Fixed diffing thinking orphaned keys were real

config/file.go

@@ -147,8 +147,12 @@ func ParseValue (str string) (Value, error) {
 // ErrMalformedKey.
 func (this *File) Has (key string) (bool, error) {
 	if !KeyValid(key) { return false, ErrMalformedKey }
-	_, ok := this.keys[key]
-	return ok, nil
+	if index, ok := this.keys[key]; ok {
+		if _, ok := this.lines[index].(entry); ok {
+			return true, nil
+		}
+	}
+	return false, nil
 }
 
 // Get gets the keyed value. If the value is unspecified, it returns nil,
@@ -214,19 +218,31 @@ func (this *File) Diff (other *File) map[string] struct { } {
 	// - keys only we have
 	// - keys we both have, but are different
 	for key, index := range this.keys {
+		thisEntry, ok := this.lines[index].(entry)
+		if !ok { continue }
+	
 		otherIndex, ok := other.keys[key]
 		if !ok {
 			diff[key] = struct { } { }
 			continue
 		}
-		if !this.lines[index].(entry).value.Equals(other.lines[otherIndex].(entry).value) {
+		otherEntry, ok := other.lines[otherIndex].(entry)
+		if !ok {
+			diff[key] = struct { } { }
+			continue
+		}
+		
+		if !thisEntry.value.Equals(otherEntry.value) {
 			diff[key] = struct { } { }
 		}
 	}
 
 	// - keys only they have
 	for key := range other.keys {
-		if _, has := this.keys[key]; !has {
+		if otherHas, _ := other.Has(key); !otherHas {
+			continue
+		}
+		if thisHas, _ := this.Has(key); !thisHas {
 			diff[key] = struct { } { }
 		}
 	}

config/file_test.go

@@ -123,6 +123,36 @@ yetAnotherThing = 0.23498
 	}
 }
 
+func TestDiffReset (test *testing.T) {
+	file1 := parseFileString(test,
+`key4=0
+key1=value1
+keyToDelete=true
+# comment
+key2=34`)
+	file2 := parseFileString(test,
+`key1=value2
+key2=34
+anotherKeyToDelete=false
+# comment
+
+key3=0.2`)
+	file1.Reset("keyToDelete")
+	file2.Reset("anotherKeyToDelete")
+	diff := file1.Diff(file2)
+	correct := map[string] struct { } {
+		"key1": struct { } { },
+		"key3": struct { } { },
+		"key4": struct { } { },
+	}
+	if !maps.Equal(diff, correct) {
+		test.Error("diffs do not match")
+		test.Errorf("EXPECTED:\n%v", correct)
+		test.Errorf("GOT:\n%v", diff)
+		test.Fail()
+	}
+}
+
 func TestDiff (test *testing.T) {
 	file1 := parseFileString(test,
 `key4=0