttribute.class, "automata", automata);
     }
   }
+
+  /**
+   * Thrown to indicate that there was an issue creating a fuzzy query for a given term.
+   * Typically occurs with terms longer than 220 UTF-8 characters,
+   * but also possible with shorter terms consisting of UTF-32 code points.
+   */
+  public static class FuzzyTermsException extends RuntimeException {
+    private FuzzyTermsException(String term, Throwable cause) {
+      super("Term too complex: " + term, cause);
+    }
+  }
 }

lucene/core/src/test/org/apache/lucene/search/TestFuzzyQuery.java

@@ -25,6 +25,7 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
 
+import com.carrotsearch.randomizedtesting.RandomizedTest;
 import org.apache.lucene.analysis.MockAnalyzer;
 import org.apache.lucene.analysis.MockTokenizer;
 import org.apache.lucene.document.Document;
@@ -35,6 +36,8 @@ import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.MultiReader;
 import org.apache.lucene.index.RandomIndexWriter;
 import org.apache.lucene.index.Term;
+import org.apache.lucene.index.Terms;
+import org.apache.lucene.index.TermsEnum;
 import org.apache.lucene.search.BooleanClause.Occur;
 import org.apache.lucene.search.similarities.ClassicSimilarity;
 import org.apache.lucene.store.Directory;
@@ -43,6 +46,9 @@ import org.apache.lucene.util.IntsRef;
 import org.apache.lucene.util.LuceneTestCase;
 import org.apache.lucene.util.TestUtil;
 import org.apache.lucene.util.automaton.LevenshteinAutomata;
+import org.apache.lucene.util.automaton.Operations;
+
+import static org.hamcrest.CoreMatchers.containsString;
 
 /**
  * Tests {@link FuzzyQuery}.
@@ -492,7 +498,63 @@ public class TestFuzzyQuery extends LuceneTestCase {
     });
     assertTrue(expected.getMessage().contains("maxExpansions must be positive"));
   }
-  
+
+  public void testErrorMessage() {
+    // 45 states per vector from Lev2TParametricDescription
+    int length = (Operations.DEFAULT_MAX_DETERMINIZED_STATES / 45) + 10;
+
+    String value = RandomizedTest.randomRealisticUnicodeOfCodepointLength(length);
+    FuzzyTermsEnum.FuzzyTermsException expected = expectThrows(FuzzyTermsEnum.FuzzyTermsException.class, () -> {
+      new FuzzyQuery(new Term("field", value)).getTermsEnum(new Terms() {
+        @Override
+        public TermsEnum iterator() {
+          throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public long size() {
+          throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public long getSumTotalTermFreq() {
+          throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public long getSumDocFreq() {
+          throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public int getDocCount() {
+          throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean hasFreqs() {
+          throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean hasOffsets() {
+          throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean hasPositions() {
+          throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean hasPayloads() {
+          throw new UnsupportedOperationException();
+        }
+      });
+    });
+    assertThat(expected.getMessage(), containsString(value));
+  }
+
   private void addDoc(String text, RandomIndexWriter writer) throws IOException {
     Document doc = new Document();
     doc.add(newTextField("field", text, Field.Store.YES));