feat: implement --force flag for lock

crates/uv-cli/src/lib.rs

@@ -3728,6 +3728,10 @@ pub struct LockArgs {
     #[arg(long, conflicts_with = "check_exists", conflicts_with = "check")]
     pub dry_run: bool,
 
+    /// Force rewrite
+    #[arg(long, conflicts_with = "dry_run")]
+    pub force: bool,
+
     /// Lock the specified Python script, rather than the current project.
     ///
     /// If provided, uv will lock the script (based on its inline metadata table, in adherence with

crates/uv/src/commands/project/add.rs

@@ -980,7 +980,7 @@ async fn lock_and_sync(
         if locked {
             LockMode::Locked(target.interpreter())
         } else {
-            LockMode::Write(target.interpreter())
+            LockMode::Write(target.interpreter(), false)
         },
         &settings.resolver,
         client_builder,
@@ -1102,7 +1102,7 @@ async fn lock_and_sync(
                 if locked {
                     LockMode::Locked(target.interpreter())
                 } else {
-                    LockMode::Write(target.interpreter())
+                    LockMode::Write(target.interpreter(), false)
                 },
                 &settings.resolver,
                 client_builder,

crates/uv/src/commands/project/export.rs

@@ -180,7 +180,7 @@ pub(crate) async fn export(
         // If we're locking a script, avoid creating a lockfile if it doesn't already exist.
         LockMode::DryRun(interpreter.as_ref().unwrap())
     } else {
-        LockMode::Write(interpreter.as_ref().unwrap())
+        LockMode::Write(interpreter.as_ref().unwrap(), false)
     };
 
     // Initialize any shared state.

crates/uv/src/commands/project/lock.rs

@@ -85,6 +85,7 @@ pub(crate) async fn lock(
     frozen: bool,
     dry_run: DryRun,
     refresh: Refresh,
+    force: bool,
     python: Option<String>,
     install_mirrors: PythonInstallMirrors,
     settings: ResolverSettings,
@@ -182,7 +183,7 @@ pub(crate) async fn lock(
         } else if dry_run.enabled() {
             LockMode::DryRun(&interpreter)
         } else {
-            LockMode::Write(&interpreter)
+            LockMode::Write(&interpreter, force)
         }
     };
 
@@ -253,7 +254,7 @@ pub(crate) async fn lock(
 #[derive(Debug, Clone, Copy)]
 pub(super) enum LockMode<'env> {
     /// Write the lockfile to disk.
-    Write(&'env Interpreter),
+    Write(&'env Interpreter, bool),
     /// Perform a resolution, but don't write the lockfile to disk.
     DryRun(&'env Interpreter),
     /// Error if the lockfile is not up-to-date with the project requirements.
@@ -359,6 +360,7 @@ impl<'env> LockOperation<'env> {
                     self.workspace_cache,
                     self.printer,
                     self.preview,
+                    false,
                 )
                 .await?;
 
@@ -372,7 +374,7 @@ impl<'env> LockOperation<'env> {
 
                 Ok(result)
             }
-            LockMode::Write(interpreter) | LockMode::DryRun(interpreter) => {
+            LockMode::Write(interpreter, force) => {
                 // Read the existing lockfile.
                 let existing = match target.read().await {
                     Ok(Some(existing)) => Some(existing),
@@ -402,16 +404,50 @@ impl<'env> LockOperation<'env> {
                     self.workspace_cache,
                     self.printer,
                     self.preview,
+                    force,
                 )
                 .await?;
 
-                // If the lockfile changed, write it to disk.
-                if !matches!(self.mode, LockMode::DryRun(_)) {
-                    if let LockResult::Changed(_, lock) = &result {
-                        target.commit(lock).await?;
-                    }
+                if let LockResult::Changed(_, lock) = &result {
+                    target.commit(lock).await?;
                 }
 
+                Ok(result)
+            }
+            LockMode::DryRun(interpreter) => {
+                // Read the existing lockfile.
+                let existing = match target.read().await {
+                    Ok(Some(existing)) => Some(existing),
+                    Ok(None) => None,
+                    Err(ProjectError::Lock(err)) => {
+                        warn_user!(
+                            "Failed to read existing lockfile; ignoring locked requirements: {err}"
+                        );
+                        None
+                    }
+                    Err(err) => return Err(err),
+                };
+
+                // Perform the lock operation, but don't write the lockfile to disk.
+                let result = do_lock(
+                    target,
+                    interpreter,
+                    existing,
+                    self.constraints,
+                    self.refresh,
+                    self.settings,
+                    self.client_builder,
+                    self.state,
+                    self.logger,
+                    self.concurrency,
+                    self.cache,
+                    self.workspace_cache,
+                    self.printer,
+                    self.preview,
+                    false,
+                )
+                .await?;
+
                 Ok(result)
             }
         }
@@ -434,6 +470,7 @@ async fn do_lock(
     workspace_cache: &WorkspaceCache,
     printer: Printer,
     preview: Preview,
+    force: bool,
 ) -> Result<LockResult, ProjectError> {
     let start = std::time::Instant::now();
 
@@ -767,6 +804,7 @@ async fn do_lock(
             state.index(),
             &database,
             printer,
+            force,
         )
         .await
         {
@@ -986,11 +1024,16 @@ impl ValidatedLock {
         index: &InMemoryIndex,
         database: &DistributionDatabase<'_, Context>,
         printer: Printer,
+        force: bool,
     ) -> Result<Self, ProjectError> {
         // Perform checks in a deliberate order, such that the most extreme conditions are tested
         // first (i.e., every check that returns `Self::Unusable`, followed by every check that
         // returns `Self::Versions`, followed by every check that returns `Self::Preferable`, and
         // finally `Self::Satisfies`).
+        if force {
+            return Ok(Self::Preferable(lock));
+        }
+        // Start with the most severe condition: a fundamental option changed between resolutions.
         if lock.resolution_mode() != options.resolution_mode {
             let _ = writeln!(
                 printer.stderr(),

crates/uv/src/commands/project/remove.rs

@@ -294,7 +294,7 @@ pub(crate) async fn remove(
     let mode = if locked {
         LockMode::Locked(target.interpreter())
     } else {
-        LockMode::Write(target.interpreter())
+        LockMode::Write(target.interpreter(), false)
     };
 
     // Initialize any shared state.

crates/uv/src/commands/project/run.rs

@@ -266,7 +266,7 @@ hint: If you are running a script with `{}` in the shebang, you may need to incl
             } else if locked {
                 LockMode::Locked(environment.interpreter())
             } else {
-                LockMode::Write(environment.interpreter())
+                LockMode::Write(environment.interpreter(), false)
             };
 
             // Generate a lockfile.
@@ -744,7 +744,7 @@ hint: If you are running a script with `{}` in the shebang, you may need to incl
                 } else if isolated {
                     LockMode::DryRun(venv.interpreter())
                 } else {
-                    LockMode::Write(venv.interpreter())
+                    LockMode::Write(venv.interpreter(), false)
                 };
 
                 let result = match project::lock::LockOperation::new(

crates/uv/src/commands/project/sync.rs

@@ -309,7 +309,7 @@ pub(crate) async fn sync(
     } else if dry_run.enabled() {
         LockMode::DryRun(environment.interpreter())
     } else {
-        LockMode::Write(environment.interpreter())
+        LockMode::Write(environment.interpreter(), false)
     };
 
     let lock_target = match &target {
@@ -1272,7 +1272,7 @@ impl From<(&LockTarget<'_>, &LockMode<'_>, &Outcome)> for LockReport {
                         LockResult::Unchanged(..) => match mode {
                             // When `--frozen` is used, we don't check the lockfile
                             LockMode::Frozen => LockAction::Use,
-                            LockMode::DryRun(_) | LockMode::Locked(_) | LockMode::Write(_) => {
+                            LockMode::DryRun(_) | LockMode::Locked(_) | LockMode::Write(..) => {
                                 LockAction::Check
                             }
                         },

crates/uv/src/commands/project/tree.rs

@@ -131,7 +131,7 @@ pub(crate) async fn tree(
         // If we're locking a script, avoid creating a lockfile if it doesn't already exist.
         LockMode::DryRun(interpreter.as_ref().unwrap())
     } else {
-        LockMode::Write(interpreter.as_ref().unwrap())
+        LockMode::Write(interpreter.as_ref().unwrap(), false)
     };
 
     // Initialize any shared state.

crates/uv/src/commands/project/version.rs

@@ -582,7 +582,7 @@ async fn lock_and_sync(
     let mode = if locked {
         LockMode::Locked(target.interpreter())
     } else {
-        LockMode::Write(target.interpreter())
+        LockMode::Write(target.interpreter(), false)
     };
 
     // Initialize any shared state.

crates/uv/src/lib.rs

@@ -1934,6 +1934,7 @@ async fn run_project(
                 args.frozen,
                 args.dry_run,
                 args.refresh,
+                args.force,
                 args.python,
                 args.install_mirrors,
                 args.settings,

crates/uv/src/settings.rs

@@ -1381,6 +1381,7 @@ pub(crate) struct LockSettings {
     pub(crate) locked: bool,
     pub(crate) frozen: bool,
     pub(crate) dry_run: DryRun,
+    pub(crate) force: bool,
     pub(crate) script: Option<PathBuf>,
     pub(crate) python: Option<String>,
     pub(crate) install_mirrors: PythonInstallMirrors,
@@ -1400,6 +1401,7 @@ impl LockSettings {
             check,
             check_exists,
             dry_run,
+            force,
             script,
             resolver,
             build,
@@ -1416,6 +1418,7 @@ impl LockSettings {
             locked: check,
             frozen: check_exists,
             dry_run: DryRun::from_args(dry_run),
+            force,
             script,
             python: python.and_then(Maybe::into_option),
             refresh: Refresh::from(refresh),

crates/uv/tests/it/show_settings.rs

@@ -9501,6 +9501,7 @@ fn upgrade_project_cli_config_interaction() -> anyhow::Result<()> {
         locked: false,
         frozen: false,
         dry_run: Disabled,
+        force: false,
         script: None,
         python: None,
         install_mirrors: PythonInstallMirrors {
@@ -9618,6 +9619,7 @@ fn upgrade_project_cli_config_interaction() -> anyhow::Result<()> {
         locked: false,
         frozen: false,
         dry_run: Disabled,
+        force: false,
         script: None,
         python: None,
         install_mirrors: PythonInstallMirrors {
@@ -9758,6 +9760,7 @@ fn upgrade_project_cli_config_interaction() -> anyhow::Result<()> {
         locked: false,
         frozen: false,
         dry_run: Disabled,
+        force: false,
         script: None,
         python: None,
         install_mirrors: PythonInstallMirrors {
@@ -9873,6 +9876,7 @@ fn upgrade_project_cli_config_interaction() -> anyhow::Result<()> {
         locked: false,
         frozen: false,
         dry_run: Disabled,
+        force: false,
         script: None,
         python: None,
         install_mirrors: PythonInstallMirrors {
@@ -9978,6 +9982,7 @@ fn upgrade_project_cli_config_interaction() -> anyhow::Result<()> {
         locked: false,
         frozen: false,
         dry_run: Disabled,
+        force: false,
         script: None,
         python: None,
         install_mirrors: PythonInstallMirrors {
@@ -10084,6 +10089,7 @@ fn upgrade_project_cli_config_interaction() -> anyhow::Result<()> {
         locked: false,
         frozen: false,
         dry_run: Disabled,
+        force: false,
         script: None,
         python: None,
         install_mirrors: PythonInstallMirrors {

docs/reference/cli.md

@@ -1669,7 +1669,8 @@ uv lock [OPTIONS]
 <p>May also be set with the <code>UV_EXTRA_INDEX_URL</code> environment variable.</p></dd><dt id="uv-lock--find-links"><a href="#uv-lock--find-links"><code>--find-links</code></a>, <code>-f</code> <i>find-links</i></dt><dd><p>Locations to search for candidate distributions, in addition to those found in the registry indexes.</p>
 <p>If a path, the target must be a directory that contains packages as wheel files (<code>.whl</code>) or source distributions (e.g., <code>.tar.gz</code> or <code>.zip</code>) at the top level.</p>
 <p>If a URL, the page must contain a flat list of links to package files adhering to the formats described above.</p>
-<p>May also be set with the <code>UV_FIND_LINKS</code> environment variable.</p></dd><dt id="uv-lock--fork-strategy"><a href="#uv-lock--fork-strategy"><code>--fork-strategy</code></a> <i>fork-strategy</i></dt><dd><p>The strategy to use when selecting multiple versions of a given package across Python versions and platforms.</p>
+<p>May also be set with the <code>UV_FIND_LINKS</code> environment variable.</p></dd><dt id="uv-lock--force"><a href="#uv-lock--force"><code>--force</code></a></dt><dd><p>Force rewrite</p>
+</dd><dt id="uv-lock--fork-strategy"><a href="#uv-lock--fork-strategy"><code>--fork-strategy</code></a> <i>fork-strategy</i></dt><dd><p>The strategy to use when selecting multiple versions of a given package across Python versions and platforms.</p>
 <p>By default, uv will optimize for selecting the latest version of each package for each supported Python version (<code>requires-python</code>), while minimizing the number of selected versions across platforms.</p>
 <p>Under <code>fewest</code>, uv will minimize the number of selected versions for each package, preferring older versions that are compatible with a wider range of supported Python versions or platforms.</p>
 <p>May also be set with the <code>UV_FORK_STRATEGY</code> environment variable.</p><p>Possible values:</p>