Regex: Removing Space Between Quotes, And Stopping Before a Colon (With Yahoo Pipes)

I've been working on this for a while, but it's beyond my understanding of regex.

I'm using Yahoo Pipes on an RSS, and I want to create hashtags from titles; so, I'd like to remove space from everything between quotes, but, if there's a colon within the quotes, I only want the space removed between the words before the colon.

And, it would be great if I could also capture the unspaced words as a group, to be able to use: #$1 to output the hashtag in one step.

So, something like:

"The New Apple: Worlds Within Worlds" Before We Begin...

Could be substituted like #$1 - with this result:

"#TheNewApple: Worlds Within Worlds" Before We Begin...

After some work, I was able to come up with, this regex:

\s(?=\s)?|(‘|’|(Review)|:.*)

("Review" was a word that often came before colons and wouldn't be stripped, if it were later in the title; that's what that's for, but I would like to not require that, to be more universal)

But, it has two problems:

I have to use multiple steps. The result of that regex would be:
```
"TheNewApple: Worlds Within Worlds" Before We Begin...
```

And I could then add another regex step, to put the hash # in front

But, it only works if the quotes are first, and I don't know how to fix that...

Solution

You can do this all in one step with regex, with a caveat. You run into problems with a repeated capturing group because only the last iteration is available in the replacement string. Searching for ( (\w+))+ and replacing with $2 will replace all the words with just the last match - not what we want.

The way around this is to repeat the pattern an arbitrary number of times that will suffice for your use. Each separate group can be referenced.

Search: "(\w+)(?: (\w+))?(?: (\w+))?(?: (\w+))?(?: (\w+))?(?: (\w+))?

Replace: "#$1$2$3$4$5$6

This will replace up to 6-word titles, exactly as you need them. First, "(\w+) matches any word following a quote. In the replacement string, it is put back as "#$1, adding the hashtag. The rest is a repeated list of (?: (\w+))? matches, each matching a possible space and word. Notice the space is part of a non-capturing group; only the word is part of the inner capture group. In the replacement string, I have $1$2$3$4$5$6, which puts back the words, without the spaces. Notice that a colon will not match any part of this, so it will stop once it hits a colon.

Examples:

"The New Apple: Worlds Within Worlds" Before We Begin...
"The New Apple" Before We Begin...
"One: Two"
only "One" word
this has "Two Words"
"The Great Big Apple Dumpling"
"The Great Big Apple Dumpling Again: Part 2"

Results:

"#TheNewApple: Worlds Within Worlds" Before We Begin...
"#TheNewApple" Before We Begin...
"#One: Two"
only "#One" word
this has "#TwoWords"
"#TheGreatBigAppleDumpling"
"#TheGreatBigAppleDumplingAgain: Part 2"