Fix runtime_manifest field not working with Scarb <0.5.0 (#686)

scarb-metadata/src/lib.rs

@@ -137,6 +137,13 @@ pub struct Metadata {
     pub target_dir: Option<Utf8PathBuf>,
 
     /// Path to the manifest of package or workspace that Scarb has been run from.
+    ///
+    /// ## Compatibility
+    ///
+    /// With very old Scarb versions (`<0.5.0`), this field may end up being empty path upon
+    /// deserializing from `scarb metadata` call.
+    /// In this case, fall back to [`WorkspaceMetadata.manifest`][WorkspaceMetadata] field value.
+    #[serde(default)]
     pub runtime_manifest: Utf8PathBuf,
 
     /// Current workspace metadata.

utils/scarb-ui/src/args/packages_filter.rs

@@ -226,6 +226,11 @@ impl PackagesSource for Metadata {
     }
 
     fn runtime_manifest(&self) -> Utf8PathBuf {
-        self.runtime_manifest.clone()
+        let path = self.runtime_manifest.clone();
+        if !path.as_str().is_empty() {
+            path
+        } else {
+            self.workspace.manifest_path.clone()
+        }
     }
 }