Merge pull request #1019 from hashicorp/f-state-equality

terraform: State.Equal to check for state equality

terraform/state.go

@@ -134,6 +134,30 @@ func (s *State) RootModule() *ModuleState {
 	return root
 }
 
+// Equal tests if one state is equal to another.
+func (s *State) Equal(other *State) bool {
+	// If the versions are different, they're certainly not equal
+	if s.Version != other.Version {
+		return false
+	}
+
+	// If any of the modules are not equal, then this state isn't equal
+	for _, m := range s.Modules {
+		// This isn't very optimal currently but works.
+		otherM := other.ModuleByPath(m.Path)
+		if otherM == nil {
+			return false
+		}
+
+		// If they're not equal, then we're not equal!
+		if !m.Equal(otherM) {
+			return false
+		}
+	}
+
+	return true
+}
+
 func (s *State) init() {
 	if s.Version == 0 {
 		s.Version = StateVersion
@@ -289,6 +313,54 @@ type ModuleState struct {
 	Dependencies []string `json:"depends_on,omitempty"`
 }
 
+// Equal tests whether one module state is equal to another.
+func (m *ModuleState) Equal(other *ModuleState) bool {
+	// Paths must be equal
+	if !reflect.DeepEqual(m.Path, other.Path) {
+		return false
+	}
+
+	// Outputs must be equal
+	if len(m.Outputs) != len(other.Outputs) {
+		return false
+	}
+	for k, v := range m.Outputs {
+		if other.Outputs[k] != v {
+			return false
+		}
+	}
+
+	// Dependencies must be equal. This sorts these in place but
+	// this shouldn't cause any problems.
+	sort.Strings(m.Dependencies)
+	sort.Strings(other.Dependencies)
+	if len(m.Dependencies) != len(other.Dependencies) {
+		return false
+	}
+	for i, d := range m.Dependencies {
+		if other.Dependencies[i] != d {
+			return false
+		}
+	}
+
+	// Resources must be equal
+	if len(m.Resources) != len(other.Resources) {
+		return false
+	}
+	for k, r := range m.Resources {
+		otherR, ok := other.Resources[k]
+		if !ok {
+			return false
+		}
+
+		if !r.Equal(otherR) {
+			return false
+		}
+	}
+
+	return true
+}
+
 // IsRoot says whether or not this module diff is for the root module.
 func (m *ModuleState) IsRoot() bool {
 	return reflect.DeepEqual(m.Path, rootModulePath)
@@ -522,6 +594,63 @@ type ResourceState struct {
 	Tainted []*InstanceState `json:"tainted,omitempty"`
 }
 
+// Equal tests whether two ResourceStates are equal.
+func (s *ResourceState) Equal(other *ResourceState) bool {
+	if s.Type != other.Type {
+		return false
+	}
+
+	// Dependencies must be equal
+	sort.Strings(s.Dependencies)
+	sort.Strings(other.Dependencies)
+	if len(s.Dependencies) != len(other.Dependencies) {
+		return false
+	}
+	for i, d := range s.Dependencies {
+		if other.Dependencies[i] != d {
+			return false
+		}
+	}
+
+	// States must be equal
+	if !s.Primary.Equal(other.Primary) {
+		return false
+	}
+
+	// Tainted
+	taints := make(map[string]*InstanceState)
+	for _, t := range other.Tainted {
+		if t == nil {
+			continue
+		}
+
+		taints[t.ID] = t
+	}
+	for _, t := range s.Tainted {
+		if t == nil {
+			continue
+		}
+
+		otherT, ok := taints[t.ID]
+		if !ok {
+			return false
+		}
+		delete(taints, t.ID)
+
+		if !t.Equal(otherT) {
+			return false
+		}
+	}
+
+	// This means that we have stuff in other tainted that we don't
+	// have, so it is not equal.
+	if len(taints) > 0 {
+		return false
+	}
+
+	return true
+}
+
 func (r *ResourceState) init() {
 	if r.Primary == nil {
 		r.Primary = &InstanceState{}
@@ -618,6 +747,35 @@ func (i *InstanceState) deepcopy() *InstanceState {
 	return n
 }
 
+func (s *InstanceState) Equal(other *InstanceState) bool {
+	// Short circuit some nil checks
+	if s == nil || other == nil {
+		return s == other
+	}
+
+	// IDs must be equal
+	if s.ID != other.ID {
+		return false
+	}
+
+	// Attributes must be equal
+	if len(s.Attributes) != len(other.Attributes) {
+		return false
+	}
+	for k, v := range s.Attributes {
+		otherV, ok := other.Attributes[k]
+		if !ok {
+			return false
+		}
+
+		if v != otherV {
+			return false
+		}
+	}
+
+	return true
+}
+
 // MergeDiff takes a ResourceDiff and merges the attributes into
 // this resource state in order to generate a new state. This new
 // state can be used to provide updated attribute lookups for

terraform/state_test.go

@@ -111,6 +111,207 @@ func TestStateModuleOrphans_nilConfig(t *testing.T) {
 	}
 }
 
+func TestStateEqual(t *testing.T) {
+	cases := []struct {
+		Result   bool
+		One, Two *State
+	}{
+		// Different versions
+		{
+			false,
+			&State{Version: 5},
+			&State{Version: 2},
+		},
+
+		// Different modules
+		{
+			false,
+			&State{
+				Modules: []*ModuleState{
+					&ModuleState{
+						Path: RootModulePath,
+					},
+				},
+			},
+			&State{},
+		},
+
+		{
+			true,
+			&State{
+				Modules: []*ModuleState{
+					&ModuleState{
+						Path: RootModulePath,
+					},
+				},
+			},
+			&State{
+				Modules: []*ModuleState{
+					&ModuleState{
+						Path: RootModulePath,
+					},
+				},
+			},
+		},
+	}
+
+	for i, tc := range cases {
+		if tc.One.Equal(tc.Two) != tc.Result {
+			t.Fatalf("Bad: %d\n\n%s\n\n%s", i, tc.One.String(), tc.Two.String())
+		}
+	}
+}
+
+func TestResourceStateEqual(t *testing.T) {
+	cases := []struct {
+		Result   bool
+		One, Two *ResourceState
+	}{
+		// Different types
+		{
+			false,
+			&ResourceState{Type: "foo"},
+			&ResourceState{Type: "bar"},
+		},
+
+		// Different dependencies
+		{
+			false,
+			&ResourceState{Dependencies: []string{"foo"}},
+			&ResourceState{Dependencies: []string{"bar"}},
+		},
+
+		{
+			false,
+			&ResourceState{Dependencies: []string{"foo", "bar"}},
+			&ResourceState{Dependencies: []string{"foo"}},
+		},
+
+		{
+			true,
+			&ResourceState{Dependencies: []string{"bar", "foo"}},
+			&ResourceState{Dependencies: []string{"foo", "bar"}},
+		},
+
+		// Different primaries
+		{
+			false,
+			&ResourceState{Primary: nil},
+			&ResourceState{Primary: &InstanceState{ID: "foo"}},
+		},
+
+		{
+			true,
+			&ResourceState{Primary: &InstanceState{ID: "foo"}},
+			&ResourceState{Primary: &InstanceState{ID: "foo"}},
+		},
+
+		// Different tainted
+		{
+			false,
+			&ResourceState{
+				Tainted: nil,
+			},
+			&ResourceState{
+				Tainted: []*InstanceState{
+					&InstanceState{ID: "foo"},
+				},
+			},
+		},
+
+		{
+			true,
+			&ResourceState{
+				Tainted: []*InstanceState{
+					&InstanceState{ID: "foo"},
+				},
+			},
+			&ResourceState{
+				Tainted: []*InstanceState{
+					&InstanceState{ID: "foo"},
+				},
+			},
+		},
+
+		{
+			true,
+			&ResourceState{
+				Tainted: []*InstanceState{
+					&InstanceState{ID: "foo"},
+					nil,
+				},
+			},
+			&ResourceState{
+				Tainted: []*InstanceState{
+					&InstanceState{ID: "foo"},
+				},
+			},
+		},
+	}
+
+	for i, tc := range cases {
+		if tc.One.Equal(tc.Two) != tc.Result {
+			t.Fatalf("Bad: %d\n\n%s\n\n%s", i, tc.One.String(), tc.Two.String())
+		}
+		if tc.Two.Equal(tc.One) != tc.Result {
+			t.Fatalf("Bad: %d\n\n%s\n\n%s", i, tc.One.String(), tc.Two.String())
+		}
+	}
+}
+
+func TestInstanceStateEqual(t *testing.T) {
+	cases := []struct {
+		Result   bool
+		One, Two *InstanceState
+	}{
+		// Nils
+		{
+			false,
+			nil,
+			&InstanceState{},
+		},
+
+		{
+			false,
+			&InstanceState{},
+			nil,
+		},
+
+		// Different IDs
+		{
+			false,
+			&InstanceState{ID: "foo"},
+			&InstanceState{ID: "bar"},
+		},
+
+		// Different Attributes
+		{
+			false,
+			&InstanceState{Attributes: map[string]string{"foo": "bar"}},
+			&InstanceState{Attributes: map[string]string{"foo": "baz"}},
+		},
+
+		// Different Attribute keys
+		{
+			false,
+			&InstanceState{Attributes: map[string]string{"foo": "bar"}},
+			&InstanceState{Attributes: map[string]string{"bar": "baz"}},
+		},
+
+		{
+			false,
+			&InstanceState{Attributes: map[string]string{"bar": "baz"}},
+			&InstanceState{Attributes: map[string]string{"foo": "bar"}},
+		},
+	}
+
+	for i, tc := range cases {
+		if tc.One.Equal(tc.Two) != tc.Result {
+			t.Fatalf("Bad: %d\n\n%s\n\n%s", i, tc.One.String(), tc.Two.String())
+		}
+	}
+}
+
 func TestInstanceState_MergeDiff(t *testing.T) {
 	is := InstanceState{
 		ID: "foo",