[iOS] Add "shouldReplaceText" API

platforms/ios/lib/WysiwygComposer/Sources/WysiwygComposer/Components/WysiwygComposerView/WysiwygComposerViewModel.swift

@@ -64,6 +64,10 @@ public class WysiwygComposerViewModel: WysiwygComposerViewModelProtocol, Observa
         }
     }
 
+    /// Whether the composer should take any keyboard input.
+    /// When set to `false`, `replaceText(range:replacementText:)` returns `false` as well.
+    public var shouldReplaceText = true
+
     /// Published value for the composer plain text mode.
     @Published public var plainTextMode = false {
         didSet {
@@ -289,6 +293,10 @@ public extension WysiwygComposerViewModel {
     }
 
     func replaceText(range: NSRange, replacementText: String) -> Bool {
+        guard shouldReplaceText else {
+            return false
+        }
+
         guard !plainTextMode else {
             return true
         }

platforms/ios/lib/WysiwygComposer/Tests/WysiwygComposerTests/Components/WysiwygComposerView/WysiwygComposerViewModelTests.swift

@@ -19,16 +19,13 @@ import Combine
 import XCTest
 
 final class WysiwygComposerViewModelTests: XCTestCase {
-    let viewModel = WysiwygComposerViewModel()
+    var viewModel: WysiwygComposerViewModel!
 
     override func setUpWithError() throws {
+        viewModel = WysiwygComposerViewModel()
         viewModel.clearContent()
     }
 
-    override func tearDownWithError() throws {
-        viewModel.plainTextMode = false
-    }
-
     func testIsContentEmpty() throws {
         XCTAssertTrue(viewModel.isContentEmpty)
 
@@ -51,6 +48,13 @@ final class WysiwygComposerViewModelTests: XCTestCase {
         XCTAssertTrue(shouldChange)
     }
 
+    func testSimpleTextInputIsNotAccepted() throws {
+        viewModel.shouldReplaceText = false
+        let shouldChange = viewModel.replaceText(range: .zero,
+                                                 replacementText: "A")
+        XCTAssertFalse(shouldChange)
+    }
+
     func testNewlineIsNotAccepted() throws {
         let shouldChange = viewModel.replaceText(range: .zero,
                                                  replacementText: "\n")