fix(descriptors): valid flow must have a Source and a Sink (#192)

Conceptually speaking, a data flow that has no Source will never perform any
transformation on any data as it will never receive any.

Similarly, a data flow that has no Sink will never output anything, making it a
close loop.

This commit ensures that a valid (flattened) data flow has at least one Source
and one Sink.

Signed-off-by: Julien Loudet <[email protected]>

zenoh-flow-descriptors/src/flattened/validator/mod.rs

@@ -67,6 +67,14 @@ impl<'a> Validator<'a> {
     pub(crate) fn validate(data_flow: &FlattenedDataFlowDescriptor) -> Result<()> {
         let mut this = Validator::default();
 
+        if data_flow.sources.is_empty() {
+            bail!("A data flow must specify at least ONE Source.");
+        }
+
+        if data_flow.sinks.is_empty() {
+            bail!("A data flow must specify at least ONE Sink.");
+        }
+
         for flat_source in &data_flow.sources {
             this.validate_node_id(&flat_source.id)?;
 

zenoh-flow-descriptors/src/flattened/validator/tests.rs

@@ -66,6 +66,98 @@ links:
     .is_ok());
 }
 
+#[test]
+fn test_no_source() {
+    let yaml_no_source = r#"
+name: invalid data flow no source
+
+sources:
+
+operators:
+  - id: operator
+    library: file:///home/zenoh-flow/liboperator.so
+    inputs:
+      - in-op
+    outputs:
+      - out-op
+
+sinks:
+  - id: sink
+    library: file:///home/zenoh-flow/libsink.so
+    inputs:
+      - in-si
+
+links:
+  - from:
+      node: operator
+      output: out-op
+    to:
+      node: operator
+      input: in-op
+
+  - from:
+      node: operator
+      output: out-op
+    to:
+      node: sink-1
+      input: sink-in
+"#;
+
+    let res = FlattenedDataFlowDescriptor::try_flatten(
+        serde_yaml::from_str(yaml_no_source).unwrap(),
+        Vars::default(),
+    );
+
+    assert!(res.is_err());
+    assert!(format!("{:?}", res).contains("A data flow must specify at least ONE Source."));
+}
+
+#[test]
+fn test_no_sink() {
+    let yaml_no_sink = r#"
+name: invalid data flow no sink
+
+sources:
+  - id: source
+    library: file:///home/zenoh-flow/libsource.so
+    outputs:
+      - out-so
+
+operators:
+  - id: operator
+    library: file:///home/zenoh-flow/liboperator.so
+    inputs:
+      - in-op
+    outputs:
+      - out-op
+
+sinks:
+
+links:
+  - from:
+      node: source
+      output: out-so
+    to:
+      node: operator
+      input: in-op
+
+  - from:
+      node: operator
+      output: out-op
+    to:
+      node: operator
+      input: in-op
+"#;
+
+    let res = FlattenedDataFlowDescriptor::try_flatten(
+        serde_yaml::from_str(yaml_no_sink).unwrap(),
+        Vars::default(),
+    );
+
+    assert!(res.is_err());
+    assert!(format!("{:?}", res).contains("A data flow must specify at least ONE Sink."));
+}
+
 #[test]
 fn test_duplicate_ids() {
     let yaml_duplicate_same_section = r#"