保持向前兼容

Once projects exist using your extension, it is critical that you do not change the extension in ways that will break compatibility as doing so will effectively corrupt projects.

你最好别动什么

永远别动扩展 ID

  getInfo() {
    return {
      // 别动，不然用你扩展的作品就全坏了！！！
      id: 'fetch'
      // ...
    };
  }

永远别动积木的 opcode 和积木类型

Instead, create a new block and mark the old one as hideFromPalette: true.

It is generally safe to change blockType from REPORTER to BOOLEAN or from HAT to EVENT, but a conversion of HAT to BOOLEAN would be problematic.

  getInfo() {
    return {
      // ...
      blocks: [
        {
          // 别删，不然用这个积木的作品就别想编辑作品了！！！
          blockType: Scratch.BlockType.REPORTER,
          opcode: "fetch",
          // ...
        }
      ]
    };
  }

永远别删积木

Instead, create a new block and mark the old one as hideFromPalette: true.

  getInfo() {
    return {
      // ...
      blocks: [
        // 别删，不然用这个积木的作品就全坏了！！！
        {
          opcode: "old",
          hideFromPalette: true
          // ...
        }
      ]
    };
  }

永远别动参数 ID 和类型

  getInfo() {
    return {
      // ...
      blocks: [
        {
          // THE ARGUMENT ID "INPUT" MUST NEVER BE CHANGED OR REMOVED
          text: "block [INPUT]",
          arguments: {
            INPUT: {
              type: Scratch.ArgumentType.REPORTER,
              // ...
            }
          },
          // ...
        }
      ]
    };
  }

永远别往已经存在的积木加参数

Instead, create a new block and mark the old one as hideFromPalette: true. The new block can be reimplemented in terms of the old one:

  getInfo() {
    return {
      // ...
      blocks: [
        {
          blockType: Scratch.BlockType.REPORTER,
          id: "oldBlock",
          text: "old [INPUT1]",
          arguments: {
            INPUT1: { /* ... */ }
          },
          hideFromPalette: true
        },
        {
          blockType: Scratch.BlockType.REPORTER,
          opcode: "newBlock",
          text: "new [INPUT1] [INPUT2]",
          arguments: {
            INPUT1: { /* ... */ },
            INPUT2: { /* ... */ }
          }
        }
      ]
    };
  }
  oldBlock(args) {
    return this.newBlock({
      ...args,
      INPUT2: "Default value"
    });
  }
  newBlock(args) {
    // ...
  }

别动 isTerminal

If a COMMAND block does not already have isTerminal: true, then don't add it as doing so will cause existing projects that connect blocks underneath to break. Instead, create a new block and optionally hide the old one.

别动 acceptReporters

Converting an input menu to a field menu and vice-versa does not work and will corrupt projects. Create a new menu and block instead.

别显著修改积木的行为

Trivial bug fixes are typically fine, but significant changes may break projects. This is a bit harder to quantify; the best way to make sure your changes don't break projects is extensive testing.

你可以动什么

You can always change these parts of extension metadata:

• name
• docsURI
• color1, color2, color3
• menuIconURI and blockIconURI

You can always change these parts of blocks and arguments:

• text, as long as it contains the same arguments (changing argument order is safe)
• disableMonitor (enabling true just hides checkmark, does not remove existing monitors)
• hideFromPalette
• filter (adding filter just hides from palette, does not remove existing blocks)
• defaultValue
• dataURI and flipRTL in image inputs

For menus, you can always change text, but you should not change value without careful consideration. Adding menu items is always okay, but removing menu items is dangerous.

万一我就是非得动不可呢？

There are times when there is no option but to break backward compatibility. In these instances, you should create a brand new extension with an entirely new ID and leave the old version untouched.

For example, if your extension fetch needs a complete redesign, you could create a new extension with the ID fetch2.

下一步

Next, let's learn how to share your extension with the world.