fix: correct the type matcher to treat JsonNull as a null #981

Author: Ronald Holshausen

core/matchers/src/main/kotlin/au/com/dius/pact/core/matchers/MatcherExecutor.kt

@@ -130,7 +130,7 @@ fun <M : Mismatch> matchEquality(
   mismatchFactory: MismatchFactory<M>
 ): List<M> {
   val matches = when {
-    actual == null && expected == null -> true
+    (actual == null || actual is JsonNull) && (expected == null || expected is JsonNull) -> true
     actual is Element && expected is Element -> actual.tagName == expected.tagName
     else -> actual != null && actual == expected
   }
@@ -184,8 +184,8 @@ fun <M : Mismatch> matchType(
       (expected.isNumber && actual.isNumber) ||
       (expected.isString && actual.isString))) {
       emptyList()
-  } else if (expected == null) {
-    if (actual == null) {
+  } else if (expected == null || expected is JsonNull) {
+    if (actual == null || actual is JsonNull) {
       emptyList()
     } else {
       listOf(mismatchFactory.create(expected, actual, "Expected ${valueOf(actual)} to be null", path))

core/matchers/src/test/groovy/au/com/dius/pact/core/matchers/MatcherExecutorSpec.groovy

@@ -11,6 +11,7 @@ import au.com.dius.pact.core.model.matchingrules.RegexMatcher
 import au.com.dius.pact.core.model.matchingrules.TimeMatcher
 import au.com.dius.pact.core.model.matchingrules.TimestampMatcher
 import au.com.dius.pact.core.model.matchingrules.TypeMatcher
+import com.google.gson.JsonNull
 import spock.lang.Specification
 import spock.lang.Unroll
 
@@ -35,13 +36,16 @@ class MatcherExecutorSpec extends Specification {
     MatcherExecutorKt.domatch(EqualsMatcher.INSTANCE, path, expected, actual, mismatchFactory).empty == mustBeEmpty
 
     where:
-    expected | actual || mustBeEmpty
-    '100'    | '100'  || true
-    100      | '100'  || false
-    100      | 100    || true
-    null     | null   || true
-    '100'    | null   || false
-    null     | 100    || false
+    expected          | actual            || mustBeEmpty
+    '100'             | '100'             || true
+    100               | '100'             || false
+    100               | 100               || true
+    null              | null              || true
+    '100'             | null              || false
+    null              | 100               || false
+    JsonNull.INSTANCE | null              || true
+    null              | JsonNull.INSTANCE || true
+    JsonNull.INSTANCE | JsonNull.INSTANCE || true
   }
 
   @Unroll
@@ -62,15 +66,18 @@ class MatcherExecutorSpec extends Specification {
     MatcherExecutorKt.domatch(TypeMatcher.INSTANCE, path, expected, actual, mismatchFactory).empty == mustBeEmpty
 
     where:
-    expected        | actual                     || mustBeEmpty
-    'Harry'         | 'Some other string'        || true
-    100             | 200.3                      || true
-    true            | false                      || true
-    null            | null                       || true
-    '200'           | 200                        || false
-    200             | null                       || false
-    [100, 200, 300] | [200.3]                    || true
-    [a: 100]        | [a: 200.3, b: 200, c: 300] || true
+    expected          | actual                     || mustBeEmpty
+    'Harry'           | 'Some other string'        || true
+    100               | 200.3                      || true
+    true              | false                      || true
+    null              | null                       || true
+    '200'             | 200                        || false
+    200               | null                       || false
+    [100, 200, 300]   | [200.3]                    || true
+    [a: 100]          | [a: 200.3, b: 200, c: 300] || true
+    JsonNull.INSTANCE | null                       || true
+    null              | JsonNull.INSTANCE          || true
+    JsonNull.INSTANCE | JsonNull.INSTANCE          || true
   }
 
   @Unroll