the example `1.2.3-alpha.10.beta.0+build.unicorn.rainbow` in README is no longer valid

[KagamiChan]

node
Welcome to Node.js v12.6.0.
Type ".help" for more information.
> const semverRegex = require('semver-regex')
undefined
> semverRegex().test('1.2.3-alpha.10.beta.0+build.unicorn.rainbow')
false
> semverRegex().test('1.2.3-alpha.0')
false
> semverRegex().test('1.2.3-alpha.1')
true

while in semver package, .0 is considered correct and in npm doc we can see this usage

[KagamiChan]

after looking at the history I think #15 is related, then we need to update the example and it will be great to add some notes and an example

[KagamiChan]

But I don't think the mentioned semver clause 9 forbids this because their grammar as well as the given regex suggest that alpha.0 is still valid

@stroncium

[stroncium]

@KagamiChan Sorry it took so long to answer.

Quoting https://semver.org/,

9. A pre-release version MAY be denoted by appending a hyphen and a series of dot separated identifiers immediately following the patch version. Identifiers MUST comprise only ASCII alphanumerics and hyphen [0-9A-Za-z-]. Identifiers MUST NOT be empty. Numeric identifiers MUST NOT include leading zeroes. Pre-release versions have a lower precedence than the associated normal version. A pre-release version indicates that the version is unstable and might not satisfy the intended compatibility requirements as denoted by its associated normal version. Examples: 1.0.0-alpha, 1.0.0-alpha.1, 1.0.0-0.3.7, 1.0.0-x.7.z.92.

From RFC2119:

2. MUST NOT This phrase, or the phrase "SHALL NOT", mean that the
   definition is an absolute prohibition of the specification.

Also, looking into BNF(available at https://semver.org/ too):

<valid semver> ::= <version core>
                 | <version core> "-" <pre-release>
                 | <version core> "+" <build>
                 | <version core> "-" <pre-release> "+" <build>

<pre-release> ::= <dot-separated pre-release identifiers>

<dot-separated pre-release identifiers> ::= <pre-release identifier>
                                          | <pre-release identifier> "." <dot-separated pre-release identifiers>

<pre-release identifier> ::= <alphanumeric identifier>
                           | <numeric identifier>

<numeric identifier> ::= "0"
                       | <positive digit>
                       | <positive digit> <digits>

<digit> ::= "0"
          | <positive digit>

<positive digit> ::= "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"

I don't think there is a chance of me misunderstanding specification.

[KagamiChan]

Hi @stroncium

Thanks for your reply

I think you're referring "must not include leading zeros", but a single zero does not seem to apply to this case, otherwise we cannot express the 0 itself

and in the BNF, <numeric identifier> has a special case "0", which could be filled into the <dot-separated pre-release identifiers>

In fact, the suggested regexp in semver.org also allows the form '1.0.0-beta.0', you may try this regex in regex101 via the link in the answer

[stroncium]

@KagamiChan Oh hell, sorry. I actually read though this BNF like 5 times when implementing original patch and twice while replying to this issue, and every damn time I managed to overlook this cunning "0" option for <numeric identifier>

[KagamiChan]

Thanks for you quick fix!