Bad regex for Lambda S3Bucket Definition about aws2openapi HOT 11 CLOSED

Bad in what sense? It seems to be a valid ECMA-262 regex.

In the original AWS definition it was

{ "pattern":"^[0-9A-Za-z\\.\\-_]*(?<!\\.)$" }

and the output yaml is

pattern: '^[0-9A-Za-z\.\-_]*\(\?<!\.\)$'

So it may have been mangled by convertRegex.

https://github.com/Mermade/aws2openapi/blob/5c3208167355eb8949e224add24fb0a770189d48/index.js#L183-L209

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I'm not sure - as their format is undocumented, but I've assumed it's POSIX BRE.

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Use of native JS RegExp here

https://github.com/aws/aws-sdk-js/blob/c108474595ec8714f97e47439090bc775fb76a25/lib/param_validator.js#L161-L169

Seems to indicate it should be a standard ECMA 262 RegExp... but if it was mangled by convertRegex that means the RegExp constructor throws on it:

SyntaxError: Invalid regular expression: /^[0-9A-Za-z.-_]*(?<!.)$/: Invalid group

Perhaps all we can do is report it upstream?

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If the original regexen are ECMA 262 already, why is convertRegex necessary?

The regex works properly in the aws-sdk, but the regex in their JSON does indeed throw an invalid group when passed to the RegExp constructor...

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If the original regexen are ECMA 262 already, why is convertRegex necessary?

Because a number of patterns in the AWS json files throw errors in the RegExp constructor* and I assumed it was because they were POSIX BREs not ECMA 262 REs. I think the first example I found showed up as BRE syntax in some tool or other.

*and I wanted the resultant OpenAPI definitions to pass validation.

Can you debug the SDK and see if/how it is managing to instantiate the regex?

The lambda client appears to the load the min version of the API definition, not the normal one, and the min version doesn't contain any pattern properties (or descriptions, or ...).

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It looks like the JS client doesn't do any client-side validation actually. Invalid regexen still get sent to the server, which responds with:

{"message":"1 validation error detected: Value 'foo&*' at 'code.s3Bucket' failed to satisfy constraint: Member must satisfy regular expression pattern: ^[0-9A-Za-z\\.\\-_]*(?<!\\.)$"}

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According to this cheatsheet, the regex in question is a negative look-behind which says that the string can't end in a ., so foo- is legal but not foo..

I don't think JS has an equivalent to negative lookbehinds. I think the best solution is to strip the negative lookbehind, which would result in a regex that's more permissive than it should be, but would at least pass for valid strings.

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If you're good with that solution I can send a PR

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That would be great, thanks.

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I think we can close this?

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