Adjust "||" behavior to ECMAScript

"x || y" returns the first not false value. If x is not false value,
"x || y" returns "x" itself not "true". If x is false value and y is
not false value, "x || y" returns "y" itself not "true".

If both "x" and "y" are false value, "x || y" returns "false". It is
not changed.

Before:

    null || "string value" -> true
    null || null           -> false

After:

    null || "string value" -> "string value" (changed)
    null || null           -> false          (not changed)

lib/expr.c

@@ -3155,17 +3155,28 @@ grn_expr_exec(grn_ctx *ctx, grn_obj *expr, int nargs)
         {
           grn_obj *x, *y;
           unsigned int x_boolean, y_boolean;
-          int result;
+          grn_obj *result;
           POP2ALLOC1(x, y, res);
           GRN_TRUEP(ctx, x, x_boolean);
-          GRN_TRUEP(ctx, y, y_boolean);
-          if (x_boolean || y_boolean) {
-            result = 1;
+          if (x_boolean) {
+            result = x;
           } else {
-            result = 0;
+            GRN_TRUEP(ctx, y, y_boolean);
+            if (y_boolean) {
+              result = y;
+            } else {
+              result = NULL;
+            }
+          }
+          if (result) {
+            if (res != result) {
+              grn_obj_reinit(ctx, res, result->header.domain, 0);
+              grn_obj_cast(ctx, result, res, GRN_FALSE);
+            }
+          } else {
+            grn_obj_reinit(ctx, res, GRN_DB_BOOL, 0);
+            GRN_BOOL_SET(ctx, res, GRN_FALSE);
           }
-          grn_obj_reinit(ctx, res, GRN_DB_INT32, 0);
-          GRN_INT32_SET(ctx, res, result);
         }
         code++;
         break;

test/command/suite/select/filter/logical_operation/or.expected

@@ -0,0 +1,11 @@
+table_create Users TABLE_NO_KEY
+[[0,0.0,0.0],true]
+column_create Users name COLUMN_SCALAR ShortText
+[[0,0.0,0.0],true]
+load --table Users
+[
+{"name": "Alice"}
+]
+[[0,0.0,0.0],1]
+select Users   --output_columns '_id, null || name || "unknown"'   --command_version 2
+[[0,0.0,0.0],[[[1],[["_id","UInt32"],["","null"]],[1,"Alice"]]]]

test/command/suite/select/filter/logical_operation/or.test

@@ -0,0 +1,11 @@
+table_create Users TABLE_NO_KEY
+column_create Users name COLUMN_SCALAR ShortText
+
+load --table Users
+[
+{"name": "Alice"}
+]
+
+select Users \
+  --output_columns '_id, null || name || "unknown"' \
+  --command_version 2