From 041eb6d2aab5a612c0191f750e9402fd846e3997 Mon Sep 17 00:00:00 2001
From: Noam Gottlieb <noamgo@mobileye.com>
Date: Tue, 11 Feb 2025 01:09:48 +0200
Subject: [PATCH] feat: Added dry-run flag to pixi run + docs + test

---
 docs/reference/cli.md                    |  3 +++
 src/cli/run.rs                           | 22 ++++++++++++++++++++++
 tests/integration_python/test_run_cli.py | 20 ++++++++++++++++++++
 3 files changed, 45 insertions(+)

diff --git a/docs/reference/cli.md b/docs/reference/cli.md
index 89df0b07d..3f0434ac3 100644
--- a/docs/reference/cli.md
+++ b/docs/reference/cli.md
@@ -297,6 +297,7 @@ You cannot run `pixi run source setup.bash` as `source` is not available in the
 - `--concurrent-downloads`: The number of concurrent downloads to use when installing packages. Defaults to 50.
 - `--concurrent-solves`: The number of concurrent solves to use when installing packages. Defaults to the number of cpu threads.
 - `--skip-deps`: Skip the dependencies of the task, which where defined in the `depends-on` field of the task.
+- `--dry-run (-n)`: Run the task in dry-run mode (only print the command that would run)
 
 ```shell
 pixi run python
@@ -310,6 +311,8 @@ pixi run build
 pixi run task argument1 argument2
 # Skip dependencies of the task
 pixi run --skip-deps task
+# Run in dry-run mode to see the commands that would be run
+pixi run --dry-run task
 
 # If you have multiple environments you can select the right one with the --environment flag.
 pixi run --environment cuda python
diff --git a/src/cli/run.rs b/src/cli/run.rs
index 4f9604900..bf0928e28 100644
--- a/src/cli/run.rs
+++ b/src/cli/run.rs
@@ -66,6 +66,10 @@ pub struct Args {
     #[arg(long)]
     pub skip_deps: bool,
 
+    /// Run the task in dry-run mode (only print the command that would run)
+    #[clap(short = 'n', long)]
+    pub dry_run: bool,
+
     #[clap(long, action = clap::ArgAction::HelpLong)]
     pub help: Option<bool>,
 
@@ -151,6 +155,18 @@ pub async fn execute(args: Args) -> miette::Result<()> {
 
     tracing::info!("Task graph: {}", task_graph);
 
+    // Print dry-run message if dry-run mode is enabled
+    if args.dry_run {
+        eprintln!(
+            "{}{}",
+            console::Emoji("🌵 ", ""),
+            console::style("Dry-run mode enabled - no tasks will be executed.")
+                .yellow()
+                .bold(),
+        );
+        eprintln!();
+    }
+
     // Traverse the task graph in topological order and execute each individual
     // task.
     let mut task_idx = 0;
@@ -196,6 +212,12 @@ pub async fn execute(args: Args) -> miette::Result<()> {
             );
         }
 
+        // on dry-run mode, we just print the command and skip the execution
+        if args.dry_run {
+            task_idx += 1;
+            continue;
+        }
+
         // check task cache
         let task_cache = match executable_task
             .can_skip(&lock_file.lock_file)
diff --git a/tests/integration_python/test_run_cli.py b/tests/integration_python/test_run_cli.py
index b0ff26452..2cea6d777 100644
--- a/tests/integration_python/test_run_cli.py
+++ b/tests/integration_python/test_run_cli.py
@@ -352,3 +352,23 @@ def test_run_help(pixi: Path, tmp_pixi_workspace: Path) -> None:
         [pixi, "run", "python", "--help"],
         stdout_contains="python",
     )
+
+
+def test_run_dry_run(pixi: Path, tmp_pixi_workspace: Path) -> None:
+    manifest = tmp_pixi_workspace.joinpath("pixi.toml")
+    toml = f"""
+    {EMPTY_BOILERPLATE_PROJECT}
+    [activation.env]
+    DRY_RUN_TEST_VAR = "WET"
+    [tasks]
+    dry-run-task = "echo $DRY_RUN_TEST_VAR"
+    """
+    manifest.write_text(toml)
+
+    # Run the task with --dry-run flag
+    verify_cli_command(
+        [pixi, "run", "--manifest-path", manifest, "--dry-run", "dry-run-task"],
+        stderr_contains="$DRY_RUN_TEST_VAR",
+        stdout_excludes="WET",
+        stderr_excludes="WET",
+    )