feat: add --dry-run flag to pixi lock command

crates/pixi/tests/integration_rust/common/mod.rs

@@ -718,6 +718,7 @@ impl PixiControl {
                 no_install_config: NoInstallConfig { no_install: false },
                 check: false,
                 json: false,
+                dry_run: false,
             },
         }
     }

crates/pixi_cli/src/lock.rs

@@ -29,6 +29,11 @@ pub struct Args {
     /// If yes, exit with a non-zero code.
     #[clap(long)]
     pub check: bool,
+
+    ///Compute the lock file without writing to disk.
+    /// Implies --no-install
+    #[clap(long)]
+    pub dry_run: bool,
 }
 
 pub async fn execute(args: Args) -> miette::Result<()> {
@@ -47,8 +52,12 @@ pub async fn execute(args: Args) -> miette::Result<()> {
     let original_lock_file = workspace.load_lock_file().await?.into_lock_file_or_empty();
     let (LockFileDerivedData { lock_file, .. }, lock_updated) = workspace
         .update_lock_file(UpdateLockFileOptions {
-            lock_file_usage: LockFileUsage::Update,
-            no_install: args.no_install_config.no_install,
+            lock_file_usage: if args.dry_run {
+                LockFileUsage::DryRun
+            } else {
+                LockFileUsage::Update
+            },
+            no_install: args.no_install_config.no_install || args.dry_run,
             max_concurrent_solves: workspace.config().max_concurrent_solves(),
         })
         .await?;
@@ -62,6 +71,21 @@ pub async fn execute(args: Args) -> miette::Result<()> {
         let json_diff = LockFileJsonDiff::new(Some(workspace.named_environments()), diff);
         let json = serde_json::to_string_pretty(&json_diff).expect("failed to convert to json");
         println!("{json}");
+    } else if args.dry_run {
+        if !diff.is_empty() {
+            eprintln!(
+                "{}Dry-run: lock-file would be updated (not written to disk)",
+                console::style(console::Emoji("i ", "i ")).blue()
+            );
+            diff.print()
+                .into_diagnostic()
+                .context("failed to print lock-file diff")?;
+        } else {
+            eprintln!(
+                "{}Dry-run:lock file would not change",
+                console::style(console::Emoji("i ", "i ")).blue()
+            );
+        }
     } else if lock_updated {
         eprintln!(
             "{}Updated lock-file",

crates/pixi_core/src/environment/mod.rs

@@ -461,6 +461,8 @@ pub enum LockFileUsage {
     Locked,
     /// Don't update the lock-file and don't check if it is out of date
     Frozen,
+    /// Don't update the lock-file, but don't check if it is out of date
+    DryRun,
 }
 
 impl LockFileUsage {
@@ -474,6 +476,7 @@ impl LockFileUsage {
         match self {
             LockFileUsage::Update | LockFileUsage::Locked => true,
             LockFileUsage::Frozen => false,
+            LockFileUsage::DryRun => false,
         }
     }
 }

crates/pixi_core/src/lock_file/update.rs

@@ -340,7 +340,10 @@ impl Workspace {
             .await?;
 
         // Write the lock-file to disk
-        lock_file_derived_data.write_to_disk()?;
+
+        if options.lock_file_usage != LockFileUsage::DryRun {
+            lock_file_derived_data.write_to_disk()?;
+        }
 
         Ok((lock_file_derived_data, true))
     }

docs/reference/cli/pixi/lock.md

@@ -18,6 +18,8 @@ pixi lock [OPTIONS]
 :  Output the changes in JSON format
 - <a id="arg---check" href="#arg---check">`--check`</a>
 :  Check if any changes have been made to the lock file. If yes, exit with a non-zero code
+- <a id="arg---dry-run" href="#arg---dry-run">`--dry-run`</a>
+:  Compute the lock file without writing to disk. Implies --no-install
 
 ## Update Options
 - <a id="arg---no-install" href="#arg---no-install">`--no-install`</a>