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jieyouxu merged 2 commits into from
Oct 10, 2026
Merged

Use indoc for multiline strings in tests #7169

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ac4369b
Use indoc for multiline strings in tests
joshka Oct 7, 2026
5c23798
Use panicdoc for multiline test diagnostics
joshka Oct 9, 2026
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16 changes: 16 additions & 0 deletions Cargo.lock
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1 change: 1 addition & 0 deletions Cargo.toml
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Expand Up @@ -61,6 +61,7 @@ rustfmt-config_proc_macro = { version = "0.3", path = "config_proc_macro" }
semver = "1.0.21"

[dev-dependencies]
indoc = "2.0.8"

@jieyouxu jieyouxu Oct 10, 2026 •
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@ytmimi a quick vibecheck on the extra dev-dependency: do you think the changes here pull its weight? I more-or-less neutral with a lean towards "seems nicer for these cases".

@joshka joshka Oct 10, 2026

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Yes—I think the places where indoc helps read a bit nicer, and I have more tests planned that would benefit similarly. I wrote a small dedent! macro as an alternative in that upcoming change (respecting the one LLM change in flight request to post this and the followups that sit on top of it), but that leaves rustfmt maintainers maintaining code that duplicates an established, stable solution.

My calculus is that indoc is a small crate—about 17 KB and 405 lines of code—with broad adoption. The readability benefit seems worth the dependency, especially as a dev-dependency.

Personally, I’d also be comfortable with it as a regular dependency, though I understand why a foundational tool like rustfmt would be more conservative. It feels like functionality that could reasonably belong in the standard library.

So I see little downside to using it for tests, and a relatively small tradeoff even for production code.

@jieyouxu jieyouxu Oct 10, 2026 •
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Hm yeah. Since this is dev-deps and test-only, I think it's fine introducing it.

Re. the calculus, indoc also has the other variants for UX that I don't think we want to be maintaining ourselves.

tempfile = "3.23.0"
insta = { version = "1.48.0", features = ["filters"] }

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6 changes: 5 additions & 1 deletion src/config/mod.rs
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Expand Up @@ -550,6 +550,7 @@ fn config_path(options: &dyn CliOptions) -> Result<Option<PathBuf>, Error> {
#[cfg(test)]
mod test {
use super::*;
use indoc::formatdoc;
use std::str;

use crate::config::macro_names::{MacroName, MacroSelectors};
Expand Down Expand Up @@ -726,7 +727,10 @@ mod test {
let toml = used_options.to_toml().unwrap();
assert_eq!(
toml,
format!("merge_derives = {merge_derives}\nskip_children = {skip_children}\n",)
formatdoc! {"
merge_derives = {merge_derives}
skip_children = {skip_children}
"}
);
}

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33 changes: 25 additions & 8 deletions src/emitter/checkstyle.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,7 @@ where
#[cfg(test)]
mod tests {
use super::*;
use indoc::indoc;
use std::path::PathBuf;

#[test]
Expand All @@ -89,11 +90,27 @@ mod tests {
#[test]
fn emits_single_xml_tree_containing_all_files() {
let bin_file = "src/bin.rs";
let bin_original = ["fn main() {", "println!(\"Hello, world!\");", "}"];
let bin_formatted = ["fn main() {", " println!(\"Hello, world!\");", "}"];
let bin_original = indoc! {r#"
fn main() {
println!("Hello, world!");
}
"#};
let bin_formatted = indoc! {r#"
fn main() {
println!("Hello, world!");
}
"#};
let lib_file = "src/lib.rs";
let lib_original = ["fn greet() {", "println!(\"Greetings!\");", "}"];
let lib_formatted = ["fn greet() {", " println!(\"Greetings!\");", "}"];
let lib_original = indoc! {r#"
fn greet() {
println!("Greetings!");
}
"#};
let lib_formatted = indoc! {r#"
fn greet() {
println!("Greetings!");
}
"#};
let mut writer = Vec::new();
let mut emitter = CheckstyleEmitter::default();
let _ = emitter.emit_header(&mut writer);
Expand All @@ -102,8 +119,8 @@ mod tests {
&mut writer,
FormattedFile {
filename: &FileName::Real(PathBuf::from(bin_file)),
original_text: &bin_original.join("\n"),
formatted_text: &bin_formatted.join("\n"),
original_text: bin_original,
formatted_text: bin_formatted,
},
)
.unwrap();
Expand All @@ -112,8 +129,8 @@ mod tests {
&mut writer,
FormattedFile {
filename: &FileName::Real(PathBuf::from(lib_file)),
original_text: &lib_original.join("\n"),
formatted_text: &lib_formatted.join("\n"),
original_text: lib_original,
formatted_text: lib_formatted,
},
)
.unwrap();
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30 changes: 25 additions & 5 deletions src/emitter/diff.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,7 @@ impl Emitter for DiffEmitter {
#[cfg(test)]
mod tests {
use super::*;
use indoc::{formatdoc, indoc};
use std::path::PathBuf;

#[test]
Expand All @@ -75,11 +76,27 @@ mod tests {
#[test]
fn prints_file_names_when_config_is_enabled() {
let bin_file = "src/bin.rs";
let bin_original = "fn main() {\nprintln!(\"Hello, world!\");\n}";
let bin_formatted = "fn main() {\n println!(\"Hello, world!\");\n}";
let bin_original = indoc! {r#"
fn main() {
println!("Hello, world!");
}
"#};
let bin_formatted = indoc! {r#"
fn main() {
println!("Hello, world!");
}
"#};
let lib_file = "src/lib.rs";
let lib_original = "fn greet() {\nprintln!(\"Greetings!\");\n}";
let lib_formatted = "fn greet() {\n println!(\"Greetings!\");\n}";
let lib_original = indoc! {r#"
fn greet() {
println!("Greetings!");
}
"#};
let lib_formatted = indoc! {r#"
fn greet() {
println!("Greetings!");
}
"#};

let mut writer = Vec::new();
let mut config = Config::default();
Expand Down Expand Up @@ -108,7 +125,10 @@ mod tests {

assert_eq!(
String::from_utf8(writer).unwrap(),
format!("{bin_file}\n{lib_file}\n"),
formatdoc! {"
{bin_file}
{lib_file}
"},
)
}

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105 changes: 65 additions & 40 deletions src/emitter/json.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -106,6 +106,7 @@ impl JsonEmitter {
#[cfg(test)]
mod tests {
use super::*;
use indoc::indoc;
use std::path::PathBuf;

#[test]
Expand All @@ -122,7 +123,12 @@ mod tests {
expected_begin_line: 79,
expected_end_line: 82,
original: String::from("fn Foo<T>() where T: Bar {\n"),
expected: String::from("fn Foo<T>()\nwhere\n T: Bar,\n{\n"),
expected: String::from(indoc! {"
fn Foo<T>()
where
T: Bar,
{
"}),
}],
};
let mismatch = Mismatch {
Expand Down Expand Up @@ -213,32 +219,32 @@ mod tests {
#[test]
fn emits_array_with_files_with_diffs() {
let file_name = "src/bin.rs";
let original = [
"fn main() {",
"println!(\"Hello, world!\");",
"}",
"",
"#[cfg(test)]",
"mod tests {",
"#[test]",
"fn it_works() {",
" assert_eq!(2 + 2, 4);",
"}",
"}",
];
let formatted = [
"fn main() {",
" println!(\"Hello, world!\");",
"}",
"",
"#[cfg(test)]",
"mod tests {",
" #[test]",
" fn it_works() {",
" assert_eq!(2 + 2, 4);",
" }",
"}",
];
let original = indoc! {r#"
fn main() {
println!("Hello, world!");
}

#[cfg(test)]
mod tests {
#[test]
fn it_works() {
assert_eq!(2 + 2, 4);
}
}
"#};
let formatted = indoc! {r#"
fn main() {
println!("Hello, world!");
}

#[cfg(test)]
mod tests {
#[test]
fn it_works() {
assert_eq!(2 + 2, 4);
}
}
"#};
let mut writer = Vec::new();
let mut emitter = JsonEmitter::default();
let _ = emitter.emit_header(&mut writer);
Expand All @@ -247,8 +253,8 @@ mod tests {
&mut writer,
FormattedFile {
filename: &FileName::Real(PathBuf::from(file_name)),
original_text: &original.join("\n"),
formatted_text: &formatted.join("\n"),
original_text: original,
formatted_text: formatted,
},
)
.unwrap();
Expand All @@ -269,9 +275,12 @@ mod tests {
original_end_line: 10,
expected_begin_line: 7,
expected_end_line: 10,
original: String::from(
"#[test]\nfn it_works() {\n assert_eq!(2 + 2, 4);\n}\n",
),
original: String::from(indoc! {"
#[test]
fn it_works() {
assert_eq!(2 + 2, 4);
}
"}),
expected: String::from(
" #[test]\n fn it_works() {\n assert_eq!(2 + 2, 4);\n }\n",
),
Expand All @@ -286,11 +295,27 @@ mod tests {
#[test]
fn emits_valid_json_with_multiple_files() {
let bin_file = "src/bin.rs";
let bin_original = ["fn main() {", "println!(\"Hello, world!\");", "}"];
let bin_formatted = ["fn main() {", " println!(\"Hello, world!\");", "}"];
let bin_original = indoc! {r#"
fn main() {
println!("Hello, world!");
}
"#};
let bin_formatted = indoc! {r#"
fn main() {
println!("Hello, world!");
}
"#};
let lib_file = "src/lib.rs";
let lib_original = ["fn greet() {", "println!(\"Greetings!\");", "}"];
let lib_formatted = ["fn greet() {", " println!(\"Greetings!\");", "}"];
let lib_original = indoc! {r#"
fn greet() {
println!("Greetings!");
}
"#};
let lib_formatted = indoc! {r#"
fn greet() {
println!("Greetings!");
}
"#};
let mut writer = Vec::new();
let mut emitter = JsonEmitter::default();
let _ = emitter.emit_header(&mut writer);
Expand All @@ -299,8 +324,8 @@ mod tests {
&mut writer,
FormattedFile {
filename: &FileName::Real(PathBuf::from(bin_file)),
original_text: &bin_original.join("\n"),
formatted_text: &bin_formatted.join("\n"),
original_text: bin_original,
formatted_text: bin_formatted,
},
)
.unwrap();
Expand All @@ -309,8 +334,8 @@ mod tests {
&mut writer,
FormattedFile {
filename: &FileName::Real(PathBuf::from(lib_file)),
original_text: &lib_original.join("\n"),
formatted_text: &lib_formatted.join("\n"),
original_text: lib_original,
formatted_text: lib_formatted,
},
)
.unwrap();
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9 changes: 8 additions & 1 deletion src/rustfmt_diff.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -284,6 +284,7 @@ mod test {
use super::DiffLine::*;
use super::{Mismatch, make_diff};
use super::{ModifiedChunk, ModifiedLines};
use indoc::indoc;

#[test]
fn diff_simple() {
Expand Down Expand Up @@ -370,7 +371,13 @@ mod test {
fn modified_lines_from_str() {
use std::str::FromStr;

let src = "1 6 2\nfn some() {}\nfn main() {}\n25 3 1\n struct Test {}";
let src = indoc! {"
1 6 2
fn some() {}
fn main() {}
25 3 1
struct Test {}
"};
let lines = ModifiedLines::from_str(src).unwrap();
assert_eq!(
lines,
Expand Down
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