#845 - Fix EQL parsing to support the 'inverse' form - e.g. where 'Rob' eq firstName (where the path is on the RHS rather than LHS)

src/main/java/com/avaje/ebeaninternal/server/grammer/EqlAdapter.java

@@ -287,19 +287,38 @@ class EqlAdapter<T> extends EQLBaseListener {
     if (childCount < 3) {
       throw new IllegalStateException("expecting 3 children for comparison? " + ctx);
     }
-    String path = getLeftHandSidePath(ctx);
-    String child = child(ctx, 2);
-    if (path.equals(child)) {
-      throw new IllegalArgumentException("Invalid expression "+path+" must be on LHS of expression");
-    }
     String operator = child(ctx, 1);
     EqlOperator op = operatorMapping.get(operator);
     if (op == null) {
       throw new IllegalStateException("No operator found for " + operator);
     }
+    String path = getLeftHandSidePath(ctx);
+    String rhs = child(ctx, 2);
+    if (path.equals(rhs)) {
+      // the 'value operator path' form
+      // invert the operator and use LHS as RHS
+      op = invert(op);
+      rhs = child(ctx, 0);
+    }
 
     // RHS is Path, Literal or Named input parameter
-    helper.addExpression(path, op, child);
+    helper.addExpression(path, op, rhs);
+  }
+
+  private EqlOperator invert(EqlOperator op) {
+    switch (op) {
+      // no change
+      case EQ : return EqlOperator.EQ;
+      case IEQ : return EqlOperator.IEQ;
+      case NE : return EqlOperator.NE;
+      // invert
+      case LT : return EqlOperator.GT;
+      case LTE : return EqlOperator.GTE;
+      case GT : return EqlOperator.LT;
+      case GTE : return EqlOperator.LTE;
+      default:
+        throw new IllegalStateException("Can not invert operator "+op);
+    }
   }
 
 

src/test/java/com/avaje/ebeaninternal/server/grammer/EqlParserTest.java

@@ -30,6 +30,47 @@ public class EqlParserTest extends BaseTestCase {
     assertThat(query.getGeneratedSql()).contains("where t0.name = ?");
   }
 
+  @Test
+  public void where_eq_reverse() throws Exception {
+
+    Query<Customer> query = parse("where 'Rob' eq name");
+    query.findList();
+
+    assertThat(query.getGeneratedSql()).contains("where t0.name = ?");
+  }
+
+  @Test
+  public void where_gt_reverse() throws Exception {
+
+    Query<Customer> query = parse("where 'Rob' > name");
+    query.findList();
+    assertThat(query.getGeneratedSql()).contains("where t0.name < ?");
+  }
+
+  @Test
+  public void where_gte_reverse() throws Exception {
+
+    Query<Customer> query = parse("where 'Rob' >= name");
+    query.findList();
+    assertThat(query.getGeneratedSql()).contains("where t0.name <= ?");
+  }
+
+  @Test
+  public void where_lt_reverse() throws Exception {
+
+    Query<Customer> query = parse("where 'Rob' < name");
+    query.findList();
+    assertThat(query.getGeneratedSql()).contains("where t0.name > ?");
+  }
+
+  @Test
+  public void where_lte_reverse() throws Exception {
+
+    Query<Customer> query = parse("where 'Rob' <= name");
+    query.findList();
+    assertThat(query.getGeneratedSql()).contains("where t0.name >= ?");
+  }
+
   @Test
   public void where_ieq() throws Exception {
 
@@ -39,6 +80,14 @@ public class EqlParserTest extends BaseTestCase {
     assertThat(query.getGeneratedSql()).contains("where lower(t0.name) =?");
   }
 
+  @Test
+  public void where_ieq_reverse() throws Exception {
+
+    Query<Customer> query = parse("where 'Rob' ieq name");
+    query.findList();
+    assertThat(query.getGeneratedSql()).contains("where lower(t0.name) =?");
+  }
+
   @Test
   public void where_eq2() throws Exception {
 
@@ -58,9 +107,13 @@ public class EqlParserTest extends BaseTestCase {
     assertThat(query.getGeneratedSql()).contains("where t0.name = ?");
   }
 
-  @Test(expected = IllegalArgumentException.class)
+  @Test
   public void where_namedParam_otherOrder() {
-    parse("where :name < plannedEnd");
+    Query<Customer> query = parse("where :nm < name");
+    query.setParameter("nm", "Rob");
+    query.findList();
+
+    assertThat(query.getGeneratedSql()).contains("where t0.name > ?");
   }
 
   @Test