Don't append display name suffix to data table file keys (#7104)

`CsvDataTableStore.fileKey()` always appended a sanitized suffix derived
from `getInstanceName()`, which defaults to the display name. This meant
every data table got a suffix like `--recipe-performance-c5de` even when
no custom instance name was set and no disambiguation was needed.

Now, when no group is set, a suffix is only added when the instance name
was explicitly customized via `withInstanceName()` (i.e. differs from
the default display name). Plain data tables like `RecipeRunStats` get a
clean key: `org.openrewrite.table.RecipeRunStats`.

Author: jkschneider

rewrite-core/src/main/java/org/openrewrite/CsvDataTableStore.java

@@ -242,11 +242,19 @@ void close() {
      */
     public static String fileKey(DataTable<?> dataTable) {
         String group = dataTable.getGroup();
-        String suffix = group != null ? group : dataTable.getInstanceName();
-        if (suffix.equals(dataTable.getName())) {
+        if (group != null) {
+            if (group.equals(dataTable.getName())) {
+                return dataTable.getName();
+            }
+            return dataTable.getName() + "--" + sanitize(group);
+        }
+        // Only add a suffix when the instance name was explicitly customized
+        // (i.e. differs from the default display name)
+        String instanceName = dataTable.getInstanceName();
+        if (instanceName.equals(dataTable.getDisplayName())) {
             return dataTable.getName();
         }
-        return dataTable.getName() + "--" + sanitize(suffix);
+        return dataTable.getName() + "--" + sanitize(instanceName);
     }
 
     /**

rewrite-core/src/test/java/org/openrewrite/DataTableStoreTest.java

@@ -246,6 +246,31 @@ void csvStoreReadDescriptor(@TempDir Path tempDir) throws Exception {
         }
     }
 
+    // =========================================================================
+    // CsvDataTableStore.fileKey
+    // =========================================================================
+
+    @Test
+    void fileKeyNoSuffixWhenInstanceNameNotCustomized() {
+        TestTable table = new TestTable(Recipe.noop());
+        assertThat(CsvDataTableStore.fileKey(table)).isEqualTo(TestTable.class.getName());
+    }
+
+    @Test
+    void fileKeySuffixWhenInstanceNameCustomized() {
+        TestTable table = new TestTable(Recipe.noop())
+                .withInstanceName(() -> "custom instance");
+        String key = CsvDataTableStore.fileKey(table);
+        assertThat(key).startsWith(TestTable.class.getName() + "--");
+    }
+
+    @Test
+    void fileKeySuffixFromGroup() {
+        TestTable table = new TestTable(Recipe.noop()).withGroup("my-group");
+        String key = CsvDataTableStore.fileKey(table);
+        assertThat(key).startsWith(TestTable.class.getName() + "--");
+    }
+
     // =========================================================================
     // CsvDataTableStore.sanitize
     // =========================================================================