chore: ignore stdin/stdout typo in COPY commands (#1976)

PostgreSQL accepts both stdin and stdout for COPY TO and COPY FROM.
The PHP PDO driver actually contains this typo, and therefore failed
when used against PGAdapter.

Fixes #1975

src/main/java/com/google/cloud/spanner/pgadapter/statements/CopyStatement.java

@@ -617,13 +617,19 @@ static ParsedCopyStatement parse(String sql) {
     }
     builder.direction = Direction.valueOf(parser.readKeyword().toUpperCase());
     if (builder.direction == Direction.FROM) {
-      if (!parser.eatKeyword("stdin")) {
+      // Silently ignore typo 'copy from stdout'.
+      // See
+      // https://github.com/postgres/postgres/blob/03ec203164119f11f0eab4c83c97a8527e2b108d/src/backend/parser/gram.y#L3463
+      if (!parser.eatKeyword("stdin") && !parser.eatKeyword("stdout")) {
         throw PGExceptionFactory.newPGException(
             "missing 'STDIN' keyword. PGAdapter only supports COPY ... FROM STDIN: " + sql,
             SQLState.SyntaxError);
       }
     } else {
-      if (!parser.eatKeyword("stdout")) {
+      // Silently ignore typo 'copy to stdin'.
+      // See
+      // https://github.com/postgres/postgres/blob/03ec203164119f11f0eab4c83c97a8527e2b108d/src/backend/parser/gram.y#L3463
+      if (!parser.eatKeyword("stdout") && !parser.eatKeyword("stdin")) {
         throw PGExceptionFactory.newPGException(
             "missing 'STDOUT' keyword. PGAdapter only supports COPY ... TO STDOUT: " + sql,
             SQLState.SyntaxError);

src/test/java/com/google/cloud/spanner/pgadapter/statements/CopyStatementTest.java

@@ -51,6 +51,14 @@ public void testParseNonCopy() {
   public void testParseDirection() {
     assertEquals(Direction.FROM, parse("copy my_table from stdin").direction);
     assertEquals(Direction.TO, parse("copy my_table to stdout").direction);
+
+    // PostgreSQL accepts this kind of typo.
+    // See
+    // https://github.com/postgres/postgres/blob/03ec203164119f11f0eab4c83c97a8527e2b108d/src/backend/parser/gram.y#L3463
+    assertEquals(Direction.FROM, parse("copy my_table from stdout").direction);
+    assertEquals(Direction.TO, parse("copy my_table to stdin").direction);
+
+    // COPY BOTH is not supported.
     assertThrows(PGException.class, () -> parse("copy my_table both stdin"));
   }