When evaluating a braced paste() expression that returns a single string, glue() incorporates text outside the braces

[homerhanumat]

This

library(glue)
vowels <- c("a", "e", "i", "o", "u")
glue("The vowels are: {paste(vowels, collapse = ", ")}.")

produces:

The vowels are: a.
The vowels are: e.
The vowels are: i.
The vowels are: o.
The vowels are: u.

One expects the output to be the same as:

library(glue)
vowels <- c("a", "e", "i", "o", "u")
vowels_pasted <- paste(vowels, collapse = ", ")
glue("The vowels are: {vowels_pasted}.")

The vowels are: a, e, i, o, u.

Session info:

R version 4.4.2 (2024-10-31)
Platform: aarch64-apple-darwin20
Running under: macOS Sequoia 15.1.1

Matrix products: default
BLAS:   /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib 
LAPACK: /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/lib/libRlapack.dylib;  LAPACK version 3.12.0

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

time zone: America/New_York
tzcode source: internal

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] glue_1.8.0

loaded via a namespace (and not attached):
[1] compiler_4.4.2    cli_3.6.3         tools_4.4.2       rstudioapi_0.17.0
[5] crayon_1.5.3      rlang_1.1.4     

[remlapmot]

I'd guess this is simply because you've used double quotes twice.

Switching one of the double quotes to single quotes gives the expected output.

library(glue)
vowels <- c("a", "e", "i", "o", "u")
glue("The vowels are: {paste(vowels, collapse = ', ')}.")
#> The vowels are: a, e, i, o, u.

^{Created on 2024-12-09 with reprex v2.1.1}

[homerhanumat]

That's right.