Error in apply_guides(target, tar.capt, guide_fun) for `data.table`

[zhizhongpu]

Bug

random error that is uninformative

> mwe <- data.table::fread('mwe.csv')
> diffobj::diffPrint(target = mwe, current = mwe)
Error in apply_guides(target, tar.capt, guide_fun) : 
  `guides*` method must produce an integer vector containing unique index values for the `obj.as.chr` vector; If you did not specify a `guides` function or define custom `guides*` methods contact maintainer (see `?guides`).  Proceeding without guides.

similar to #111

Input data

mwe.csv

Variations

• droping any row solves the issue
• dropping any column solves the issue
• renaming any column to any of "a", "b", "c", "d" solves the issue
• not having the input data in data.table format solves the issue

Desire output

either make this more informative, or make the diff function output the expected diff (which is none in this case)

sessionInfo()

> sessionInfo()
R version 4.5.1 (2025-06-13)
Platform: aarch64-apple-darwin20
Running under: macOS Sequoia 15.7.3

Matrix products: default
BLAS:   /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib 
LAPACK: /Library/Frameworks/R.framework/Versions/4.5-arm64/Resources/lib/libRlapack.dylib;  LAPACK version 3.12.1

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     

loaded via a namespace (and not attached):
[1] compiler_4.5.1      later_1.4.5         tools_4.5.1        
[4] rstudioapi_0.18.0   crayon_1.5.3        Rcpp_1.1.1         
[7] diffobj_0.3.6       data.table_1.18.2.1 rsthemes_0.5.0