test(language_server): add Tester for ServerFormatter

crates/oxc_language_server/fixtures/formatter/basic/basic.ts

@@ -0,0 +1,33 @@
+class C1 {
+    #name: string;
+
+    public get name() {
+        return this.#name;
+    }
+
+    private set name(name: string) {
+        this.#name = name;
+    }
+}
+
+class C2 {
+    #name: string;
+
+    private set name(name: string) {
+        this.#name = name;
+    }
+
+    public get name() {
+        return this.#name;
+    }
+}
+
+const c1 = new C1();
+const c2 = new C2();
+
+
+// no error
+c1.name;
+
+// no error
+c2.name;

crates/oxc_language_server/src/formatter/mod.rs

@@ -1,2 +1,4 @@
 pub mod options;
 pub mod server_formatter;
+#[cfg(test)]
+mod tester;

crates/oxc_language_server/src/formatter/server_formatter.rs

@@ -107,6 +107,7 @@ fn compute_minimal_text_edit<'a>(
 #[cfg(test)]
 mod tests {
     use super::compute_minimal_text_edit;
+    use crate::formatter::{options::FormatOptions, tester::Tester};
 
     #[test]
     #[should_panic(expected = "assertion failed")]
@@ -188,4 +189,10 @@ mod tests {
         let (start, end, replacement) = compute_minimal_text_edit(&src, &formatted);
         assert_eq!((start, end, replacement), (0, 0, "b"));
     }
+
+    #[test]
+    fn test_formatter() {
+        Tester::new("fixtures/formatter/basic", Some(FormatOptions { experimental: true }))
+            .format_and_snapshot_single_file("basic.ts");
+    }
 }

crates/oxc_language_server/src/formatter/tester.rs

@@ -0,0 +1,91 @@
+use std::{fmt::Write, path::PathBuf};
+
+use tower_lsp_server::{
+    UriExt,
+    lsp_types::{TextEdit, Uri},
+};
+
+use crate::{formatter::options::FormatOptions, options::Options, worker::WorkspaceWorker};
+
+/// Given a file path relative to the crate root directory, return the absolute path of the file.
+pub fn get_file_path(relative_file_path: &str) -> PathBuf {
+    std::env::current_dir().expect("could not get current dir").join(relative_file_path)
+}
+
+/// Given a file path relative to the crate root directory, return the URI of the file.
+pub fn get_file_uri(relative_file_path: &str) -> Uri {
+    Uri::from_file_path(get_file_path(relative_file_path))
+        .expect("failed to convert file path to URL")
+}
+
+fn get_snapshot_from_text_edits(edits: &[TextEdit]) -> String {
+    edits
+        .iter()
+        .map(|edit| format!("{:#?},\n\n{:?}", edit.range, edit.new_text))
+        .collect::<Vec<_>>()
+        .join("\n")
+}
+
+/// Testing struct for the [formatter server][crate::formatter::server_formatter::ServerFormatter].
+pub struct Tester<'t> {
+    relative_root_dir: &'t str,
+    options: Option<FormatOptions>,
+}
+
+impl Tester<'_> {
+    pub fn new(relative_root_dir: &'static str, options: Option<FormatOptions>) -> Self {
+        Self { relative_root_dir, options }
+    }
+
+    async fn create_workspace_worker(&self) -> WorkspaceWorker {
+        let absolute_path = std::env::current_dir()
+            .expect("could not get current dir")
+            .join(self.relative_root_dir);
+        let uri = Uri::from_file_path(absolute_path).expect("could not convert current dir to uri");
+        let worker = WorkspaceWorker::new(uri);
+        let option =
+            &Options { format: self.options.clone().unwrap_or_default(), ..Default::default() };
+        worker.start_worker(option).await;
+
+        worker
+    }
+
+    pub fn format_and_snapshot_single_file(&self, relative_file_path: &str) {
+        self.format_and_snapshot_multiple_file(&[relative_file_path]);
+    }
+
+    #[expect(clippy::disallowed_methods)]
+    pub fn format_and_snapshot_multiple_file(&self, relative_file_paths: &[&str]) {
+        let mut snapshot_result = String::new();
+        for relative_file_path in relative_file_paths {
+            let uri = get_file_uri(&format!("{}/{}", self.relative_root_dir, relative_file_path));
+            let formatted = tokio::runtime::Runtime::new().unwrap().block_on(async {
+                self.create_workspace_worker().await.format_file(&uri, None).await
+            });
+
+            let snapshot = if let Some(formatted) = formatted {
+                get_snapshot_from_text_edits(&formatted)
+            } else {
+                "File is ignored".to_string()
+            };
+
+            let _ = write!(
+                snapshot_result,
+                "########## \nfile: {}/{relative_file_path}\n----------\n{snapshot}\n",
+                self.relative_root_dir
+            );
+        }
+
+        let snapshot_name = self.relative_root_dir.replace('/', "_");
+        let mut settings = insta::Settings::clone_current();
+        settings.set_snapshot_path(
+            std::env::current_dir().expect("could not get current dir").join("src/snapshots"),
+        );
+        settings.set_prepend_module_to_snapshot(false);
+        settings.set_omit_expression(true);
+        settings.set_snapshot_suffix(relative_file_paths.join("_").replace('\\', "/"));
+        settings.bind(|| {
+            insta::assert_snapshot!(snapshot_name, snapshot_result);
+        });
+    }
+}

crates/oxc_language_server/src/snapshots/fixtures_formatter_basic@basic.ts.snap

@@ -0,0 +1,18 @@
+---
+source: crates/oxc_language_server/src/formatter/tester.rs
+---
+########## 
+file: fixtures/formatter/basic/basic.ts
+----------
+Range {
+    start: Position {
+        line: 1,
+        character: 2,
+    },
+    end: Position {
+        line: 26,
+        character: 0,
+    },
+},
+
+"#name: string;\n\n  public get name() {\n    return this.#name;\n  }\n\n  private set name(name: string) {\n    this.#name = name;\n  }\n}\n\nclass C2 {\n  #name: string;\n\n  private set name(name: string) {\n    this.#name = name;\n  }\n\n  public get name() {\n    return this.#name;\n  }\n}\n\nconst c1 = new C1();\nconst c2 = new C2();"