Remove 's' regex flag from extended JSON

[devkev]

I tested the mongo shell of every stable version between 1.6.0 and 3.2.0, and none support 's' as a valid flag.

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This change is 

[kay-kim]

Hey @devkev --
I'm able to use the s flag.
~/Mongo $ ./mongodb-3.2.4/bin/mongoexport -d test -c products --query '{ description: /m.*line/si }'
2016-05-02T10:33:59.813-0400 connected to: localhost
{"_id":102.0,"sku":"xyz456","description":"Many spaces before line"}
{"_id":103.0,"sku":"xyz789","description":"Multiple\nline description"}
2016-05-02T10:33:59.813-0400 exported 2 records
~/Mongo $ ./mongodb-3.2.4/bin/mongoexport -d test -c products --query '{ description: /m.*line/i }'
2016-05-02T10:34:04.620-0400 connected to: localhost
{"_id":102.0,"sku":"xyz456","description":"Many spaces before line"}
2016-05-02T10:34:04.620-0400 exported 1 record

[devkev]

Ugh. This has made me realise that this is actually a much bigger problem.

The issue is that mongo server/shell uses SpiderMonkey (in 3.2+, earlier versions use V8), whereas the tools use Golang - and each of these has their own RegExp implementations, with slight variations in the accepted flags. eg, in addition to the normal g, i, m:

• SpiderMonkey has u, y:
  • https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/RegExp#Parameters
• Golang uses RE2, which has s, U (but not g)
  • https://golang.org/pkg/regexp/#pkg-overview
  • https://github.com/google/re2/wiki/Syntax

So this now feels like it deserves a DOCS ticket, rather than a "drive-by pull request".

[kay-kim]

Hey Kevin --
will close this. We do have a docs ticket https://jira.mongodb.org/browse/DOCS-11478 to update the page. Will see how to handle aforementioned issue when doing the ticket.