Support for negative lookbehind regex in app.yaml - google-app-engine

Question

I am trying to exclude all source map files, i.e files ending with .map from being uploaded to app engine.
Here's a snippet of the config in app.yaml file.
handlers:
- url: /(.*\\..+(?\<!map))$
static_files: \\1
upload: /(.*\\..+(?\<!map))$
secure: always
However, when deploying, this is the error that I get.
content <{
"error": {
"code": 400,
"message": "The request is invalid.",
"status": "INVALID_ARGUMENT",
"details": [
{
"#type": "type.googleapis.com/google.rpc.BadRequest",
"fieldViolations": [
{
"field": "version.handlers[0].url_regex",
"description": "Value \"/(.*\\..+(?\\\u003c!map))$\" must be a valid regular expression. Details: invalid or unsupported Perl syntax."
},
{
"field": "version.handlers[0].static_files.upload_path_regex",
"description": "Value \"/(.*\\..+(?\\\u003c!map))$\" must be a valid regular expression. Details: invalid or unsupported Perl syntax."
}
]
}
In the app.yaml reference documentation, it implies that it supports POSIX extended regular expression syntax.
Might anyone advice on what should be done to fix this.

Answer 1

You can use
^(.*([^.].{3}|.[^m].{2}|.{2}[^a].|.{3}[^p])|.{0,3})$
See the regex demo. Details:
^ - start of string
(.*([^.].{3}|.[^m].{2}|.{2}[^a].|.{3}[^p])|.{0,3}) - Group 1 matching:
.*([^.].{3}|.[^m].{2}|.{2}[^a].|.{3}[^p]) - any text, and then any of
[^.].{3}| - a char other than a . and then any 3 chars, or
.[^m].{2}| - any char, a char other than m, and then any two chars, or
.{2}[^a].| - any two chars, any char other than a, and then any one char
.{3}[^p] - any three chars, and then a char other than p
| - or
.{0,3} - any zero, one, two or three chars.
$ - end of string.