Hi Thad! "Il faut cultiver notre jardin." [https://againstprofphil.org/2017/02/20/il-faut-cultiver-notre-jardin/]

I did add a contracted form to a lexeme few weeks ago, just to test the water. (https://www.wikidata.org/w/index.php?title=Lexeme:L1883&diff=1248168703.) Specifically, this was "'m" as a contraction of "am" and, therefore, a form of be. But, as is common with contractions, the form is permitted only in specific contexts (some languages, like French, require contractions in particular contexts, so we certainly can't ignore them). 

1. I'm not convinced that "we'll" is a phrase. It is certainly a contraction (of either "we shall" or "we will"). My understanding is that a lexical phrase would only be admitted as a lexeme if its definition (including its inflection) is not fully implied by its constituents. And I suggest that is not the case here. Rather, it is justified as a lexeme by the fact that it is a contraction (personally, I don't entirely agree with this justification in this particular case, because "'ll" is practically a separate word in contemporary English, but perhaps that 'll be a topic for another day).

2. From 1, "we'll" has three forms: "we'll", "we shall" and "we will". But these are not inflections, so perhaps they aren't strictly forms at all. Semantics aside, "we'll" is neither more nor less than "we" followed by "'ll", with the orthographic convention of no intervening space where a word begins with an apostrophe (unless 'tis an exception). Anyway...
What sort of function did you have in mind? My theory would be that only a parsing function would start with "we'll" and its result is ambiguous because "'ll" is ambiguous (being a form in two separate lexemes, shall and will).
Since you mention searching, I'd guess that a search would want to find results containing any one of the three forms, given "we'll", but only the given form and "we'll", given either of the other forms.
Since you also mention "equivalency", I would say that there is equivalence between "we'll" and "we shall", and there is equivalence between "we'll" and "we will", but there is no (implied) equivalence between "we shall" and "we will". (For a clearer case, consider "we'd", which might mean "we had" or "we should" or "we would". You might suspect equivalence between "we should" and "we would" but not between either and "we had". So it is not the common form of the contraction that implies the suspected equivalence, it is the fading/faded distinction between shall and will, facilitated by common contractions.)
Since you mention renderers, I would say not. But that's not a definitive no. It's more a case of we'll build that bridge when we get to where it isn't ;) A rendering function should be expected to leave the matter of contraction 'til later (which, like tomorrow, never comes). According to this theory, there might come a time when a renderer function has (in effect) "we shall" and returns "we'll", but not the other way around. (And according to my principle of losslessness, the result is actually both: "we'll<!--optional contraction of: we shall-->", in essence.)

3. No idea! (Just saying...)

Just to backtrack to your use case, I'd be inclined to lemmatize the entire phrase. My millennial Collins English Dictionary has sense 32 for cross: "cross a bridge when one comes to it". My Oxford Dictionary of English has the phrase "cross that bridge when one comes to it" under bridge. One never says "one", of course! There seem to be five or six occurrences in the British National Corpus. Five say "cross that bridge when"; three are for "we" (one attributive modifying "attitude", one imperative: "let's cross that bridge when we *get* to it, one: "we can cross..."), one each for "he" and "she" "would" (in the same text but not close together), and one, well... "we cross our bridges when we come to them and burn them behind us..." (Why, thank you, Sir Tom! https://en.wikipedia.org/wiki/Tom_Stoppard)

Thank you for "listening",

On Saturday, 29 August 2020, Thad Guidry <thadguidry@gmail.com> wrote:
Hi Team,

As usual for me, I love digging and pulling out weeds from the garden beds on the weekend. :-)

I searched the repo and did not see "apostrophe" or "contraction" mentioned at all.

I was hoping to see an example conversion function to help with contractions (shortened forms of words where letters have been omitted and replaced by apostrophes and sometimes other characters) ?

My use case (in the future) is to help Abstract Wikipedia to more easily handle search & matching for English idioms and deal with alternative variants that sometimes have contracted forms of words within them.  For example:
"We will cross that bridge when we come to it"
"We'll cross that bridge when we come to it"

Idioms are so complex in English and many alternative variants with optional hyphens, apostrophes, etc.
So I'm (<-- a contraction!) trying to understand some of the future ideas on how searchability might be improved by allowing hints somehow in Wikidata Lexemes and what a first practice (maybe not best practice yet!) would begin to look like.

We might have parsing functions that already know that "we will" = "we'll".  The lexeme for "we'll" is in fact already there https://www.wikidata.org/wiki/Lexeme:L269709  GREAT!
But I think that lexeme and others are missing additional information to make them really useful with our later conversion functions or renderers?

So... Some of these questions are deep, forward thinking, and probably will not have the best answers right now, but it's (<--another contraction!!) useful to ask them now I think:
1.  Perhaps somehow mentioning that  https://www.wikidata.org/wiki/Lexeme:L269709 is a contraction and not only a phrase?  But I don't see how to do that currently.  Lexical category allows only 1.   If you know, let me know.
2. How would a function determine equivalency handled with Z-objects in the case of contractions?  For example, would the mere fact that on L269709 that there are 2 forms -F1 and -F2, automatically return a boolean True on some function?  Is that best?
3. Seeing as how ubiquitous contractions are... does that make them a good candidate in the future for separate indexing?
a. Is L269709 and its -F1 and -F2 forms good enough for further building very fast lookup or conversion functions for contractions that would use ElasticSearch indexes?  This could be performant enough and completely stored in memory for English language, I guess?

I'm all ears (<-- an idiom!!)(means I am listening)