Stop using MustCompile, and instead return an error if any regex fails to compile

[veqryn]

The use of regex.MustCompile (see:

uap-go/uaparser/parser.go

Lines 354 to 360 in daf92ba

	func compileRegex(flags, expr string) *regexp.Regexp {
	if flags == "" {
	return regexp.MustCompile(expr)
	} else {
	return regexp.MustCompile(fmt.Sprintf("(?%s)%s", flags, expr))
	}
	}

) means that if any regex fails, there is a panic.

We pull down the master regex url daily, so that our regexes are always up to date, and load it right into our servers. The panic cause all our servers to crash last night, until we pinned the master regex url to a working version.

NewFromBytes already has the option to return an error, so why not return the error there?

uap-go/uaparser/parser.go

Lines 209 to 219 in daf92ba

	func NewFromBytes(data []byte) (*Parser, error) {
	var definitions RegexesDefinitions
	if err := yaml.Unmarshal(data, &definitions); err != nil {
	return nil, err
	}
	parser := &Parser{definitions, 0, 0, 0, (EOsLookUpMode|EUserAgentLookUpMode|EDeviceLookUpMode), false, false}
	parser.mustCompile()
	return parser, nil
	}

I agree!
@elsigh would you consider a merge request changing the panics to correct error handling (also in NewFromSaved)?

(it's a breaking change)

[yehaotong]

regex.MustCompile 的使用（见：

uap-go/uaparser/parser.go

Lines 354 to 360 in daf92ba

	func compileRegex(flags, expr string) *regexp.Regexp {
	if flags == "" {
	return regexp.MustCompile(expr)
	} else {
	return regexp.MustCompile(fmt.Sprintf("(?%s)%s", flags, expr))
	}
	}

) 意味着如果任何正则表达式失败，就会出现恐慌。
我们每天下拉主正则表达式网址，以便我们的正则表达式始终是最新的，并将其直接加载到我们的服务器中。恐慌导致我们所有的服务器昨晚崩溃，直到我们将主正则表达式 url 固定到一个工作版本。

NewFromBytes 已经可以选择返回错误，那么为什么不在那里返回错误呢？

uap-go/uaparser/parser.go

Lines 209 to 219 in daf92ba

	func NewFromBytes(data []byte) (*Parser, error) {
	var definitions RegexesDefinitions
	if err := yaml.Unmarshal(data, &definitions); err != nil {
	return nil, err
	}
	parser := &Parser{definitions, 0, 0, 0, (EOsLookUpMode|EUserAgentLookUpMode|EDeviceLookUpMode), false, false}
	parser.mustCompile()
	return parser, nil
	}

I want to ask you if this error will cause the program to hang up directly without any error log. My program also uses client: = parser.parse, and hang up directly without any error log during operation, which makes me wonder where there is a bug

[elsigh]

I'm happy to accept a breaking change, but one issue really is that I'm not using this library in prod atm so I'd rather find someone else who can manage/own such a change.. Interested @skerkour ?

Hello,
Unfortunately I absolutely don't have the bandwidth available to own the change.

Kind regards