commit 1ff37a00977edb348bb7281443f4115190ab7086
author Mihai Budiu <mbudiu@feldera.com> Fri Apr 25 17:13:47 2025 -0700
committer Mihai Budiu <mbudiu@feldera.com> Tue Apr 29 15:12:47 2025 -0700
tree 660576f0e7b4dcd602c2d1dfdb98ac7f9398f7cd
parent f438bf62e075b830fa1bd1f1aa28358123ffbe4a

[CALCITE-6986] Parser rejects SQL sources that produce an empty statement list

Signed-off-by: Mihai Budiu <mbudiu@feldera.com>

core/src/main/codegen/templates/Parser.jj

diff --git a/core/src/main/codegen/templates/Parser.jj b/core/src/main/codegen/templates/Parser.jj
index c02de6c..fa7593c 100644
--- a/core/src/main/codegen/templates/Parser.jj
+++ b/core/src/main/codegen/templates/Parser.jj
@@ -1115,17 +1115,19 @@
     SqlNode stmt;
 }
 {
-    stmt = SqlStmt() {
-        stmtList.add(stmt);
-    }
     (
-        <SEMICOLON>
-        [
-            stmt = SqlStmt() {
-                stmtList.add(stmt);
-            }
-        ]
-    )*
+        stmt = SqlStmt() {
+            stmtList.add(stmt);
+        }
+        (
+            <SEMICOLON>
+            [
+                stmt = SqlStmt() {
+                    stmtList.add(stmt);
+                }
+            ]
+        )*
+    )?
     <EOF>
     {
         return new SqlNodeList(stmtList, Span.of(stmtList).pos());

core/src/main/java/org/apache/calcite/sql/parser/SqlParserPos.java

diff --git a/core/src/main/java/org/apache/calcite/sql/parser/SqlParserPos.java b/core/src/main/java/org/apache/calcite/sql/parser/SqlParserPos.java
index 53e6234..97fb72c 100644
--- a/core/src/main/java/org/apache/calcite/sql/parser/SqlParserPos.java
+++ b/core/src/main/java/org/apache/calcite/sql/parser/SqlParserPos.java
@@ -229,7 +229,7 @@ public static SqlParserPos sum(Iterable<SqlParserPos> poses) {
             ? (List<SqlParserPos>) poses
             : Lists.newArrayList(poses);
     if (list.isEmpty()) {
-      throw new AssertionError();
+      return SqlParserPos.ZERO;
     }
     final SqlParserPos pos0 = list.get(0);
     if (list.size() == 1) {

testkit/src/main/java/org/apache/calcite/sql/parser/SqlParserTest.java

diff --git a/testkit/src/main/java/org/apache/calcite/sql/parser/SqlParserTest.java b/testkit/src/main/java/org/apache/calcite/sql/parser/SqlParserTest.java
index a01a8c7..0939a59 100644
--- a/testkit/src/main/java/org/apache/calcite/sql/parser/SqlParserTest.java
+++ b/testkit/src/main/java/org/apache/calcite/sql/parser/SqlParserTest.java
@@ -2111,6 +2111,14 @@ void checkPeriodPredicate(Checker checker) {
             + "FROM `DEPT`))) AND (3 = 4))");
   }
 
+  /** Test case for <a href="https://issues.apache.org/jira/browse/CALCITE-6986">[CALCITE-6986]
+   * Parser rejects SQL sources that produce an empty statement list</a>. */
+  @Test public void testEmpty() {
+    sql("").list().ok();
+    sql(" ").list().ok();
+    sql("-- comment").list().ok();
+  }
+
   @Test void testUnique() {
     sql("select * from dept where unique (select 1 from emp where emp.deptno = dept.deptno)")
         .ok("SELECT *\n"

testkit/src/main/java/org/apache/calcite/sql/test/SqlTestFactory.java

diff --git a/testkit/src/main/java/org/apache/calcite/sql/test/SqlTestFactory.java b/testkit/src/main/java/org/apache/calcite/sql/test/SqlTestFactory.java
index 86476b5..9ecc842 100644
--- a/testkit/src/main/java/org/apache/calcite/sql/test/SqlTestFactory.java
+++ b/testkit/src/main/java/org/apache/calcite/sql/test/SqlTestFactory.java
@@ -130,6 +130,12 @@ protected SqlTestFactory(CatalogReaderFactory catalogReaderFactory,
 
   /** Creates a parser. */
   public SqlParser createParser(String sql) {
+    if (sql.isEmpty()) {
+      // I could not figure out how to convince the grammar to accept an empty
+      // string.  Without this change I get an exception in the token reader in code
+      // generated by JavaCC
+      sql = " ";
+    }
     SqlParser.Config parserConfig = parserConfig();
     return SqlParser.create(new SourceStringReader(sql), parserConfig);
   }