Add output_path field to Task::Options struct

This commit adds `output_path` field to `Task::Options` struct. This
is needed to partially address request golemfactory/g-flite#28. The
field is made optional, and serialized only if is not `None`.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "gwasm-api"
-version = "0.1.1"
+version = "0.1.2"
 authors = ["Golem RnD Team <[email protected]>"]
 edition = "2018"
 license = "GPL-3.0"

src/task.rs

@@ -55,6 +55,7 @@ pub struct TaskBuilder<'a> {
     subtask_timeout: Option<Timeout>,
     input_dir_path: PathBuf,
     output_dir_path: PathBuf,
+    output_path: Option<PathBuf>,
     subtask_data: Vec<Vec<u8>>,
 }
 
@@ -69,6 +70,7 @@ impl<'a> TaskBuilder<'a> {
             subtask_timeout: None,
             input_dir_path: workspace.as_ref().join("in"),
             output_dir_path: workspace.as_ref().join("out"),
+            output_path: None,
             subtask_data: Vec::new(),
         }
     }
@@ -97,6 +99,13 @@ impl<'a> TaskBuilder<'a> {
         self
     }
 
+    /// Sets task's expected output path, i.e., where the final result of
+    /// the task is meant to land
+    pub fn output_path<P: AsRef<Path>>(mut self, output_path: P) -> Self {
+        self.output_path = Some(output_path.as_ref().into());
+        self
+    }
+
     /// Pushes subtask data into the buffer
     ///
     /// Note that each pushed chunk of `data` is equivalent to one
@@ -132,6 +141,7 @@ impl<'a> TaskBuilder<'a> {
             wasm_name,
             self.input_dir_path.clone(),
             self.output_dir_path.clone(),
+            self.output_path.clone(),
         );
 
         // create input dir
@@ -274,6 +284,8 @@ pub struct Options {
     input_dir_path: PathBuf,
     #[serde(rename = "output_dir")]
     output_dir_path: PathBuf,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    output_path: Option<PathBuf>,
     subtasks: BTreeMap<String, Subtask>,
 }
 
@@ -284,12 +296,14 @@ impl Options {
         wasm_name: S,
         input_dir_path: P,
         output_dir_path: P,
+        output_path: Option<P>,
     ) -> Self {
         Self {
             js_name: js_name.into(),
             wasm_name: wasm_name.into(),
             input_dir_path: input_dir_path.into(),
             output_dir_path: output_dir_path.into(),
+            output_path: output_path.map(Into::into),
             subtasks: BTreeMap::new(),
         }
     }
@@ -314,6 +328,12 @@ impl Options {
         &self.output_dir_path
     }
 
+    /// Path to the dir where the final output of the task
+    /// is expected
+    pub fn output_path(&self) -> Option<&Path> {
+        self.output_path.as_ref().map(AsRef::as_ref)
+    }
+
     /// Returns an [`Iterator`] over created [`Subtask`]'s
     ///
     /// [`Subtask`]: ../task/struct.Subtask.html