feat(rust/signed-doc): ChainRule mutual exclusive with the CollaboratorsRule (#649)

* ChainRule mutual exclusive with the CollaboratorsRule

* Move the check to the constructor

* Fix formatting

Author: stanislav-tkach

rust/signed_doc/src/validator/rules/chain/mod.rs

@@ -1,6 +1,10 @@
 //! `chain` rule type impl.
 
-use catalyst_signed_doc_spec::{is_required::IsRequired, metadata::chain::Chain};
+use anyhow::ensure;
+use catalyst_signed_doc_spec::{
+    is_required::IsRequired,
+    metadata::{chain::Chain, collaborators::Collaborators},
+};
 
 use crate::{CatalystSignedDocument, providers::CatalystSignedDocumentProvider};
 
@@ -21,16 +25,24 @@ pub(crate) enum ChainRule {
 
 impl ChainRule {
     /// Generating `ChainRule` from specs
-    pub(crate) fn new(spec: &Chain) -> Self {
+    pub(crate) fn new(
+        spec: &Chain,
+        collaborators_spec: &Collaborators,
+    ) -> anyhow::Result<Self> {
         let optional = match spec.required {
             IsRequired::Yes => false,
             IsRequired::Optional => true,
             IsRequired::Excluded => {
-                return Self::NotSpecified;
+                return Ok(Self::NotSpecified);
             },
         };
 
-        Self::Specified { optional }
+        ensure!(
+            matches!(collaborators_spec.required, IsRequired::Excluded),
+            "Chained Documents do not support collaborators"
+        );
+
+        Ok(Self::Specified { optional })
     }
 
     /// Field validation rule

rust/signed_doc/src/validator/rules/chain/tests.rs

@@ -1,3 +1,4 @@
+use catalyst_signed_doc_spec::{is_required::IsRequired, metadata::chain::Chain as ChainSpec};
 use catalyst_types::uuid::{UuidV4, UuidV7};
 use test_case::test_case;
 
@@ -48,6 +49,17 @@ async fn test_without_chaining_documents() {
     assert!(!rule.check(&doc, &provider).await.unwrap());
 }
 
+#[tokio::test]
+async fn chain_rule_collaborators_rule_conflict() {
+    let chain = ChainSpec {
+        required: IsRequired::Optional,
+    };
+    let collaborators = Collaborators {
+        required: IsRequired::Optional,
+    };
+    ChainRule::new(&chain, &collaborators).unwrap_err();
+}
+
 #[test_case(
     {
         let doc_type = UuidV4::new();

rust/signed_doc/src/validator/rules/mod.rs

@@ -129,7 +129,7 @@ impl Rules {
             content_encoding: ContentEncodingRule::new(&doc_spec.headers.content_encoding)?,
             template: TemplateRule::new(all_docs_specs, &doc_spec.metadata.template)?,
             parameters: ParametersRule::new(all_docs_specs, &doc_spec.metadata.parameters)?,
-            chain: ChainRule::new(&doc_spec.metadata.chain),
+            chain: ChainRule::new(&doc_spec.metadata.chain, &doc_spec.metadata.collaborators)?,
             doc_ref: RefRule::new(all_docs_specs, &doc_spec.metadata.doc_ref)?,
             reply: ReplyRule::new(all_docs_specs, &doc_spec.metadata.reply)?,
             section: SectionRule::NotSpecified,