feat: add --json-file-output option for snyk test

[maxjeffos]

• Ready for review
• Follows CONTRIBUTING rules
• Reviewed by Snyk internal team

What does this PR do?

This allows a user to directly save JSON format output to a file as specified by the --json-file-output= parameter, regardless of whether they are using the human-readable or json output. The primary use-case of this is to enable users (and Snyk CI plugins) to simultaneously get the human readable output while saving a JSON format output to a file for other purposes (for example, generating a report).

Where should the reviewer start?

Please take a look at the code and advise as to testing best-practices. I will then include appropriate tests for this PR.

How should this be manually tested?

Say you want to save the JSON output to a file called "snyk-output.json" in the current directory. You could then run snyk test --json-file-output=snyk-output.json which should do a normal snyk test and generate the human-readable output to stdout but at the same time save the JSON format output to snyk-output.json.

Any background context you want to provide?

We need this for #1027 and snyk/snyk-azure-pipelines-task#30 as well as for another CI plugin we're currently working on.
This PR replaces a #1059 which I will close once this gets traction

What are the relevant tickets?

• https://github.com/snyk/snyk/issues/1027
• https://github.com/snyk/snyk-azure-pipelines-task/issues/30

Additional questions

[aarlaud]

@maxjeffos can you also make sure the output of --print-deps is in that file too if the option is specified. I'm using the depgraph for something and that'd be great to have in this function. Thanks!

[gitphill]

potentially 'ugly' for user

for example: snyk test --json-file-output (no path provided) produces:

TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string or an instance of Buffer or URL. Received type boolean (true)
    at Object.openSync (fs.js:450:10)
    at Object.writeFileSync (fs.js:1279:35)
    at saveJsonResultsToFile (/Users/phill/code/snyk/src/cli/index.ts:156:5)
    at handleError (/Users/phill/code/snyk/src/cli/index.ts:111:5)
    at main (/Users/phill/code/snyk/src/cli/index.ts:273:28)
    at processTicksAndRejections (internal/process/task_queues.js:97:5) {
  code: 'ERR_INVALID_ARG_TYPE'
}

[gitphill]

maybe some validation of argument passed?

[maxjeffos]

This is resolved now and I added some tests for it. Thanks.

[gitphill]

can we update help text please?

[gitphill]

should we support a path to json?

for example: snyk test ---json-file-output=path/to/ouput.json at the moment this causes ENOENT error

If we don't want to support this, we should validate input and display friendly message explaining arg should be filename only (no path).

[gitphill]

"--json-output-file should be a filename path"

[maxjeffos]

👍

[snyksec]

🎉 This PR is included in version 1.332.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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