Don't throw exceptions in the Analyzer

Author: julian-elastic

x-pack/plugin/esql/qa/security/src/javaRestTest/java/org/elasticsearch/xpack/esql/EsqlSecurityIT.java

@@ -828,12 +828,7 @@ private void testLookupJoinFieldLevelSecurityHelper(boolean useExpressionJoin) t
         ResponseException error = expectThrows(ResponseException.class, () -> runESQLCommand("fls_user4_1", query));
         assertThat(error.getResponse().getStatusLine().getStatusCode(), equalTo(HttpStatus.SC_BAD_REQUEST));
         if (useExpressionJoin) {
-            assertThat(
-                error.getMessage(),
-                containsString(
-                    "Join condition must be between one attribute on the left side and one attribute on the right side of the join"
-                )
-            );
+            assertThat(error.getMessage(), containsString("Unsupported join filter expression:value_left == value"));
         } else {
             assertThat(error.getMessage(), containsString("Unknown column [value] in right side of join"));
         }
@@ -907,12 +902,7 @@ private void testLookupJoinFieldLevelSecurityOnAliasHelper(boolean useExpression
         ResponseException error = expectThrows(ResponseException.class, () -> runESQLCommand("fls_user4_1_alias", query));
         assertThat(error.getResponse().getStatusLine().getStatusCode(), equalTo(HttpStatus.SC_BAD_REQUEST));
         if (useExpressionJoin) {
-            assertThat(
-                error.getMessage(),
-                containsString(
-                    "Join condition must be between one attribute on the left side and one attribute on the right side of the join"
-                )
-            );
+            assertThat(error.getMessage(), containsString("Unsupported join filter expression:value_left == value"));
         } else {
             assertThat(error.getMessage(), containsString("Unknown column [value] in right side of join"));
         }

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/analysis/Analyzer.java

@@ -757,9 +757,9 @@ private Expression resolveAndOrientJoinCondition(Expression condition, Attribute
                 if (leftIsFromRight && rightIsFromLeft) {
                     return comp.swapLeftAndRight(); // Swapped orientation
                 }
-
-                // Invalid orientation (e.g., both from left or both from right)
-                throw new IllegalArgumentException(
+                return new UnresolvedAttribute(
+                    condition.source(),
+                    "unsupported",
                     "Join condition must be between one attribute on the left side and "
                         + "one attribute on the right side of the join, but found: "
                         + condition.sourceText()
@@ -800,7 +800,13 @@ private Join resolveLookupJoin(LookupJoin join) {
                             leftKeys.add(leftAttribute);
                             rightKeys.add(rightAttribute);
                         } else {
-                            throw new IllegalArgumentException("Unsupported join filter expression: " + expression);
+                            UnresolvedAttribute errorAttribute = new UnresolvedAttribute(
+                                expression.source(),
+                                "unsupported",
+                                "Unsupported join filter expression:" + expression.sourceText()
+                            );
+                            return join.withConfig(new JoinConfig(type, singletonList(errorAttribute), emptyList(), null));
+
                         }
                     }
                 } else {