--stats-json doesn't work with --watch

[mark-buer]

Repro steps

• Compare result of running ng --watch --stats-json
• to the result of running ng --stats-json

Observed behavior

ng --stats-json produces a stats.json file.
ng --watch --stats-json does not produce a stats.json file.

Desired behavior

It should be possible to watch and to produce the stats.json file.

If this is not possible, and these two flag settings are mutually exclusive, it'd be nice if --help or wiki mentioned it.

Usecase:

I'm developing a custom build system for an electron application which is comprised of many angular apps. ng --watch speeds up our development cycle, but the initial hit of building many apps at application startup is a killer. I plan to use the output of prior --watch --stats-json builds to fingerprint the filesystem, and thus only perform a build if the modified time of any of the modules of an angular app have changed.

Thus, I'd like stats.json to be emitted every time that the webpack compiler callback is invoked.

Mention any other details that might be useful

I can't think of a good reason why stats.json isn't emitted during --watch builds.
Relevant code location https://github.com/angular/angular-cli/blob/master/packages/%40angular/cli/tasks/build.ts#L61

[mark-buer]

This problem was briefly mentioned here: #6131 (comment)

[filipesilva]

It's a bug for sure, just a rather low prio one. Instead of writing the stats there we should be using something like https://www.npmjs.com/package/stats-webpack-plugin.

[mgechev]

Looks like a problem with old version of the CLI. Let us close the issue for now. If it's still relevant, please open a new ticket with steps to reproduce and a minimal demo. Thanks!

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