core: Tests for hasComputedSubKeys fix

This covers:

 * Complex sets with computed fields in a set
 * Complex lists with computed fields in a set

Adding a test to test basic lists with computed fields seemed to fail,
but possibly for an unrelated reason (the list returned as nil). The fix
to this inparticular case may be out of the scope of this specific
issue.

Reference gist and details in hashicorp#9171.

helper/schema/schema_test.go

@@ -3267,6 +3267,157 @@ func TestSchemaMap_DiffSuppress(t *testing.T) {
 
 			Err: false,
 		},
+
+		"Complex structure with set of computed string should mark root set as computed": {
+			Schema: map[string]*Schema{
+				"outer": &Schema{
+					Type:     TypeSet,
+					Optional: true,
+					Elem: &Resource{
+						Schema: map[string]*Schema{
+							"outer_str": &Schema{
+								Type:     TypeString,
+								Optional: true,
+							},
+							"inner": &Schema{
+								Type:     TypeSet,
+								Optional: true,
+								Elem: &Resource{
+									Schema: map[string]*Schema{
+										"inner_str": &Schema{
+											Type:     TypeString,
+											Optional: true,
+										},
+									},
+								},
+								Set: func(v interface{}) int {
+									return 2
+								},
+							},
+						},
+					},
+					Set: func(v interface{}) int {
+						return 1
+					},
+				},
+			},
+
+			State: nil,
+
+			Config: map[string]interface{}{
+				"outer": []map[string]interface{}{
+					map[string]interface{}{
+						"outer_str": "foo",
+						"inner": []map[string]interface{}{
+							map[string]interface{}{
+								"inner_str": "${var.bar}",
+							},
+						},
+					},
+				},
+			},
+
+			ConfigVariables: map[string]ast.Variable{
+				"var.bar": interfaceToVariableSwallowError(config.UnknownVariableValue),
+			},
+
+			Diff: &terraform.InstanceDiff{
+				Attributes: map[string]*terraform.ResourceAttrDiff{
+					"outer.#": &terraform.ResourceAttrDiff{
+						Old: "0",
+						New: "1",
+					},
+					"outer.~1.outer_str": &terraform.ResourceAttrDiff{
+						Old: "",
+						New: "foo",
+					},
+					"outer.~1.inner.#": &terraform.ResourceAttrDiff{
+						Old: "0",
+						New: "1",
+					},
+					"outer.~1.inner.~2.inner_str": &terraform.ResourceAttrDiff{
+						Old: "",
+						New: "${var.bar}",
+					},
+				},
+			},
+
+			Err: false,
+		},
+
+		"Complex structure with complex list of computed string should mark root set as computed": {
+			Schema: map[string]*Schema{
+				"outer": &Schema{
+					Type:     TypeSet,
+					Optional: true,
+					Elem: &Resource{
+						Schema: map[string]*Schema{
+							"outer_str": &Schema{
+								Type:     TypeString,
+								Optional: true,
+							},
+							"inner": &Schema{
+								Type:     TypeList,
+								Optional: true,
+								Elem: &Resource{
+									Schema: map[string]*Schema{
+										"inner_str": &Schema{
+											Type:     TypeString,
+											Optional: true,
+										},
+									},
+								},
+							},
+						},
+					},
+					Set: func(v interface{}) int {
+						return 1
+					},
+				},
+			},
+
+			State: nil,
+
+			Config: map[string]interface{}{
+				"outer": []map[string]interface{}{
+					map[string]interface{}{
+						"outer_str": "foo",
+						"inner": []map[string]interface{}{
+							map[string]interface{}{
+								"inner_str": "${var.bar}",
+							},
+						},
+					},
+				},
+			},
+
+			ConfigVariables: map[string]ast.Variable{
+				"var.bar": interfaceToVariableSwallowError(config.UnknownVariableValue),
+			},
+
+			Diff: &terraform.InstanceDiff{
+				Attributes: map[string]*terraform.ResourceAttrDiff{
+					"outer.#": &terraform.ResourceAttrDiff{
+						Old: "0",
+						New: "1",
+					},
+					"outer.~1.outer_str": &terraform.ResourceAttrDiff{
+						Old: "",
+						New: "foo",
+					},
+					"outer.~1.inner.#": &terraform.ResourceAttrDiff{
+						Old: "0",
+						New: "1",
+					},
+					"outer.~1.inner.0.inner_str": &terraform.ResourceAttrDiff{
+						Old: "",
+						New: "${var.bar}",
+					},
+				},
+			},
+
+			Err: false,
+		},
 	}
 
 	for tn, tc := range cases {