feat: short circuit composition support

crates/pixi_manifest/src/task.rs

@@ -495,27 +495,28 @@ impl From<Task> for Item {
                 Item::Value(Value::InlineTable(table))
             }
             Task::Alias(alias) => {
-                let mut table = Table::new().into_inline_table();
-                table.insert(
-                    "depends-on",
-                    Value::Array(Array::from_iter(alias.depends_on.into_iter().map(|dep| {
-                        match &dep.args {
-                            Some(args) if !args.is_empty() => {
-                                let mut table = Table::new().into_inline_table();
-                                table.insert("task", dep.task_name.to_string().into());
-                                table.insert(
-                                    "args",
-                                    Value::Array(Array::from_iter(
-                                        args.iter().map(|arg| Value::from(arg.clone())),
-                                    )),
-                                );
-                                Value::InlineTable(table)
-                            }
-                            _ => Value::from(dep.task_name.to_string()),
-                        }
-                    }))),
-                );
-                Item::Value(Value::InlineTable(table))
+                let mut array = Array::new();
+                for dep in alias.depends_on.iter() {
+                    let mut table = Table::new().into_inline_table();
+
+                    table.insert("task", dep.task_name.to_string().into());
+
+                    if let Some(args) = &dep.args {
+                        table.insert(
+                            "args",
+                            Value::Array(Array::from_iter(
+                                args.iter().map(|arg| Value::from(arg.clone())),
+                            )),
+                        );
+                    }
+
+                    if let Some(env) = &dep.environment {
+                        table.insert("environment", env.to_string().into());
+                    }
+
+                    array.push(Value::InlineTable(table));
+                }
+                Item::Value(Value::Array(array))
             }
             _ => Item::None,
         }

crates/pixi_manifest/src/toml/task.rs

@@ -43,6 +43,37 @@ impl<'de> toml_span::Deserialize<'de> for TomlTask {
         let mut th = match value.take() {
             ValueInner::String(str) => return Ok(Task::Plain(str.into_owned()).into()),
             ValueInner::Table(table) => TableHelper::from((table, value.span)),
+            ValueInner::Array(array) => {
+                let mut deps = Vec::new();
+                for mut item in array {
+                    match item.take() {
+                        ValueInner::Table(table) => {
+                            let mut th = TableHelper::from((table, item.span));
+                            let name = th.required::<String>("task")?;
+                            let args = th.optional::<Vec<String>>("args");
+                            let environment = th
+                                .optional::<String>("environment")
+                                .map(|env| EnvironmentName::from_str(&env))
+                                .transpose()
+                                .map_err(|e| {
+                                    DeserError::from(expected(
+                                        "valid environment name",
+                                        ValueInner::String(e.attempted_parse.into()),
+                                        item.span,
+                                    ))
+                                })?;
+
+                            deps.push(Dependency::new(&name, args, environment));
+                        }
+                        _ => return Err(expected("table", item.take(), item.span).into()),
+                    }
+                }
+                return Ok(Task::Alias(Alias {
+                    depends_on: deps,
+                    description: None,
+                })
+                .into());
+            }
             inner => return Err(expected("string or table", inner, value.span).into()),
         };
 
@@ -58,7 +89,9 @@ impl<'de> toml_span::Deserialize<'de> for TomlTask {
                         .map(|mut item| {
                             let span = item.span;
                             match item.take() {
-                                ValueInner::String(str) => Ok(Dependency::from(str.as_ref())),
+                                ValueInner::String(str) => Ok::<Dependency, DeserError>(
+                                    Dependency::new(str.as_ref(), None, None),
+                                ),
                                 ValueInner::Table(table) => {
                                     let mut th = TableHelper::from((table, span));
                                     let name = th.required::<String>("task")?;
@@ -75,16 +108,13 @@ impl<'de> toml_span::Deserialize<'de> for TomlTask {
                                             ))
                                         })?;
 
-                                    // If the creating a new dependency fails, it means the environment name is invalid and exists hence we can safely unwrap the environment
                                     Ok(Dependency::new(&name, args, environment))
                                 }
                                 inner => Err(expected("string or table", inner, span).into()),
                             }
                         })
                         .collect::<Result<Vec<Dependency>, DeserError>>()?,
-                    ValueInner::String(str) => {
-                        vec![Dependency::from(str.as_ref())]
-                    }
+                    ValueInner::String(str) => Vec::from([Dependency::from(str.as_ref())]),
                     inner => {
                         return Err::<Vec<Dependency>, DeserError>(
                             expected("string or array", inner, value.span).into(),
@@ -129,9 +159,7 @@ impl<'de> toml_span::Deserialize<'de> for TomlTask {
                             }
                         })
                         .collect::<Result<Vec<_>, _>>()?,
-                    ValueInner::String(str) => {
-                        vec![Dependency::from(str.as_ref())]
-                    }
+                    ValueInner::String(str) => Vec::from([Dependency::from(str.as_ref())]),
                     inner => return Err(expected("string or array", inner, value.span).into()),
                 };
 

docs/source_files/pixi_tomls/pixi_task_alias.toml

@@ -0,0 +1,13 @@
+[workspace]
+channels = ["https://prefix.dev/conda-forge"]
+name = "pixi"
+platforms = ["linux-64", "win-64", "osx-64", "osx-arm64", "linux-aarch64"]
+
+# --8<-- [start:all]
+# --8<-- [start:not-all]
+[tasks]
+fmt = "ruff"
+lint = "pylint"
+# --8<-- [end:not-all]
+style = [{ task = "fmt" }, { task = "lint" }]
+# --8<-- [end:all]

docs/workspace/advanced_tasks.md

@@ -76,19 +76,28 @@ pixi task add fmt ruff
 pixi task add lint pylint
 ```
 
+```toml title="pixi.toml"
+--8<-- "docs/source_files/pixi_tomls/pixi_task_alias.toml:not-all"
+```
+
+
+### Shorthand Syntax
+
+Pixi supports a shorthand syntax for defining tasks that only depend on other tasks. Instead of using the more verbose `depends-on` field, you can define a task directly as an array of dependencies.
+
+Executing:
+
 ```
 pixi task alias style fmt lint
 ```
 
-Results in the following `pixi.toml`.
+results in the following `pixi.toml`:
 
 ```toml title="pixi.toml"
-fmt = "ruff"
-lint = "pylint"
-style = { depends-on = ["fmt", "lint"] }
+--8<-- "docs/source_files/pixi_tomls/pixi_task_alias.toml:all"
 ```
 
-Now run both tools with one command.
+Now you can run both tools with one command.
 
 ```shell
 pixi run style

schema/model.py

@@ -460,7 +460,7 @@ class Target(StrictBaseModel):
     pypi_dependencies: dict[PyPIPackageName, PyPIRequirement] | None = Field(
         None, description="The PyPI dependencies for this target"
     )
-    tasks: dict[TaskName, TaskInlineTable | NonEmptyStr] | None = Field(
+    tasks: dict[TaskName, TaskInlineTable | list[DependsOn] | NonEmptyStr] | None = Field(
         None, description="The tasks of the target"
     )
     activation: Activation | None = Field(

schema/schema.json

@@ -1556,6 +1556,12 @@
                 {
                   "$ref": "#/$defs/TaskInlineTable"
                 },
+                {
+                  "type": "array",
+                  "items": {
+                    "$ref": "#/$defs/DependsOn"
+                  }
+                },
                 {
                   "type": "string",
                   "minLength": 1

tests/integration_python/test_main_cli.py

@@ -1235,3 +1235,22 @@ def test_pixi_task_list_platforms(pixi: Path, tmp_pixi_workspace: Path) -> None:
     verify_cli_command(
         [pixi, "task", "list", "--manifest-path", manifest], stderr_contains=["foo", "bar"]
     )
+
+
+def test_pixi_add_alias(pixi: Path, tmp_pixi_workspace: Path) -> None:
+    manifest = tmp_pixi_workspace.joinpath("pixi.toml")
+    toml = """
+        [workspace]
+        name = "test"
+        channels = []
+        platforms = ["linux-64", "win-64", "osx-64"]
+        """
+    manifest.write_text(toml)
+
+    verify_cli_command([pixi, "task", "alias", "dummy-a", "dummy-b", "dummy-c", "--manifest-path", manifest])
+
+    with open(manifest, "rb") as f:
+        manifest_content = tomllib.load(f)
+
+    assert "dummy-a" in manifest_content["tasks"]
+    assert manifest_content["tasks"]["dummy-a"] == [{"task": "dummy-b"}, {"task": "dummy-c"}]

tests/integration_python/test_run_cli.py

@@ -1085,3 +1085,41 @@ def test_multiple_dependencies_with_environments(
             "0.2.0",
         ],
     )
+
+
+def test_short_circuit_composition(pixi: Path, tmp_pixi_workspace: Path) -> None:
+    """Test that short-circuiting composition works."""
+    manifest_path = tmp_pixi_workspace.joinpath("pixi.toml")
+
+    manifest_content = tomli.loads(EMPTY_BOILERPLATE_PROJECT)
+
+    manifest_content["tasks"] = {
+        "task1": "echo task1",
+        "task2": "echo task2",
+        "task3": [{"task": "task1"}],
+        "task4": [{"task": "task3"}, {"task": "task2"}],
+        "task5": {"depends-on": [{"task": "task3"}, {"task": "task2"}]},
+    }
+
+    manifest_path.write_text(tomli_w.dumps(manifest_content))
+
+    verify_cli_command(
+        [pixi, "run", "--manifest-path", manifest_path, "task4"],
+        stdout_contains=["task1", "task2"],
+    )
+
+    verify_cli_command(
+        [pixi, "run", "--manifest-path", manifest_path, "task3"],
+        stdout_contains="task1",
+    )
+
+    output1 = verify_cli_command(
+        [pixi, "run", "--manifest-path", manifest_path, "task5"],
+    )
+
+    output2 = verify_cli_command(
+        [pixi, "run", "--manifest-path", manifest_path, "task4"],
+    )
+
+    assert output1.stdout == output2.stdout
+    assert output1.stderr == output2.stderr