feat: Add env to the tasks to specify tasks specific environment variables

docs/features/advanced_tasks.md

@@ -167,6 +167,34 @@ Note: if you want to debug the globs you can use the `--verbose` flag to see whi
 pixi run -v start
 ```
 
+## Environment variables
+You can set environment variables for a task.
+These are seen as "default" values for the variables as you can overwrite them from the shell.
+
+```toml title="pixi.toml"
+[tasks]
+echo = { cmd = "echo $ARGUMENT", env = { ARGUMENT = "hello" } }
+```
+If you run `pixi run echo` it will output `hello`.
+When you set the environment variable `ARGUMENT` before running the task, it will use that value instead.
+
+```shell
+ARGUMENT=world pixi run echo
+✨ Pixi task (echo in default): echo $ARGUMENT
+world
+```
+
+These variables are not shared over tasks, so you need to define these for every task you want to use them in.
+
+!!! note "Extend instead of overwrite"
+    If you use the same environment variable in the value as in the key of the map you will also overwrite the variable.
+    For example overwriting a `PATH`
+    ```toml title="pixi.toml"
+    [tasks]
+    echo = { cmd = "echo $PATH", env = { PATH = "/tmp/path:$PATH" } }
+    ```
+    This will output `/tmp/path:/usr/bin:/bin` instead of the original `/usr/bin:/bin`.
+
 ## Our task runner: deno_task_shell
 
 To support the different OS's (Windows, OSX and Linux), pixi integrates a shell that can run on all of them.

docs/reference/configuration.md

@@ -173,6 +173,9 @@ simple = "echo This is a simple task"
 cmd = { cmd="echo Same as a simple task but now more verbose"}
 depending = { cmd="echo run after simple", depends_on="simple"}
 alias = { depends_on=["depending"]}
+download = { cmd="curl -o file.txt https://example.com/file.txt" , outputs=["file.txt"]}
+build = { cmd="npm build", cwd="frontend", inputs=["frontend/package.json", "frontend/*.js"]}
+run = { cmd="python run.py $ARGUMENT", env={ ARGUMENT="value" }}
 ```
 
 You can modify this table using [`pixi task`](cli.md#task).

examples/ros2-nav2/pixi.toml

@@ -6,8 +6,9 @@ authors = ["Ruben Arts <ruben@prefix.dev>"]
 channels = ["conda-forge", "robostack-staging"]
 platforms = ["linux-64", "osx-arm64", "osx-64"]
 
-[tasks]
-start = {cmd="export GAZEBO_MODEL_PATH=$GAZEBO_MODEL_PATH:$PIXI_PROJECT_ROOT/.pixi/env/share/turtlebot3_gazebo/models && export TURTLEBOT3_MODEL=waffle && ros2 launch nav2_bringup tb3_simulation_launch.py headless:=False"}
+[tasks.start]
+env = { GAZEBO_MODEL_PATH = "$GAZEBO_MODEL_PATH:$PIXI_PROJECT_ROOT/.pixi/env/share/turtlebot3_gazebo/models", TURTLEBOT3_MODEL = "waffle" }
+cmd="ros2 launch nav2_bringup tb3_simulation_launch.py headless:=False"
 
 [dependencies]
 ros-humble-desktop = "*"

schema/examples/valid/full.toml

@@ -47,6 +47,7 @@ test3 = { cmd = "pytest", depends_on = ["test2"] }
 test4 = { cmd = "pytest", cwd = "tests", depends_on = ["test2"] }
 test5 = { cmd = "pytest" }
 test6 = { depends_on = ["test5"] }
+test7 = { cmd = "pytest", cwd = "tests", depends_on = ["test5"], env = {PYTHONPATH = "bla", "WEIRD_STRING" = "blu"}}
 
 [system-requirements]
 linux = "5.10"

schema/model.py

@@ -213,6 +213,9 @@ class TaskInlineTable(StrictBaseModel):
     outputs: list[Glob] | None = Field(
         None, description="A list of glob patterns that are generated by this command"
     )
+    env: dict[NonEmptyStr, NonEmptyStr] | None = Field(
+        None, description="A map of environment variables to values, used in the task, these will be overwritten by the shell." , examples = [{"key": "value"}, {"ARGUMENT": "value"}]
+    )
 
 
 #######################

schema/schema.json

@@ -1285,6 +1285,31 @@
           "default": null,
           "description": "A list of glob patterns that are generated by this command",
           "title": "Outputs"
+        },
+        "env": {
+          "anyOf": [
+            {
+              "additionalProperties": {
+                "minLength": 1,
+                "type": "string"
+              },
+              "type": "object"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "default": null,
+          "description": "A map of environment variables to values, used in the task, these will be overwritten by the shell.",
+          "examples": [
+            {
+              "key": "value"
+            },
+            {
+              "ARGUMENT": "value"
+            }
+          ],
+          "title": "Env"
         }
       },
       "title": "TaskInlineTable",

src/cli/task.rs

@@ -125,6 +125,7 @@ impl From<AddArgs> for Task {
                 inputs: None,
                 outputs: None,
                 cwd: value.cwd,
+                env: Default::default(),
             })
         }
     }

src/task/executable_task.rs

@@ -122,9 +122,23 @@ impl<'p> ExecutableTask<'p> {
             return Ok(None);
         };
 
+        // Append the environment variables if they don't exist
+        let mut export = String::new();
+        if let Some(env) = self.task.env() {
+            for (key, value) in env {
+                if value.contains(format!("${}", key).as_str())
+                    || std::env::var(key.as_str()).is_err()
+                {
+                    tracing::info!("Setting environment variable: {}={}", key, value);
+                    export.push_str(&format!("export {}={};\n", key, value));
+                }
+                tracing::info!("Environment variable {} already set", key);
+            }
+        }
+
         // Append the command line arguments
         let cli_args = quote_arguments(self.additional_args.iter().map(|arg| arg.as_str()));
-        let full_script = format!("{task} {cli_args}");
+        let full_script = format!("{export}\n{task} {cli_args}");
 
         // Parse the shell command
         deno_task_shell::parser::parse(full_script.trim())

src/task/mod.rs

@@ -2,6 +2,7 @@ use itertools::Itertools;
 use serde::{Deserialize, Serialize};
 use serde_with::{formats::PreferMany, serde_as, OneOrMany};
 use std::borrow::Cow;
+use std::collections::HashMap;
 use std::fmt::{Display, Formatter};
 use std::path::{Path, PathBuf};
 
@@ -129,6 +130,16 @@ impl Task {
         }
     }
 
+    /// Returns the environment variables for the task to run in.
+    pub fn env(&self) -> Option<&HashMap<String, String>> {
+        match self {
+            Task::Plain(_) => None,
+            Task::Custom(_) => None,
+            Task::Execute(exe) => exe.env.as_ref(),
+            Task::Alias(_) => None,
+        }
+    }
+
     /// Returns the working directory for the task to run in.
     pub fn working_directory(&self) -> Option<&Path> {
         match self {
@@ -167,6 +178,9 @@ pub struct Execute {
 
     /// The working directory for the command relative to the root of the project.
     pub cwd: Option<PathBuf>,
+
+    /// A list of environment variables to set before running the command
+    pub env: Option<HashMap<String, String>>,
 }
 
 impl From<Execute> for Task {