Find :: outside of markdown code formatting - regex

Question

I have a bunch of markdown files, where I want to search for Ruby's double colon :: outside of some code formatting (e.g. where I forgot to apply proper markdown). For example
`foo::bar`
hello `foo::bar` test
` example::with::whitespace `
```
Proper::Formatted
```
```
Module::WithIndendation
```
```
Some::Nested::Modules
```
```ruby
CodeBlock::WithSyntax
```
# Some::Class
## Another::Class Heading
some text
The regex only should match Some::Class and Another::Class, because they miss the surrounding backticks, and are also not within a multiline code fence block.
I have this regex, but it also matches the multi line block
[\s]+[^`]+(::)[^`]+[\s]?
Any idea, how to exclude this?
EDIT:
It would be great, if the regex would work in Ruby, JS and on the command line for grep.

Answer 1

For the original input, you may use this regex in ruby to match :: string
not preceded by a ` and
not preceded by ` followed a white-space:
Regex:
(?<!`\s)(?<!`)\b\w+::\w+
RegEx Demo 1
RegEx Breakup:
(?<!\s): Negative lookbehind to assert that <code> and whitespace is not at preceding position
(?<!): Negative lookbehind to assert that <code> is not at preceding position
\b: Match word boundary
\w+: Match 1+ word characters
::: Match a ::
\w+: Match 1+ word characters
You can use this regex in Javascript:
(?<!`\w*\s*|::)\b\w+(?:::\w+)+
RegEx Demo 2
For gnu-grep, consider this command:
grep -ZzoP '`\w*\s*\b\w+::\w+(*SKIP)(*F)|\b\w+::\w+' file |
xargs -0 printf '%s\n'
Some::Class
Another::Class
RegEx Demo 3

Answer 2

One can use the regular expression
rgx = /`[^`]*`|([^`\r\n]*::[^`\r\n]*)/
with the form of String#gsub that takes one argument and no block, and therefore returns an enumerator (str holding the example string given in the question):
str.gsub(rgx).select { $1 }
#=> ["# Some::Class", "## Another::Class Heading"]
The idea is that the first part of the regex's alternation, `[^`]*`, matches, but does not capture, all strings delimited by backtics (including ``), whereas the second part, ([^`\r\n]*::[^`\r\n]*), matches and captures all strings on a single line that contain '::' but no backtics. We therefore concern ourselves with captures only, by invoking select { $1 } on the enumerator returned by gsub.
The regular expression can be made self-documenting by writing it in free-spacing mode.
rgx = /
` # match a backtic
[^`]* # match zero of more characters other than backtics
` # match a backtic
| # or
( # begin capture group 1
[^`\r\n]* # match zero of more characters other than backtics and
# line terminators
:: # match two colons
[^`\r\n]* # ditto line before previous
) # end capture group 1
/x # invoke free-spacing regex definition mode
[^`\r\n] contains \r (carriage return) in the event that the file was created with Windows. If desired, [^`]* can be replaced with .*? (match zero or more characters, as few as possible).