Add test to check return values of frequency and norm when there are no frequencies

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene90/TestLucene90PostingsFormat.java

@@ -52,6 +52,11 @@ protected Codec getCodec() {
     return codec;
   }
 
+  @Override
+  protected boolean indexFakeImpacts() {
+    return true;
+  }
+
   /** Make sure the final sub-block(s) are not skipped. */
   public void testFinalBlock() throws Exception {
     Directory d = newDirectory();

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene912/TestLucene912PostingsFormat.java

@@ -49,6 +49,11 @@ protected Codec getCodec() {
     return TestUtil.alwaysPostingsFormat(new Lucene912RWPostingsFormat());
   }
 
+  @Override
+  protected boolean indexFakeImpacts() {
+    return true;
+  }
+
   public void testVInt15() throws IOException {
     byte[] bytes = new byte[5];
     ByteArrayDataOutput out = new ByteArrayDataOutput(bytes);

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene99/TestLucene99PostingsFormat.java

@@ -53,6 +53,11 @@ protected Codec getCodec() {
     return codec;
   }
 
+  @Override
+  protected boolean indexFakeImpacts() {
+    return true;
+  }
+
   /** Make sure the final sub-block(s) are not skipped. */
   public void testFinalBlock() throws Exception {
     Directory d = newDirectory();

lucene/codecs/src/test/org/apache/lucene/codecs/memory/TestDirectPostingsFormat.java

@@ -34,4 +34,9 @@ protected boolean isPostingsEnumReuseImplemented() {
   protected Codec getCodec() {
     return codec;
   }
+
+  @Override
+  protected boolean indexFakeImpacts() {
+    return true;
+  }
 }

lucene/core/src/test/org/apache/lucene/codecs/perfield/TestPerFieldPostingsFormat.java

@@ -39,4 +39,10 @@ public void testMergeStability() throws Exception {
   public void testPostingsEnumReuse() throws Exception {
     assumeTrue("The MockRandom PF randomizes content on the fly, so we can't check it", false);
   }
+
+  @Override
+  protected boolean indexFakeImpacts() {
+    // we don't know if the codec will use fake impls or not, true is the safe value
+    return true;
+  }
 }

lucene/test-framework/src/java/org/apache/lucene/tests/index/BasePostingsFormatTestCase.java

@@ -45,6 +45,8 @@
 import org.apache.lucene.index.CodecReader;
 import org.apache.lucene.index.DirectoryReader;
 import org.apache.lucene.index.Fields;
+import org.apache.lucene.index.FreqAndNormBuffer;
+import org.apache.lucene.index.ImpactsEnum;
 import org.apache.lucene.index.IndexOptions;
 import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.IndexWriter;
@@ -1798,4 +1800,31 @@ public void testDocIDRunEnd() throws Exception {
     }
     dir.close();
   }
+
+  protected boolean indexFakeImpacts() {
+    return false;
+  }
+
+  public void testImpactsNoFreqs() throws Exception {
+    assumeFalse("We index fake impacts between 9.0 in 9.12", indexFakeImpacts());
+    try (Directory dir = newDirectory()) {
+      IndexWriterConfig iwc = newIndexWriterConfig(new MockAnalyzer(random()));
+      iwc.setCodec(getCodec());
+      try (RandomIndexWriter iw = new RandomIndexWriter(random(), dir, iwc)) {
+        Document doc = new Document();
+        doc.add(newStringField("field", "value", Field.Store.NO));
+        iw.addDocument(doc);
+        try (DirectoryReader ir = iw.getReader()) {
+          LeafReader ar = getOnlyLeafReader(ir);
+          TermsEnum termsEnum = ar.terms("field").iterator();
+          termsEnum.seekExact(new BytesRef("value"));
+          ImpactsEnum impactsEnum = termsEnum.impacts(FREQS);
+          FreqAndNormBuffer freqAndNormBuffer = impactsEnum.getImpacts().getImpacts(0);
+          assertEquals(1, freqAndNormBuffer.size);
+          assertEquals(1, freqAndNormBuffer.freqs[0]);
+          assertEquals(1L, freqAndNormBuffer.norms[0]);
+        }
+      }
+    }
+  }
 }

lucene/test-framework/src/test/org/apache/lucene/tests/codecs/asserting/TestAssertingPostingsFormat.java

@@ -32,4 +32,9 @@ protected Codec getCodec() {
   protected boolean isPostingsEnumReuseImplemented() {
     return false;
   }
+
+  @Override
+  protected boolean indexFakeImpacts() {
+    return true;
+  }
 }