From a7fe47ddb539b6c7698ea85afba756f7a8f7e71e Mon Sep 17 00:00:00 2001
From: David Nichols <david.nichols@qoretechnologies.com>
Date: Sun, 2 Feb 2020 10:45:49 +0100
Subject: [PATCH] refs #3545 updated Mapper to accept the null input provider

---
 qlib/Mapper.qm | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/qlib/Mapper.qm b/qlib/Mapper.qm
index 827e48203c..662de3911e 100644
--- a/qlib/Mapper.qm
+++ b/qlib/Mapper.qm
@@ -871,7 +871,7 @@ Mapper mapv(DataMap);
                 "API", opts.input_provider.getName(), self.className());
         }
 
-        if (!input) {
+        if (!exists input) {
             error("\"input_provider\" %y passed to %s::constructor() has an empty record type",
                 input_provider.getName(), self.className());
         }
@@ -888,10 +888,10 @@ Mapper mapv(DataMap);
 
     private:internal *hash<string, AbstractDataField> getFields(string pfx, AbstractDataProviderType type) {
         *hash<string, AbstractDataField> fields = type.getFields();
-        if (!fields) {
+        if (!fields && pfx != "input") {
             error("%s provider provides type %y which cannot be mapped", pfx, type.getName());
         }
-        return fields;
+        return fields ?? {};
     }
 
     private setOutputProvider(hash<auto> opts) {