Update notes.md

docs/notes.md

@@ -1,6 +1,69 @@
 Additional Notes
 ================
 
+Variadic Arguments
+------------------
+
+When mocking methods with variadic arguments, some complexities are introduced. Before this PR: https://github.com/vektra/mockery/pull/123, mocking a variadic method looked like this:
+
+```go
+type Foo interface {
+  Bar(s ...string) error
+}
+
+func TestFoo(t *testing.T) {
+  m := NewMockFoo(t)
+  m.On("Bar", []string{"hello", "world"}).Return(nil)
+}
+```
+
+After the PR, you could use this syntax:
+
+```go
+func TestFoo(t *testing.T) {
+  m := NewMockFoo(t)
+  m.On("Bar", "hello", "world").Return(nil)
+```
+
+This introduces ambiguities because if you want to do something like this:
+
+```
+m.On("Bar", mock.Anything).Return(nil)
+```
+
+This is impossible to distinguish between these two intentions:
+1. Any number of variadic arguments of any value
+2. A single variadic argument of any value
+
+This is fixed in https://github.com/vektra/mockery/pull/359 where you can provide `unroll-variadic: False` to get back to the old behavior. Thus, if you want to assert the first case, you can then do:
+
+```
+m.On("Bar", mock.Anything).Return(nil)
+```
+
+If you want to specify the second case, you must set `unroll-variadic: True`. Then this assertion's intention will be modified to mean the second case:
+
+```
+m.On("Bar", mock.Anything).Return(nil)
+```
+
+An upstream patch to `testify` is currently underway to allow passing `mock.Anything` directly to the variadic slice: https://github.com/stretchr/testify/pull/1348
+
+If this is merged, it would become possible to describe the above two cases respectively:
+
+```go
+// case 1
+m.On("Bar", mock.Anything).Return(nil)
+// case 2
+m.On("Bar", []interface{}{mock.Anything}).Return(nil)
+```
+
+References:
+- https://github.com/vektra/mockery/pull/359
+- https://github.com/vektra/mockery/pull/123
+- https://github.com/vektra/mockery/pull/550
+- https://github.com/vektra/mockery/issues/541
+
 Semantic Versioning
 -------------------
 
@@ -19,4 +82,4 @@ Mocking interfaces in `main`
 ----------------------------
 
 When your interfaces are in the main package, you should supply the `--inpackage` flag.
-This will generate mocks in the same package as the target code, avoiding import issues.
+This will generate mocks in the same package as the target code, avoiding import issues.