feat(cli): add --staged flag

CHANGELOG.md

@@ -167,6 +167,12 @@ our [guidelines for writing a good changelog entry](https://github.com/biomejs/b
   ```
   </details>
 
+- Added new `--staged` flag to the `check`, `format` and `lint` subcommands.
+
+  This new option allows users to apply the command _only_ to the files that are staged (the
+  ones that will be committed), which can be very useful to simplify writing git hook scripts
+  such as `pre-commit`. Contributed by @castarco
+
 #### Enhancements
 
 - Improve support of `.prettierignore` when migrating from Prettier

crates/biome_cli/src/changed.rs

@@ -27,3 +27,13 @@ pub(crate) fn get_changed_files(
 
     Ok(filtered_changed_files)
 }
+
+pub(crate) fn get_staged_files(
+    fs: &DynRef<'_, dyn FileSystem>,
+) -> Result<Vec<OsString>, CliDiagnostic> {
+    let staged_files = fs.get_staged_files()?;
+
+    let filtered_staged_files = staged_files.iter().map(OsString::from).collect::<Vec<_>>();
+
+    Ok(filtered_staged_files)
+}

crates/biome_cli/src/commands/check.rs

@@ -1,6 +1,7 @@
-use crate::changed::get_changed_files;
 use crate::cli_options::CliOptions;
-use crate::commands::{get_stdin, resolve_manifest, validate_configuration_diagnostics};
+use crate::commands::{
+    get_files_to_process, get_stdin, resolve_manifest, validate_configuration_diagnostics,
+};
 use crate::{
     execute_mode, setup_cli_subscriber, CliDiagnostic, CliSession, Execution, TraversalMode,
 };
@@ -26,6 +27,7 @@ pub(crate) struct CheckCommandPayload {
     pub(crate) formatter_enabled: Option<bool>,
     pub(crate) linter_enabled: Option<bool>,
     pub(crate) organize_imports_enabled: Option<bool>,
+    pub(crate) staged: bool,
     pub(crate) changed: bool,
     pub(crate) since: Option<String>,
 }
@@ -46,6 +48,7 @@ pub(crate) fn check(
         organize_imports_enabled,
         formatter_enabled,
         since,
+        staged,
         changed,
     } = payload;
     setup_cli_subscriber(cli_options.log_level, cli_options.log_kind);
@@ -120,13 +123,12 @@ pub(crate) fn check(
 
     let stdin = get_stdin(stdin_file_path, &mut *session.app.console, "check")?;
 
-    if since.is_some() && !changed {
-        return Err(CliDiagnostic::incompatible_arguments("since", "changed"));
+    if let Some(_paths) =
+        get_files_to_process(since, changed, staged, &session.app.fs, &fs_configuration)?
+    {
+        paths = _paths;
     }
 
-    if changed {
-        paths = get_changed_files(&session.app.fs, &fs_configuration, since)?;
-    }
     session
         .app
         .workspace

crates/biome_cli/src/commands/format.rs

@@ -1,6 +1,7 @@
-use crate::changed::get_changed_files;
 use crate::cli_options::CliOptions;
-use crate::commands::{get_stdin, resolve_manifest, validate_configuration_diagnostics};
+use crate::commands::{
+    get_files_to_process, get_stdin, resolve_manifest, validate_configuration_diagnostics,
+};
 use crate::diagnostics::DeprecatedArgument;
 use crate::{
     execute_mode, setup_cli_subscriber, CliDiagnostic, CliSession, Execution, TraversalMode,
@@ -30,6 +31,7 @@ pub(crate) struct FormatCommandPayload {
     pub(crate) write: bool,
     pub(crate) cli_options: CliOptions,
     pub(crate) paths: Vec<OsString>,
+    pub(crate) staged: bool,
     pub(crate) changed: bool,
     pub(crate) since: Option<String>,
 }
@@ -51,6 +53,7 @@ pub(crate) fn format(
         mut json_formatter,
         mut css_formatter,
         since,
+        staged,
         changed,
     } = payload;
     setup_cli_subscriber(cli_options.log_level, cli_options.log_kind);
@@ -156,12 +159,10 @@ pub(crate) fn format(
     let (vcs_base_path, gitignore_matches) =
         configuration.retrieve_gitignore_matches(&session.app.fs, vcs_base_path.as_deref())?;
 
-    if since.is_some() && !changed {
-        return Err(CliDiagnostic::incompatible_arguments("since", "changed"));
-    }
-
-    if changed {
-        paths = get_changed_files(&session.app.fs, &configuration, since)?;
+    if let Some(_paths) =
+        get_files_to_process(since, changed, staged, &session.app.fs, &configuration)?
+    {
+        paths = _paths;
     }
 
     session

crates/biome_cli/src/commands/lint.rs

@@ -1,6 +1,7 @@
-use crate::changed::get_changed_files;
 use crate::cli_options::CliOptions;
-use crate::commands::{get_stdin, resolve_manifest, validate_configuration_diagnostics};
+use crate::commands::{
+    get_files_to_process, get_stdin, resolve_manifest, validate_configuration_diagnostics,
+};
 use crate::{
     execute_mode, setup_cli_subscriber, CliDiagnostic, CliSession, Execution, TraversalMode,
 };
@@ -24,6 +25,7 @@ pub(crate) struct LintCommandPayload {
     pub(crate) files_configuration: Option<PartialFilesConfiguration>,
     pub(crate) paths: Vec<OsString>,
     pub(crate) stdin_file_path: Option<String>,
+    pub(crate) staged: bool,
     pub(crate) changed: bool,
     pub(crate) since: Option<String>,
 }
@@ -39,6 +41,7 @@ pub(crate) fn lint(session: CliSession, payload: LintCommandPayload) -> Result<(
         stdin_file_path,
         vcs_configuration,
         files_configuration,
+        staged,
         changed,
         since,
     } = payload;
@@ -95,12 +98,10 @@ pub(crate) fn lint(session: CliSession, payload: LintCommandPayload) -> Result<(
     let (vcs_base_path, gitignore_matches) =
         fs_configuration.retrieve_gitignore_matches(&session.app.fs, vcs_base_path.as_deref())?;
 
-    if since.is_some() && !changed {
-        return Err(CliDiagnostic::incompatible_arguments("since", "changed"));
-    }
-
-    if changed {
-        paths = get_changed_files(&session.app.fs, &fs_configuration, since)?;
+    if let Some(_paths) =
+        get_files_to_process(since, changed, staged, &session.app.fs, &fs_configuration)?
+    {
+        paths = _paths;
     }
 
     let stdin = get_stdin(stdin_file_path, &mut *session.app.console, "lint")?;

crates/biome_cli/src/commands/mod.rs

@@ -1,3 +1,4 @@
+use crate::changed::{get_changed_files, get_staged_files};
 use crate::cli_options::{cli_options, CliOptions, ColorsArg};
 use crate::diagnostics::DeprecatedConfigurationFile;
 use crate::execute::Stdin;
@@ -14,11 +15,11 @@ use biome_configuration::{
 use biome_configuration::{ConfigurationDiagnostic, PartialConfiguration};
 use biome_console::{markup, Console, ConsoleExt};
 use biome_diagnostics::{Diagnostic, PrintDiagnostic};
-use biome_fs::BiomePath;
+use biome_fs::{BiomePath, FileSystem};
 use biome_service::configuration::LoadedConfiguration;
 use biome_service::documentation::Doc;
 use biome_service::workspace::{OpenProjectParams, UpdateProjectParams};
-use biome_service::WorkspaceError;
+use biome_service::{DynRef, WorkspaceError};
 use bpaf::Bpaf;
 use std::ffi::OsString;
 use std::path::PathBuf;
@@ -109,6 +110,11 @@ pub enum BiomeCommand {
         #[bpaf(long("stdin-file-path"), argument("PATH"), hide_usage)]
         stdin_file_path: Option<String>,
 
+        /// When set to true, only the files that have been staged (the ones prepared to be committed)
+        /// will be linted.
+        #[bpaf(long("staged"), switch)]
+        staged: bool,
+
         /// When set to true, only the files that have been changed compared to your `defaultBranch`
         /// configuration will be linted.
         #[bpaf(long("changed"), switch)]
@@ -150,6 +156,10 @@ pub enum BiomeCommand {
         /// Example: `echo 'let a;' | biome lint --stdin-file-path=file.js`
         #[bpaf(long("stdin-file-path"), argument("PATH"), hide_usage)]
         stdin_file_path: Option<String>,
+        /// When set to true, only the files that have been staged (the ones prepared to be committed)
+        /// will be linted.
+        #[bpaf(long("staged"), switch)]
+        staged: bool,
         /// When set to true, only the files that have been changed compared to your `defaultBranch`
         /// configuration will be linted.
         #[bpaf(long("changed"), switch)]
@@ -197,6 +207,11 @@ pub enum BiomeCommand {
         #[bpaf(switch)]
         write: bool,
 
+        /// When set to true, only the files that have been staged (the ones prepared to be committed)
+        /// will be linted.
+        #[bpaf(long("staged"), switch)]
+        staged: bool,
+
         /// When set to true, only the files that have been changed compared to your `defaultBranch`
         /// configuration will be linted.
         #[bpaf(long("changed"), switch)]
@@ -510,6 +525,34 @@ pub(crate) fn get_stdin(
     Ok(stdin)
 }
 
+fn get_files_to_process(
+    since: Option<String>,
+    changed: bool,
+    staged: bool,
+    fs: &DynRef<'_, dyn FileSystem>,
+    configuration: &PartialConfiguration,
+) -> Result<Option<Vec<OsString>>, CliDiagnostic> {
+    if since.is_some() {
+        if !changed {
+            return Err(CliDiagnostic::incompatible_arguments("since", "changed"));
+        }
+        if staged {
+            return Err(CliDiagnostic::incompatible_arguments("since", "staged"));
+        }
+    }
+
+    if changed {
+        if staged {
+            return Err(CliDiagnostic::incompatible_arguments("changed", "staged"));
+        }
+        Ok(Some(get_changed_files(fs, configuration, since)?))
+    } else if staged {
+        Ok(Some(get_staged_files(fs)?))
+    } else {
+        Ok(None)
+    }
+}
+
 /// Tests that all CLI options adhere to the invariants expected by `bpaf`.
 #[test]
 fn check_options() {

crates/biome_cli/src/lib.rs

@@ -88,6 +88,7 @@ impl<'app> CliSession<'app> {
                 linter_enabled,
                 organize_imports_enabled,
                 formatter_enabled,
+                staged,
                 changed,
                 since,
             } => commands::check::check(
@@ -102,6 +103,7 @@ impl<'app> CliSession<'app> {
                     linter_enabled,
                     organize_imports_enabled,
                     formatter_enabled,
+                    staged,
                     changed,
                     since,
                 },
@@ -115,6 +117,7 @@ impl<'app> CliSession<'app> {
                 stdin_file_path,
                 vcs_configuration,
                 files_configuration,
+                staged,
                 changed,
                 since,
             } => commands::lint::lint(
@@ -128,6 +131,7 @@ impl<'app> CliSession<'app> {
                     stdin_file_path,
                     vcs_configuration,
                     files_configuration,
+                    staged,
                     changed,
                     since,
                 },
@@ -165,6 +169,7 @@ impl<'app> CliSession<'app> {
                 files_configuration,
                 json_formatter,
                 css_formatter,
+                staged,
                 changed,
                 since,
             } => commands::format::format(
@@ -180,6 +185,7 @@ impl<'app> CliSession<'app> {
                     files_configuration,
                     json_formatter,
                     css_formatter,
+                    staged,
                     changed,
                     since,
                 },