terraform: sort dependencies of resource state [GH-928]

CHANGELOG.md

@@ -35,6 +35,7 @@ BUG FIXES:
   * core: Fix crash that could occur when there are exactly zero providers
       installed on a system. [GH-786]
   * core: JSON TF configurations can configure provisioners. [GH-807]
+  * core: Sort `depends_on` in state to prevent unnecessary file changes. [GH-928]
   * command/apply: Won't try to initialize modules in some cases when
       no arguments are given. [GH-780]
   * command/apply: Fix regression where user variables weren't asked [GH-736]

terraform/state.go

@@ -156,6 +156,11 @@ func (s *State) prune() {
 // sort sorts the modules
 func (s *State) sort() {
 	sort.Sort(moduleStateSort(s.Modules))
+
+	// Allow modules to be sorted
+	for _, m := range s.Modules {
+		m.sort()
+	}
 }
 
 func (s *State) GoString() string {
@@ -347,6 +352,12 @@ func (m *ModuleState) prune() {
 	}
 }
 
+func (m *ModuleState) sort() {
+	for _, v := range m.Resources {
+		v.sort()
+	}
+}
+
 func (m *ModuleState) GoString() string {
 	return fmt.Sprintf("*%#v", *m)
 }
@@ -515,6 +526,10 @@ func (r *ResourceState) prune() {
 	r.Tainted = r.Tainted[:n]
 }
 
+func (r *ResourceState) sort() {
+	sort.Strings(r.Dependencies)
+}
+
 func (s *ResourceState) GoString() string {
 	return fmt.Sprintf("*%#v", *s)
 }