revert: "fix: fix assign value stand as default (#30651)"

[QuantumGhost]

Reverts #30651

The original fix seems correct on its own. However, for chatflows with multiple answer nodes, the message_replace command only preserves the output of the last executed answer node.

The follow DSL is an example:

DSL

app:
  description: ''
  icon: 🤖
  icon_background: '#FFEAD5'
  mode: advanced-chat
  name: muitiple-answer-streaming
  use_icon_as_answer_icon: false
dependencies: []
kind: app
version: 0.5.0
workflow:
  conversation_variables: []
  environment_variables: []
  features:
    file_upload:
      allowed_file_extensions:
      - .JPG
      - .JPEG
      - .PNG
      - .GIF
      - .WEBP
      - .SVG
      allowed_file_types:
      - image
      allowed_file_upload_methods:
      - local_file
      - remote_url
      enabled: false
      fileUploadConfig:
        attachment_image_file_size_limit: 2
        audio_file_size_limit: 50
        batch_count_limit: 5
        file_size_limit: 15
        file_upload_limit: 10
        image_file_batch_limit: 10
        image_file_size_limit: 10
        single_chunk_attachment_limit: 10
        video_file_size_limit: 100
        workflow_file_upload_limit: 10
      image:
        enabled: false
        number_limits: 3
        transfer_methods:
        - local_file
        - remote_url
      number_limits: 3
    opening_statement: ''
    retriever_resource:
      enabled: true
    sensitive_word_avoidance:
      enabled: false
    speech_to_text:
      enabled: false
    suggested_questions: []
    suggested_questions_after_answer:
      enabled: false
    text_to_speech:
      enabled: false
      language: ''
      voice: ''
  graph:
    edges:
    - data:
        isInIteration: false
        isInLoop: false
        sourceType: start
        targetType: answer
      id: 1767856713829-source-1767856720538-target
      source: '1767856713829'
      sourceHandle: source
      target: '1767856720538'
      targetHandle: target
      type: custom
      zIndex: 0
    - data:
        isInIteration: false
        isInLoop: false
        sourceType: start
        targetType: code
      id: 1767856713829-source-1767856724231-target
      source: '1767856713829'
      sourceHandle: source
      target: '1767856724231'
      targetHandle: target
      type: custom
      zIndex: 0
    - data:
        isInLoop: false
        sourceType: code
        targetType: answer
      id: 1767856724231-source-answer-target
      source: '1767856724231'
      sourceHandle: source
      target: answer
      targetHandle: target
      type: custom
      zIndex: 0
    nodes:
    - data:
        selected: false
        title: User Input
        type: start
        variables: []
      height: 73
      id: '1767856713829'
      position:
        x: 79
        y: 282
      positionAbsolute:
        x: 79
        y: 282
      selected: true
      sourcePosition: right
      targetPosition: left
      type: custom
      width: 242
    - data:
        answer: Answer 1
        selected: false
        title: Answer
        type: answer
        variables: []
      height: 100
      id: answer
      position:
        x: 680
        y: 303
      positionAbsolute:
        x: 680
        y: 303
      selected: false
      sourcePosition: right
      targetPosition: left
      type: custom
      width: 242
    - data:
        answer: Answer 2
        selected: false
        title: Answer 2
        type: answer
        variables: []
      height: 100
      id: '1767856720538'
      position:
        x: 378
        y: 411
      positionAbsolute:
        x: 378
        y: 411
      selected: false
      sourcePosition: right
      targetPosition: left
      type: custom
      width: 242
    - data:
        code: "\ndef main():\n    import time\n    time.sleep(1)\n    return {\n \
          \   }\n"
        code_language: python3
        outputs: {}
        selected: false
        title: Code
        type: code
        variables: []
      height: 52
      id: '1767856724231'
      position:
        x: 387
        y: 303
      positionAbsolute:
        x: 387
        y: 303
      selected: false
      sourcePosition: right
      targetPosition: left
      type: custom
      width: 242
    viewport:
      x: 235.59889940157154
      y: -27.649150847507997
      zoom: 1.0139594797900295
  rag_pipeline_variables: []

[gemini-code-assist]

Summary of Changes

Hello @QuantumGhost, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request performs a full revert of a prior fix, specifically removing functionality in the advanced chat pipeline that handled dynamic updates to the ANSWER node's output. The reverted code previously ensured that if an ANSWER node's final output changed due to variable assignments during workflow execution, the UI would receive an update. Along with the core logic, all associated unit tests for this feature have also been removed, effectively rolling back the entire change.

Highlights

• Revert of Previous Fix: This pull request fully reverts the changes introduced in langgenius/dify#30651, which aimed to fix an issue related to assigning default values.
• Removal of ANSWER Node Logic: The logic within _handle_node_succeeded_event that checked for discrepancies between an ANSWER node's final output and the accumulated task_state.answer has been removed. This logic was responsible for sending message_replace events to the UI when variables were updated during workflow execution.
• Removal of Associated Unit Tests: The dedicated unit test file test_generate_task_pipeline_answer_node.py, which covered various scenarios for the ANSWER node's message_replace logic, has been entirely removed.

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[gemini-code-assist]

Code Review

This pull request reverts a previous change that added logic to update the final answer in advanced chat applications after streaming. The changes consist of removing the specific logic for ANSWER nodes from _handle_node_succeeded_event in generate_task_pipeline.py and deleting the corresponding test file. The revert is implemented cleanly, with both the feature code and its dedicated tests being removed. I find no issues with the implementation of this revert.