[ML] Using model supplied mask token (elastic#162168)

Fixes elastic#159577

Using the `mask_token` property from the model config for testing the
model.
This is shown in the input placeholder text, in the input validation and
for displaying the results.

<img width="433" alt="image"
src="https://github.com/elastic/kibana/assets/7405507/bc63f9e6-a3d5-402c-a451-8d80b758acbc">

x-pack/plugins/ml/public/application/model_management/test_models/models/text_classification/fill_mask_inference.ts

@@ -16,7 +16,7 @@ import { getGeneralInputComponent } from '../text_input';
 import { getFillMaskOutputComponent } from './fill_mask_output';
 import { trainedModelsApiProvider } from '../../../../services/ml_api_service/trained_models';
 
-const MASK = '[MASK]';
+const DEFAULT_MASK_TOKEN = '[MASK]';
 
 export class FillMaskInference extends InferenceBase<TextClassificationResponse> {
   protected inferenceType = SUPPORTED_PYTORCH_TASKS.FILL_MASK;
@@ -30,6 +30,7 @@ export class FillMaskInference extends InferenceBase<TextClassificationResponse>
       defaultMessage: 'Test how well the model predicts a missing word in a phrase.',
     }),
   ];
+  private maskToken = DEFAULT_MASK_TOKEN;
 
   constructor(
     trainedModelsApi: ReturnType<typeof trainedModelsApiProvider>,
@@ -38,9 +39,14 @@ export class FillMaskInference extends InferenceBase<TextClassificationResponse>
     deploymentId: string
   ) {
     super(trainedModelsApi, model, inputType, deploymentId);
+    // @ts-expect-error mask_token is missing in type
+    const maskToken = model.inference_config?.[this.inferenceType]?.mask_token;
+    if (maskToken) {
+      this.maskToken = maskToken;
+    }
 
     this.initialize([
-      this.inputText$.pipe(map((inputText) => inputText.every((t) => t.includes(MASK)))),
+      this.inputText$.pipe(map((inputText) => inputText.every((t) => t.includes(this.maskToken)))),
     ]);
   }
 
@@ -71,16 +77,16 @@ export class FillMaskInference extends InferenceBase<TextClassificationResponse>
 
   public predictedValue(resp: TextClassificationResponse) {
     const { response, inputText } = resp;
-    return response[0]?.value ? inputText.replace(MASK, response[0].value) : inputText;
+    return response[0]?.value ? inputText.replace(this.maskToken, response[0].value) : inputText;
   }
 
   public getInputComponent(): JSX.Element | null {
     if (this.inputType === INPUT_TYPE.TEXT) {
       const placeholder = i18n.translate(
         'xpack.ml.trainedModels.testModelsFlyout.fillMask.inputText',
         {
-          defaultMessage:
-            'Enter a phrase to test. Use [MASK] as a placeholder for the missing words.',
+          defaultMessage: `Enter a phrase to test. Use {maskToken} as a placeholder for the missing words.`,
+          values: { maskToken: this.maskToken },
         }
       );
 

x-pack/plugins/translations/translations/fr-FR.json

@@ -25599,7 +25599,6 @@
     "xpack.ml.trainedModels.nodesList.totalAmountLabel": "Nombre total de nœuds Machine Learning",
     "xpack.ml.trainedModels.testModelsFlyout.deploymentIdLabel": "ID de déploiement",
     "xpack.ml.trainedModels.testModelsFlyout.fillMask.info1": "Testez la capacité du modèle à prédire un mot manquant dans une phrase.",
-    "xpack.ml.trainedModels.testModelsFlyout.fillMask.inputText": "Entrez une expression à tester. Utilisez [MASK] comme espace réservé pour les mots manquants.",
     "xpack.ml.trainedModels.testModelsFlyout.fillMask.label": "Masque de remplissage",
     "xpack.ml.trainedModels.testModelsFlyout.generalTextInput.inputText": "Texte d'entrée",
     "xpack.ml.trainedModels.testModelsFlyout.generalTextInput.inputTitle": "Texte d'entrée",

x-pack/plugins/translations/translations/ja-JP.json

@@ -25598,7 +25598,6 @@
     "xpack.ml.trainedModels.nodesList.totalAmountLabel": "合計機械学習ノード",
     "xpack.ml.trainedModels.testModelsFlyout.deploymentIdLabel": "デプロイID",
     "xpack.ml.trainedModels.testModelsFlyout.fillMask.info1": "モデルがフレーズの不足している単語を予測する精度をテストします。",
-    "xpack.ml.trainedModels.testModelsFlyout.fillMask.inputText": "テストするフレーズを入力してください。足りない語句のプレースホルダーとして[MASK]を使用します。",
     "xpack.ml.trainedModels.testModelsFlyout.fillMask.label": "マスクを塗りつぶす",
     "xpack.ml.trainedModels.testModelsFlyout.generalTextInput.inputText": "入力テキスト",
     "xpack.ml.trainedModels.testModelsFlyout.generalTextInput.inputTitle": "入力テキスト",

x-pack/plugins/translations/translations/zh-CN.json

@@ -25597,7 +25597,6 @@
     "xpack.ml.trainedModels.nodesList.totalAmountLabel": "Machine Learning 节点总数",
     "xpack.ml.trainedModels.testModelsFlyout.deploymentIdLabel": "部署 ID",
     "xpack.ml.trainedModels.testModelsFlyout.fillMask.info1": "测试模型预测短语中缺失的词的表现。",
-    "xpack.ml.trainedModels.testModelsFlyout.fillMask.inputText": "输入短语以进行测试。将 [MASK] 用作缺失词的占位符。",
     "xpack.ml.trainedModels.testModelsFlyout.fillMask.label": "填充掩码",
     "xpack.ml.trainedModels.testModelsFlyout.generalTextInput.inputText": "输入文本",
     "xpack.ml.trainedModels.testModelsFlyout.generalTextInput.inputTitle": "输入文本",