WIP: Revert this commit and break into individual commits

Configurations.md

@@ -2692,6 +2692,20 @@ By default this option is set as a percentage of [`max_width`](#max_width) provi
 
 See also [`max_width`](#max_width) and [`use_small_heuristics`](#use_small_heuristics)
 
+## `style_edition`
+
+The style edition used to format your code. rustfmt output may differ between style editions.
+
+- **Default value**: `"2015"`
+- **Possible values**: `"2015"`, `"2018"`, `"2021"`, `"2024"`
+- **Stable**: Yes
+
+You can specify which style edition to use via the `--style-edition` CLI option or via your `rustfmt.toml`.
+
+```toml
+style_edition = "2021"
+```
+
 ## `tab_spaces`
 
 Number of spaces per tab

src/bin/main.rs

@@ -18,7 +18,7 @@ use std::str::FromStr;
 use getopts::{Matches, Options};
 
 use crate::rustfmt::{
-    load_config, CliOptions, Color, Config, Edition, EmitMode, FileLines, FileName,
+    load_config, CliOptions, Color, Config, Edition, StyleEdition, EmitMode, FileLines, FileName,
     FormatReportFormatterBuilder, Input, Session, Verbosity,
 };
 
@@ -130,6 +130,15 @@ fn make_opts() -> Options {
         "[Path for the configuration file]",
     );
     opts.optopt("", "edition", "Rust edition to use", "[2015|2018|2021]");
+    opts.optopt(
+        "",
+        "style-edition",
+        "Rustfmt style edition used to format your code. If specified, this style edition will \
+        take precedence over the value configured in any `rustfmt.toml`. rustfmt output may \
+        differ between style editions. If not specified, style-edition will be inferred from the \
+        configured `--edition`",
+        "[2015|2018|2021|2024]",
+    );
     opts.optopt(
         "",
         "color",
@@ -207,6 +216,8 @@ fn is_nightly() -> bool {
 fn execute(opts: &Options) -> Result<i32> {
     let matches = opts.parse(env::args().skip(1))?;
     let options = GetOptsOptions::from_matches(&matches)?;
+    let style_edition = options.style_edition;
+    let edition = options.edition;
 
     match determine_operation(&matches)? {
         Operation::Help(HelpOp::None) => {
@@ -244,7 +255,7 @@ fn execute(opts: &Options) -> Result<i32> {
             let file = PathBuf::from(path);
             let file = file.canonicalize().unwrap_or(file);
 
-            let (config, _) = load_config(Some(file.parent().unwrap()), Some(options))?;
+            let (config, _) = load_config(style_edition, edition, Some(file.parent().unwrap()), Some(options))?;
             let toml = config.all_options().to_toml()?;
             io::stdout().write_all(toml.as_bytes())?;
 
@@ -259,8 +270,11 @@ fn execute(opts: &Options) -> Result<i32> {
 }
 
 fn format_string(input: String, options: GetOptsOptions) -> Result<i32> {
+    let style_edition = options.style_edition;
+    let edition = options.edition;
+
     // try to read config from local directory
-    let (mut config, _) = load_config(Some(Path::new(".")), Some(options.clone()))?;
+    let (mut config, _) = load_config(style_edition, edition, Some(Path::new(".")), Some(options.clone()))?;
 
     if options.check {
         config.set().emit_mode(EmitMode::Diff);
@@ -306,7 +320,10 @@ fn format(
     options: &GetOptsOptions,
 ) -> Result<i32> {
     options.verify_file_lines(&files);
-    let (config, config_path) = load_config(None, Some(options.clone()))?;
+    let style_edition = options.style_edition;
+    let edition = options.edition;
+
+    let (config, config_path) = load_config(style_edition, edition, None, Some(options.clone()))?;
 
     if config.verbose() == Verbosity::Verbose {
         if let Some(path) = config_path.as_ref() {
@@ -328,7 +345,7 @@ fn format(
             // Check the file directory if the config-path could not be read or not provided
             if config_path.is_none() {
                 let (local_config, config_path) =
-                    load_config(Some(file.parent().unwrap()), Some(options.clone()))?;
+                    load_config(style_edition, edition, Some(file.parent().unwrap()), Some(options.clone()))?;
                 if local_config.verbose() == Verbosity::Verbose {
                     if let Some(path) = config_path {
                         println!(
@@ -514,6 +531,7 @@ struct GetOptsOptions {
     backup: bool,
     check: bool,
     edition: Option<Edition>,
+    style_edition: Option<StyleEdition>,
     color: Option<Color>,
     file_lines: FileLines, // Default is all lines in all files.
     unstable_features: bool,
@@ -605,6 +623,10 @@ impl GetOptsOptions {
             options.edition = Some(edition_from_edition_str(edition_str)?);
         }
 
+        if let Some(ref style_edition) = matches.opt_str("style-edition") {
+            options.style_edition = Some(style_edition_from_edition_str(style_edition)?);
+        }
+
         if matches.opt_present("backup") {
             options.backup = true;
         }
@@ -702,6 +724,16 @@ fn edition_from_edition_str(edition_str: &str) -> Result<Edition> {
     }
 }
 
+fn style_edition_from_edition_str(edition_str: &str) -> Result<StyleEdition> {
+    match edition_str {
+        "2015" => Ok(StyleEdition::Edition2015),
+        "2018" => Ok(StyleEdition::Edition2018),
+        "2021" => Ok(StyleEdition::Edition2021),
+        "2024" => Ok(StyleEdition::Edition2024),
+        _ => Err(format_err!("Invalid value for `--style-edition`")),
+    }
+}
+
 fn emit_mode_from_emit_str(emit_str: &str) -> Result<EmitMode> {
     match emit_str {
         "files" => Ok(EmitMode::Files),