From 465046279325b09bb8ab76c0f111b34dfe498591 Mon Sep 17 00:00:00 2001 From: Akshay Date: Wed, 1 Apr 2020 11:58:30 +0530 Subject: new post: Rapid Refactoring With Vim --- posts/rapid_refactoring_with_vim.md | 198 ++++++++++++++++++++++++++++++++++++ 1 file changed, 198 insertions(+) create mode 100644 posts/rapid_refactoring_with_vim.md (limited to 'posts') diff --git a/posts/rapid_refactoring_with_vim.md b/posts/rapid_refactoring_with_vim.md new file mode 100644 index 0000000..66ca0e3 --- /dev/null +++ b/posts/rapid_refactoring_with_vim.md @@ -0,0 +1,198 @@ +Last weekend, I was tasked with refactoring the 96 unit +tests on +[ruma-events](https://github.com/ruma/ruma-events/pull/70) +to use strictly typed json objects using `serde_json::json!` +instead of raw strings. It was rather painless thanks to +vim :) + +Here's a small sample of what had to be done (note the lines +prefixed with the arrow): + +``` +→ use serde_json::{from_str}; + + #[test] + fn deserialize() { + assert_eq!( +→ from_str::(r#"{"set_tweak": "highlight"}"#), + Action::SetTweak(Tweak::Highlight { value: true }) + ); + } +``` + +had to be converted to: + +``` +→ use serde_json::{from_value}; + + #[test] + fn deserialize() { + assert_eq!( +→ from_value::(json!({"set_tweak": "highlight"})), + Action::SetTweak(Tweak::Highlight { value: true }) + ); + } +``` + +## The arglist + +For the initial pass, I decided to handle imports, this was +a simple find and replace operation, done to all the files +containing tests. Luckily, modules (and therefore files) +containing tests in Rust are annotated with the +`#[cfg(test)]` attribute. I opened all such files: + +``` +# `grep -l pattern files` lists all the files +# matching the pattern + +vim $(grep -l 'cfg\(test\)' ./**/*.rs) + +# expands to something like: +vim push_rules.rs room/member.rs key/verification/lib.rs +``` + +Starting vim with more than one file at the shell prompt +populates the arglist. Hit `:args` to see the list of +files currently ready to edit. The square [brackets] +indicate the current file. Navigate through the arglist +with `:next` and `:prev`. I use tpope's vim-unimpaired +[^un], which adds `]a` and `[a`, mapped to `:next` and +`:prev`. + +[^un]: https://github.com/tpope/vim-unimpaired + It also handles various other mappings, `]q` and `[q` to + navigate the quickfix list for example + +All that's left to do is the find and replace, for which we +will be using vim's `argdo`, applying a substitution to +every file in the arglist: + +``` +:argdo s/from_str/from_value/g +``` + +## The quickfix list + +Next up, replacing `r#" ... "#` with `json!( ... )`. I +couldn't search and replace that trivially, so I went with a +macro call [^macro] instead, starting with the cursor on +'r', represented by the caret, in my attempt to breakdown +the process: + +[^macro]: `:help recording` + +``` +BUFFER: r#" ... "#; + ^ + +ACTION: vllsjson!( + +BUFFER json!( ... "#; + ^ + +ACTION: $F# + +BUFFER: json!( ... "#; + ^ + +ACTION: vhs) + +BUFFER: json!( ... ); +``` + +Here's the recorded [^rec] macro in all its glory: +`vllsjson!($F#vhs)`. + +[^rec]: When I'm recording a macro, I prefer starting out by + storing it in register `q`, and then copying it over to + another register if it works as intended. I think of `qq` as + 'quick record'. + +Great! So now we just go ahead, find every occurrence of +`r#` and apply the macro right? Unfortunately, there were +more than a few occurrences of raw strings that had to stay +raw strings. Enter, the quickfix list. + +The idea behind the quickfix list is to jump from one +position in a file to another (maybe in a different file), +much like how the arglist lets you jump from one file to +another. + +One of the easiest ways to populate this list with a bunch +of positions is to use `vimgrep`: + +``` +# basic usage +:vimgrep pattern files + +# search for raw strings +:vimgrep 'r#' ./**/*.rs +``` + +Like `:next` and `:prev`, you can navigate the quickfix list +with `:cnext` and `:cprev`. Every time you move up or down +the list, vim indicates your index: + +``` +(1 of 131): r#"{"set_tweak": "highlight"}"#; +``` + +And just like `argdo`, you can `cdo` to apply commands to +*every* match in the quickfix list: + +``` +:cdo norm! @q +``` + +But, I had to manually pick out matches, and it involved +some button mashing. + +## External Filtering + +Some code reviews later, I was asked to format all the json +inside the `json!` macro. All you have to do is pass a +visual selection through a pretty json printer. Select the +range to be formatted in visual mode, and hit `:`, you will +notice the command line displaying what seems to be +gibberish: + +``` +:'<,'> +``` + +`'<` and `'>` are *marks* [^mark-motions]. More +specifically, they are marks that vim sets automatically +every time you make a visual selection, denoting the start +and end of the selection. + +[^mark-motions]: `:help mark-motions` + +A range is one or more line specifiers separated by a `,`: + +``` +:1,7 lines 1 through 7 +:32 just line 32 +:. the current line +:.,$ the current line to the last line +:'a,'b mark 'a' to mark 'b' +``` + +Most `:` commands can be prefixed by ranges. `:help +usr_10.txt` for more on that. + +Alright, lets pass json through `python -m json.tool`, a +json formatter that accepts `stdin` (note the use of `!` to +make use of an external program): + +``` +:'<,'>!python -m json.tool +``` + +Unfortunately that didn't quite work for me because the +range included some non-json text as well, a mix of regex +and macros helped fix that. I think you get the drift. + +Another fun filter I use from time to time is `:!sort`, to +sort css attributes, or `:!uniq` to remove repeated imports. + -- cgit v1.2.3