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One cool thing that happens if you work resonates in the community is that you see other people using it. In this blog post I am going to address a typical question people have when they want to use a source code formatter – in particular styler:

I don’t like rule xyz of the tidyverse style guide, which is the default style guide implemented in styler. How can I tell styler not to apply it?

Theory

First, I think reading the docs would be a good approach. There are two resources:

• The help file for the function tidyverse_style(), which returns the transformer functions that prettify your code. It has a few interesting arguments, some of which are rather complex.¹
• If you can’t get styler behaving the way you want using the arguments of tidyverse_style(), you have another option, which is described in a vignette: Creating your own style guide. Yes, I admit, it’s pretty long and if you don’t want to become a styler expert, it may be a little bit overwhelming.

If you don’t care about how to create new rules but you simply want to remove a rule, I have good news for you: There is a quick way to do it. These are the steps you need to complete in order to do it:

• Figure out which transformer function in the transformers returned by tidyerse_style() corresponds to the rule you want to remove.
• Set that element in the list to NULL, which is equivalent to removing it.
• Pass the list to style_text as a transformer.

Practice

Lets assume you want to remove the rule that turns = into <- for assignment. That means you want string = "hi there"

to remain unchanged after applying styler. This is not the case if you use the default style guide of styler:

library(styler)
style_text("string = 'hi there'")

string <- "hi there"

So you need to figure out which rule is responsible for this. Let’s check the transformer categories used with the tidyverse style guide.

transformers <- tidyverse_style()
names(transformers)

## [1] "initialize"        "line_break"        "space"            
## [4] "token"             "indention"         "use_raw_indention"
## [7] "reindention"

From the aforementioned vignette:

We note that there are different types of transformer functions. initialize initializes some variables in the nested parse table (so it is not actually a transformer), and the other elements modify either spacing, line breaks or tokens. use_raw_indention is not a function, it is just an option.

Now, we can look at the names of the rules that are sub-elements of the transformer categories.

library(styler)
purrr::modify_depth(transformers, 1, names)

## $initialize
## [1] "initialize"
## 
## $line_break
## [1] "remove_line_break_before_curly_opening"            
## [2] "remove_line_break_before_round_closing_after_curly"
## [3] "remove_line_break_before_round_closing_fun_dec"    
## [4] "style_line_break_around_curly"                     
## [5] "set_line_break_after_opening_if_call_is_multi_line"
## [6] "set_line_break_before_closing_call"                
## [7] "remove_line_break_in_empty_fun_call"               
## [8] "add_line_break_after_pipe"                         
## 
## $space
##  [1] "indent_braces"                     
##  [2] "unindent_fun_dec"                  
##  [3] "indent_op"                         
##  [4] "indent_eq_sub"                     
##  [5] "indent_without_paren"              
##  [6] "fix_quotes"                        
##  [7] "remove_space_before_closing_paren" 
##  [8] "remove_space_before_opening_paren" 
##  [9] "add_space_after_for_if_while"      
## [10] "add_space_before_brace"            
## [11] "remove_space_before_comma"         
## [12] "style_space_around_math_token"     
## [13] "style_space_around_tilde"          
## [14] "spacing_around_op"                 
## [15] "spacing_around_comma"              
## [16] "remove_space_after_opening_paren"  
## [17] "remove_space_after_excl"           
## [18] "set_space_after_bang_bang"         
## [19] "remove_space_before_dollar"        
## [20] "remove_space_after_fun_dec"        
## [21] "remove_space_around_colons"        
## [22] "start_comments_with_space"         
## [23] "remove_space_after_unary_pm_nested"
## [24] "spacing_before_comments"           
## [25] "set_space_between_levels"          
## [26] "set_space_between_eq_sub_and_comma"
## 
## $token
## [1] "force_assignment_op"                   
## [2] "resolve_semicolon"                     
## [3] "add_brackets_in_pipe"                  
## [4] "remove_terminal_token_before_and_after"
## [5] "wrap_if_else_multi_line_in_curly"      
## 
## $indention
## [1] "update_indention_ref_fun_dec"
## 
## $use_raw_indention
## NULL
## 
## $reindention
## [1] "indention"     "comments_only"

Spotted the rule we want to get rid of? It’s under token and it’s called force_assignment_op. I agree, we could have chosen a better name. If you are not sure if you can guess from the name of the rule what it does you can also have a look at the function declaration of this (unexported) function.

styler:::force_assignment_op

## function (pd) 
## {
##     to_replace <- pd$token == "EQ_ASSIGN"
##     pd$token[to_replace] <- "LEFT_ASSIGN"
##     pd$text[to_replace] <- "<-"
##     pd
## }
## <bytecode: 0x3e00828>
## <environment: namespace:styler>

Next, you simply set that element to NULL.

transformers$token$force_assignment_op <- NULL

And you can use the modified transformer list as input to style_text()

style_text("string = 'hi there'", transformers = transformers)

string = "hi there"

That’s it. Note that the transformer functions and how they are returned by tidyverse_style() is not part of the exposed API. This means that the order, the naming etc. may change. For example, I only recently spotted that the rule to remove quotes (fix_quotes)is in the category space, which is clearly wrong and I think I will move it over to token in a future release of styler.

Some other rules and their tranformers

• You don’t like multi-line ifelse statements getting wrapped around curly braces: transformers$token$wrap_if_else_multi_line_in_curly.
• You don’t like mutli-line calls to be broken before the first named argument: transformers$line_break$set_line_break_after_opening_if_call_is_multi_line (interacting with transformers$line_break$set_line_break_before_closing_call).
• You don’t like the line being broken after the pipe: transformers$line_break$add_line_break_after_pipe
• You don’t like single quotes to be replaced by double quotes: transformers$space$fix_quotes.
• You don’t like comments to start with one space: transformers$space$start_comments_with_space

I think you get the idea. I nevertheless recommend using the tidyverse style guide as is since

• it is a well-established, thought-through style.
• using a consistent style (no matter which) reduces fraction in the community.

In case you want to add a custom rule, the vignette Customizing styler is still the way to go. If you have questions, don’t hesitate to post on Stackoverflow or leave a comment below.