Add TS server command for removing all unused code in a file

Search terms

• code action
• source action
• getCombinedCodeFix

Feature request

Add a new TS Server command that removes all unused code in a file. This should only perform 'safe' removals, such as:

• Unreachable code
• Unused imports
• Unused declarations

We should likely not remove unused parameters. Not sure about removing unused variable since removing them can also have side effects

Use case

VS Code allows users to configure code actions that are run on save. One of the supported code actions is source.removeUnused which attempts to remove unused code in a file

On the VS Code side, we can't implement this very well since unused code often ends up overlapping with other unused code and we don't have much insight into what is "safe" to remove and what is not

首先阅读现有的 TS Server 命令和 issue 中提到的 getCombinedCodeFix 路径，然后比较 VS Code 如何调用 source.removeUnused。完成的标准是：某个命令只移除安全的不可达代码、未使用的 import 和未使用的声明，同时保留参数和可能具有副作用的变量不变。