Save All doesn't gofmt all files when "go:formatOnSave" flag is true

[lirao]

When I save a bunch of files all at once with Save All, only the active file is formatted, and the rest are saved in their un-fmt'ed state. (Autosave is off)

[lukehoban]

I looked into this, and it appears it isn't possible to fix this with the current VS Code APIs.

This is primarily blocked on microsoft/vscode#239, which would make sure the formatting could be applied before the files are saved to disk.

But it is more directly blocked by seemingly not being able to get a TextEditor to use to apply a set of TextEdits for a TextDocument provided to vscode.workspace.onDidSaveTextDocument. See https://github.com/Microsoft/vscode-go/blob/master/src/goMain.ts#L186.

/cc @egamma and @bpasero in case they have a suggestion for how this could be handled with the current VS Code API.

[bpasero]

I think this needs microsoft/vscode#239 and is a good scenario for having that as API.

[FrenchBen]

It'd be nice to also have:
"go.fmtFlags": [],

edit: Looks like it exists, but no docs:
"go.formatFlags": [],
https://github.com/Microsoft/vscode-go/blob/dca9bef794ba1a40f42a1dff63ab5fe9658e4652/package.json#L270

[ramya-rao-a]

onWillSaveTextDocument API is now available: https://code.visualstudio.com/updates/v1_6#_new-apis

The only catch is that there is a limitation on the time taken for the listeners of this event.
There have been cases where the formatter in the GO extension seem to take a long time (multiple seconds) in which case, they will be eventually ignored: https://github.com/Microsoft/vscode/blob/a6435b1cbd1417b0d334ea9018f5371df198898f/src/vs/vscode.d.ts#L3980

[ramya-rao-a]

Closing in favor of #540 which will fix this issue as well

[ramya-rao-a]

With the work in #540 completed, the latest update to the Go extension (0.6.70) has the fix for this issue.