feat: map nil properties to null instead of undefined

DynamicMapper · Oct 19, 2019 · 57ae23d · 57ae23d
1 parent a07748f
commit 57ae23d
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Showing 6 changed files with 49 additions and 21 deletions.
diff --git a/src/configuration/member-configuration-expression.ts b/src/configuration/member-configuration-expression.ts
@@ -49,7 +49,7 @@ export class MemberConfigurationExpression<TSource, TDestination, TMember>
         this.propertyMapActions.push(pm => pm.precondition = condition);
     }
 
-    nullSubstitute(nullSubstitute: ((src: TSource) => TMember) | TMember | null): void {
+    nullSubstitute(nullSubstitute: ((src: TSource) => TMember) | TMember): void {
         this.propertyMapActions.push(pm => pm.nullSubstitute = nullSubstitute);
     }
 

diff --git a/src/execution/type-map-plan-builder.ts b/src/execution/type-map-plan-builder.ts
@@ -160,24 +160,19 @@ export class TypeMapPlanBuilder {
             throw new Error(`Unable to detect source member for destination member "${memberMap.destinationMember.toString()}"`);
         }
 
-        if (typeof memberMap.nullSubstitute !== 'undefined') {
-            const prevResolver = resolver;
-            resolver = (source: any, destination: any, context: ResolutionContext) => {
-                const value = prevResolver(source, destination, context);
-
-                if (value == null) {
-                    if (typeof memberMap.nullSubstitute === 'function') {
-                        return memberMap.nullSubstitute(source);
-                    }
+        return (source: any, destination: any, context: ResolutionContext) => {
+            const value = resolver(source, destination, context);
 
-                    return memberMap.nullSubstitute;
+            if (value == null && typeof memberMap.nullSubstitute !== 'undefined') {
+                if (typeof memberMap.nullSubstitute === 'function') {
+                    return memberMap.nullSubstitute(source);
                 }
 
-                return value;
-            };
-        }
+                return memberMap.nullSubstitute;
+            }
 
-        return resolver;
+            return value == null ? null : value;
+        };
     }
 
     private getIgnoredSourceMembers(): ReadonlyArray<MemberInfo> {

diff --git a/src/interface.ts b/src/interface.ts
@@ -85,7 +85,7 @@ export interface IMemberMap {
     valueTransformers: ReadonlyArray<ValueTransformer<any>>;
     sourceMembers: ReadonlyArray<MemberInfo>;
     destinationMember: MemberInfo;
-    nullSubstitute: any | null;
+    nullSubstitute: any;
     pair: MappingPair<any, any> | undefined;
 }
 
@@ -154,7 +154,7 @@ export interface IMemberConfigurationExpression<TSource, TDestination, TMember>
     /**
      * Substitute a custom value when the source member resolves as null or undefined.
      */
-    nullSubstitute(nullSubstitute: ((src: TSource) => TMember) | TMember | null): void;
+    nullSubstitute(nullSubstitute: ((src: TSource) => TMember) | TMember): void;
 
     /**
      * Ignore this member during mapping.

diff --git a/src/property-map.ts b/src/property-map.ts
@@ -10,7 +10,7 @@ export class PropertyMap implements IMemberMap {
 
     public customMappingFunction: MappingFunction;
 
-    public nullSubstitute: any | null;
+    public nullSubstitute: any;
 
     public ignored: boolean;
 

diff --git a/test/general.spec.ts b/test/general.spec.ts
@@ -50,4 +50,37 @@ describe('General mapping', () => {
             expect(destination[1].someValue).toBe('bar');
         });
     });
+
+    describe('when mapping nil properties', () => {
+        class ModelObject {
+            value: string | null;
+        }
+
+        class ModelDto {
+            value: string | null;
+        }
+
+        const pair = new MappingPair(ModelObject, ModelDto);
+
+        const mapper = new MapperConfiguration(cfg => {
+            cfg.createMap(pair, {
+                value: opt => opt.auto()
+            });
+        }).createMapper();
+
+        it('should map to null', () => {
+            const source = new ModelObject();
+
+            expect(mapper.map(pair, source)).toEqual({
+                value: null
+            });
+
+            source.value = null;
+
+            expect(mapper.map(pair, source)).toEqual({
+                value: null
+            });
+        });
+    });
+
 });
diff --git a/test/strict-map-all-member-config.spec.ts b/test/strict-map-all-member-config.spec.ts
@@ -21,14 +21,14 @@ describe('Strict map with all member config', () => {
                 opt.auto();
                 opt.nullSubstitute(123);
             }
-        }, opt => opt.nullSubstitute(null));
+        }, opt => opt.nullSubstitute('empty'));
     }).createMapper();
 
-    it('should substitute all nil members to null', () => {
+    it('should substitute all nil members to custom value', () => {
         const destination = mapper.map(pair, new Source());
 
         expect(destination).toEqual({
-            another: null,
+            another: 'empty',
             other: 123
         });
     });