The View does't update after the state is changed.

[IDTIMW]

This is my state code, where submit ButtonDisabled is used to calculate whether the button is disabled or not. This is mainly based on whether the tagName of the corresponding input box is not empty.

struct TagEditorState: Equatable {
  @BindableState var tagName = ""
  @BindableState var focusedField: Field?

  var submitButtonDisabled: Bool {
    self.tagName.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty
  }
}

This part of the code is my submit button, where the disabled part does not become available based on my input. What is the problem and how should I change my code?

var submitButton: some View {
    WithViewStore(self.store) { viewStore in
      Button(action: {
        viewStore.send(.submitButtonTapped)
      }, label: {
        Text(viewStore.tag == nil ? "button.submit".localized() : "button.save".localized())
      })
      .buttonStyle(PrimaryButtonStyle())
      .disabled(viewStore.submitButtonDisabled)
      .sheet(isPresented: viewStore.binding(get: \.membershipIntroductionSheetIsPresented, send: TagEditorAction.setMembershipIntroductionSheet(isPresented: ))) {
        MembershipIntroductionSheet()
      }
    }
  }

[tgrapperon]

Nothing stands particularly out in what you're showing, excepted that there is no .tag in TagEditorState, so we might be missing problematic bits elsewhere. This view's Button should be disabled or enabled when tagName changes from empty to non-empty. So I would make sure that this value is indeed changing. The PrimaryButtonStyle is also maybe participating to give the impression that the Button is not disabled. If this is a custom ButtonStyle, you should probably expose an @Environment(\.isEnabled) var isEnabled in your modifier, and adapt styling accordingly.
So I would test the issue by simply removing the styling to begin with, and check if this is only a styling issue.
Assuming this ViewStore is indeed operating on a complete TagEditorState, I would also initially put a Text("\(viewStore.tagName.count)") somewhere to check what it sees.