decode backend hash as uint64

Older versions of terraform could save the backend hash number in a
value larger than an int.

While we could conditionally decode the state into an intermediary data
structure for upgrade, or detect the specific decode error and modify
the json, it seems simpler to just decode into the most flexible value
for now, which is a uint64.

command/meta_backend.go

@@ -467,7 +467,7 @@ func (m *Meta) backendFromConfig(opts *BackendOpts) (backend.Backend, tfdiags.Di
 		// settings in the configuration files are unchanged. (The only
 		// record we have of CLI overrides is in the settings cache in this
 		// case, so we have no other source to compare with.
-		if !opts.Init && cHash == s.Backend.Hash {
+		if !opts.Init && uint64(cHash) == s.Backend.Hash {
 			log.Printf("[TRACE] Meta.Backend: using already-initialized, unchanged %q backend configuration", c.Type)
 			return m.backend_C_r_S_unchanged(c, cHash, sMgr)
 		}
@@ -714,7 +714,7 @@ func (m *Meta) backend_C_r_s(c *configs.Backend, cHash int, sMgr *state.LocalSta
 	s.Backend = &terraform.BackendState{
 		Type:      c.Type,
 		ConfigRaw: json.RawMessage(configJSON),
-		Hash:      cHash,
+		Hash:      uint64(cHash),
 	}
 
 	if err := sMgr.WriteState(s); err != nil {
@@ -857,7 +857,7 @@ func (m *Meta) backend_C_r_S_changed(c *configs.Backend, cHash int, sMgr *state.
 	s.Backend = &terraform.BackendState{
 		Type:      c.Type,
 		ConfigRaw: json.RawMessage(configJSON),
-		Hash:      cHash,
+		Hash:      uint64(cHash),
 	}
 
 	if err := sMgr.WriteState(s); err != nil {
@@ -886,8 +886,8 @@ func (m *Meta) backend_C_r_S_unchanged(c *configs.Backend, cHash int, sMgr *stat
 	// it's possible for a backend to be unchanged, and the config itself to
 	// have changed by moving a parameter from the config to `-backend-config`
 	// In this case we only need to update the Hash.
-	if c != nil && s.Backend.Hash != cHash {
-		s.Backend.Hash = cHash
+	if c != nil && s.Backend.Hash != uint64(cHash) {
+		s.Backend.Hash = uint64(cHash)
 		if err := sMgr.WriteState(s); err != nil {
 			diags = diags.Append(err)
 			return nil, diags

terraform/state.go

@@ -656,7 +656,7 @@ func (s *State) String() string {
 type BackendState struct {
 	Type      string          `json:"type"`   // Backend type
 	ConfigRaw json.RawMessage `json:"config"` // Backend raw config
-	Hash      int             `json:"hash"`   // Hash of portion of configuration from config files
+	Hash      uint64          `json:"hash"`   // Hash of portion of configuration from config files
 }
 
 // Empty returns true if BackendState has no state.

terraform/state_test.go

@@ -1561,6 +1561,20 @@ func TestReadState_pruneDependencies(t *testing.T) {
 	}
 }
 
+func TestReadState_bigHash(t *testing.T) {
+	expected := uint64(14885267135666261723)
+	s := strings.NewReader(`{"version": 3, "backend":{"hash":14885267135666261723}}`)
+
+	actual, err := ReadState(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if actual.Backend.Hash != expected {
+		t.Fatalf("expected backend hash %d, got %d", expected, actual.Backend.Hash)
+	}
+}
+
 func TestResourceNameSort(t *testing.T) {
 	names := []string{
 		"a",