[meta] Code health for filesystem interaction.

[ericsnowcurrently]

TODO: maybe move the list of tasks to a wiki page?

Tasks

filesystem:

• identify all current filesystem usage
  • find direct usage
    • (#7519) fs module
    • (#7519) fs-extra module
  • find indirect usage
    • (#7519) tmp module
    • (#7519) glob module
    • ...
  • there are probably some we have missed
• consolidate all filesystem usage into IFileSystem (src/client/common/platform/filesystem.ts)
  • (#7519) add ... to IFileSystem
    • implement
    • update call sites
  • ...
  • drop unused methods from IFileSystem (and friends)
    • (#7519) pathExistsSync()
    • ...
  • how to deal with third-party modules that use the filesystem directly?
• ensure we keep using only our wrapper in the future
  • how to keep from accidentally using the filesystem directly?
• use the new vscode.workspace.fs API (see [meta] Use the vscode filesystem API for *all* filesystem operations. #8533)
• improve testability (and other cleanup)
  • (#7519) factor out TempFileSystem for tmp file/dir ops (i.e. as a wrapper around the node tmp module)
  • (#7519) factor out RawFileSystem
  • (#7519) factor out FileSystemUtils from FileSystem (and use RawFileSystem in it)
  • eliminate IFileSystem in favor of IFileSystemUtils (incl. its raw property)

paths:

• improve testability (and other cleanup)
  • move IPathUtils from src/client/common/types.ts to src/client/common/platform/types.ts
  • (#7519) factor out FileSystemPaths as wrapper around 'path' module
  • rename src/client/common/platform/pathutils.ts to fspaths.ts
  • move FileSystemPaths there (for the low-level operations)
  • rename PathUtils to FileSystemPathUtils (for high-level operations)
  • move low-level operations to IFileSystemPaths
    • separator -> sep
    • delimiter
    • basename()
  • move high-level operations to IFileSystemPathUtils
    • arePathsSame()
  • add IFileSystemPathUtils.raw to expose FileSystemPaths
• identify all current node path module usage
  • find direct usage (see [meta] Consolidate filesystem path operations. #8541)
  • find indirect usage
  • there are probably some we have missed
• consolidate all fs path operations into FileSystemPathUtils & raw (see [meta] Consolidate filesystem path operations. #8541)
  • how to deal with third-party modules that use node's "path" module directly?
• ensure we keep using only our wrapper in the future (see [meta] Consolidate filesystem path operations. #8541)
  • how to keep from accidentally using node's "path" module directly?

other:

• clean up (particularly for testability)
  • move IsWindows from src/client/common/types.ts to src/client/common/platform/types.ts

[luabud]

Closing as stale.