replaceRE not working for me [SOLVED]

I’m trying to use replaceRE from the docs:

{{ "" | replaceRE "^https?://([^/]+).*" "$1" }} → “”

So source string, pipe symbol, replaceRE, match pattern, and replacement.

In my theme, I use replaceRE like this:

{{ .Plain | replaceRE "(\bReferences:.*$)" "wordNotInTextNatively" }}

According to an online validator, my regex matches all text from the Reference: heading till the end the of the string (which is what I want).

However, Hugo doesn’t do anything: there’s no error message, nor is the regex matched string removed from the .Plain output.

What am I missing? Thanks!

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If I don’t use word boundaries, replaceRE works for me. I’m not sure if it should do that?

If I run the following through an validator, they all match my word ‘References:’ and the remainder of the string:

  • \bReferences: \b.*$
  • \bReferences:.*$

But these don’t do something in Hugo. Instead, I need to use:

  • References: .*$
  • References:.*$ (or References:.* simplified).

Please let me know if I misunderstood replaceRE (then I need to do some more studying).

replaceRE works odd from my standpoint:

{{ .Plain | replaceRE "References:.*" "" }}
–> only replaces the word ‘References:’ but not any of the characters following that (despite .*).

{{ "copy paste of the article content here" | replaceRE "References:.*" "" }}
–> replaces the word ‘References:’ and anything after that till the end of the string.

From my understanding, replaceRE doesn’t behave consistently. (Or perhaps by design?)

Hugo uses the Go regular expression package which uses the re2 syntax. This is not pcre or javascript, so whatever syntax validator you’re using online may have some differences.

I suspect your problem is that you are trying to match a multi-line input string and need to turn on the multi-line flag with (?m). See this Go playground for an example of using the flag and what’s happening inside of Hugo.


Thanks @moorereason for the clarification and additional information. I didn’t realise that Hugo used a specific regex for this.

I’m a bit closer to the solution but not fully there yet. With an online regex tester for Go I verified that both (?m)(\bReferences:.*$) and (\bReferences:.*$) are valid regex matches for my content.

This doesn’t work for me however yet:

{{ .Plain | htmlEscape | replaceRE "(?m)(\bReferences:.*$)" ""}}

To see why, I used the Go playground example and set the input variable to output of .Plain | htmlEscape. And there it works; ‘References:’ and everything that follows after that word is replaced by ‘wordNotInTextNatively’.

But in Hugo, it doesn’t work; no error and the text from ‘References:’ onward is not replaced.

I’m using:

PS I:\site> hugo env
Hugo Static Site Generator v0.18.1 BuildDate: 2016-12-30T10:03:28+01:00

You need to escape the backslash in your pattern:

{{ .Content | replaceRE "(?m)(\\bReferences:.*$)" "" }}

Thanks @moorereason! With that, and your comment on Github saying that “the Go . pattern doesn’t match newlines. You have to pass the s flag to the group.” I completed my regex. :smile:

{{ .Plain | htmlEscape | replaceRE "(?m)(?s:\\bReferences:.*$)" "" }}

Thanks again for your help; without guidance I wouldn’t have come up with this in a year.

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