tidyr quasiquotation with lexical scoping

Question

I realize that tidy evaluation does not use lexical scoping, but I want the quasiquotation in rlang to look for symbols in the environment I decide.

Current behavior:

envir <- new.env(parent = globalenv())
eval(parse(text = "little_b <- 'b'"), envir = envir)
eval(rlang::expr(!!little_b), envir = envir)

## Error in (function (x)  : object 'little_b' not found

Instead, I want the last line to return "b". Bonus points if you find a version of eval() that does the job here AND works like evaluate::try_capture_stack().

FYI: I am trying to solve this issue.

tidyeval is all about lexical scoping ;) – Lionel Henry Jan 30 '18 at 12:11 — Lionel Henry, Jan 30 '18 at 12:11

akrun · Accepted Answer · 2018-01-30T12:19:12.027

2

We can use with to pass the expression within an environment

with(envir, expr(!!little_b))
#[1] "b"

Or another option is local

local(rlang::expr(!!little_b), envir = envir)
#[1] "b"

Or pass via quote in eval (as @lionel mentioned)

eval(quote(expr = rlang::expr(!! little_b)), envir = envir)
#[1] "b"

edited Jan 30 '18 at 12:19

answered Jan 30 '18 at 08:39

akrun

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The last example should be `quote()` instead of `substitute()` since you're not doing any substitution. – Lionel Henry Jan 30 '18 at 12:12

tidyr quasiquotation with lexical scoping

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