diff --git a/xtask/src/codegen.rs b/xtask/src/codegen.rs
index 78a84f68d0..98acd7fa67 100644
--- a/xtask/src/codegen.rs
+++ b/xtask/src/codegen.rs
@@ -15,7 +15,11 @@ use std::{
     path::{Path, PathBuf},
 };
 
-use crate::{not_bash::fs2, project_root, Result};
+use crate::{
+    ensure_rustfmt,
+    not_bash::{fs2, pushenv, run},
+    project_root, Result,
+};
 
 pub use self::{
     gen_assists_docs::{generate_assists_docs, generate_assists_tests},
@@ -62,6 +66,18 @@ fn update(path: &Path, contents: &str, mode: Mode) -> Result<()> {
     }
 }
 
+const PREAMBLE: &str = "Generated file, do not edit by hand, see `xtask/src/codegen`";
+
+fn reformat(text: impl std::fmt::Display) -> Result<String> {
+    let _e = pushenv("RUSTUP_TOOLCHAIN", "stable");
+    ensure_rustfmt()?;
+    let stdout = run!(
+        "rustfmt --config-path {} --config fn_single_line=true", project_root().join("rustfmt.toml").display();
+        <text.to_string().as_bytes()
+    )?;
+    Ok(format!("//! {}\n\n{}\n", PREAMBLE, stdout))
+}
+
 fn extract_comment_blocks(text: &str) -> Vec<Vec<String>> {
     do_extract_comment_blocks(text, false).into_iter().map(|(_line, block)| block).collect()
 }
diff --git a/xtask/src/codegen/gen_assists_docs.rs b/xtask/src/codegen/gen_assists_docs.rs
index 526941f73a..4f49685944 100644
--- a/xtask/src/codegen/gen_assists_docs.rs
+++ b/xtask/src/codegen/gen_assists_docs.rs
@@ -3,7 +3,7 @@
 use std::{fmt, fs, path::Path};
 
 use crate::{
-    codegen::{self, extract_comment_blocks_with_empty_lines, Location, Mode},
+    codegen::{self, extract_comment_blocks_with_empty_lines, reformat, Location, Mode, PREAMBLE},
     project_root, rust_files, Result,
 };
 
@@ -15,7 +15,7 @@ pub fn generate_assists_tests(mode: Mode) -> Result<()> {
 pub fn generate_assists_docs(mode: Mode) -> Result<()> {
     let assists = Assist::collect()?;
     let contents = assists.into_iter().map(|it| it.to_string()).collect::<Vec<_>>().join("\n\n");
-    let contents = contents.trim().to_string() + "\n";
+    let contents = format!("//{}\n{}\n", PREAMBLE, contents.trim());
     let dst = project_root().join("docs/user/generated_assists.adoc");
     codegen::update(&dst, &contents, mode)
 }
@@ -134,7 +134,7 @@ r#####"
 
         buf.push_str(&test)
     }
-    let buf = crate::reformat(buf)?;
+    let buf = reformat(buf)?;
     codegen::update(&project_root().join(codegen::ASSISTS_TESTS), &buf, mode)
 }
 
diff --git a/xtask/src/codegen/gen_feature_docs.rs b/xtask/src/codegen/gen_feature_docs.rs
index 31bc3839d0..3f0013e82a 100644
--- a/xtask/src/codegen/gen_feature_docs.rs
+++ b/xtask/src/codegen/gen_feature_docs.rs
@@ -3,14 +3,14 @@
 use std::{fmt, fs, path::PathBuf};
 
 use crate::{
-    codegen::{self, extract_comment_blocks_with_empty_lines, Location, Mode},
+    codegen::{self, extract_comment_blocks_with_empty_lines, Location, Mode, PREAMBLE},
     project_root, rust_files, Result,
 };
 
 pub fn generate_feature_docs(mode: Mode) -> Result<()> {
     let features = Feature::collect()?;
     let contents = features.into_iter().map(|it| it.to_string()).collect::<Vec<_>>().join("\n\n");
-    let contents = contents.trim().to_string() + "\n";
+    let contents = format!("//{}\n{}\n", PREAMBLE, contents.trim());
     let dst = project_root().join("docs/user/generated_features.adoc");
     codegen::update(&dst, &contents, mode)?;
     Ok(())
diff --git a/xtask/src/codegen/gen_syntax.rs b/xtask/src/codegen/gen_syntax.rs
index dd1f4d6a2c..df3ec22c8d 100644
--- a/xtask/src/codegen/gen_syntax.rs
+++ b/xtask/src/codegen/gen_syntax.rs
@@ -14,7 +14,7 @@ use ungrammar::{rust_grammar, Grammar, Rule};
 
 use crate::{
     ast_src::{AstEnumSrc, AstNodeSrc, AstSrc, Cardinality, Field, KindsSrc, KINDS_SRC},
-    codegen::{self, update, Mode},
+    codegen::{self, reformat, update, Mode},
     project_root, Result,
 };
 
@@ -61,7 +61,7 @@ fn generate_tokens(grammar: &AstSrc) -> Result<String> {
         }
     });
 
-    let pretty = crate::reformat(quote! {
+    let pretty = reformat(quote! {
         use crate::{SyntaxKind::{self, *}, SyntaxToken, ast::AstToken};
         #(#tokens)*
     })?
@@ -261,7 +261,7 @@ fn generate_nodes(kinds: KindsSrc<'_>, grammar: &AstSrc) -> Result<String> {
         }
     }
 
-    let pretty = crate::reformat(res)?;
+    let pretty = reformat(res)?;
     Ok(pretty)
 }
 
@@ -383,7 +383,7 @@ fn generate_syntax_kinds(grammar: KindsSrc<'_>) -> Result<String> {
         }
     };
 
-    crate::reformat(ast)
+    reformat(ast)
 }
 
 fn to_upper_snake_case(s: &str) -> String {
diff --git a/xtask/src/lib.rs b/xtask/src/lib.rs
index 807ef587ce..f3ad81ba72 100644
--- a/xtask/src/lib.rs
+++ b/xtask/src/lib.rs
@@ -62,17 +62,6 @@ pub fn run_rustfmt(mode: Mode) -> Result<()> {
     Ok(())
 }
 
-fn reformat(text: impl std::fmt::Display) -> Result<String> {
-    let _e = pushenv("RUSTUP_TOOLCHAIN", "stable");
-    ensure_rustfmt()?;
-    let stdout = run!(
-        "rustfmt --config-path {} --config fn_single_line=true", project_root().join("rustfmt.toml").display();
-        <text.to_string().as_bytes()
-    )?;
-    let preamble = "Generated file, do not edit by hand, see `xtask/src/codegen`";
-    Ok(format!("//! {}\n\n{}\n", preamble, stdout))
-}
-
 fn ensure_rustfmt() -> Result<()> {
     let out = run!("rustfmt --version")?;
     if !out.contains("stable") {