twoliter: improve callsite clarity of ImageResolver

Switches to a builder-style mechanism for disabling metadata fetching.
Since Rust doesn't have named args, it can be hard to know what boolean
function flags do at a callsite without going to the function signature.

twoliter/src/lock/image.rs

@@ -204,6 +204,7 @@ impl ImageResolverImpl for OverriddenImage {
 #[derive(Debug)]
 pub struct ImageResolver {
     image_resolver_impl: Box<dyn ImageResolverImpl>,
+    skip_metadata_retrieval: bool,
 }
 
 impl ImageResolver {
@@ -244,6 +245,7 @@ impl ImageResolver {
                     },
                 })
             },
+            skip_metadata_retrieval: false,
         })
     }
 
@@ -289,9 +291,18 @@ impl ImageResolver {
                     },
                 })
             },
+            skip_metadata_retrieval: false,
         })
     }
 
+    /// Skip metadata retrieval when resolving images.
+    ///
+    /// This is useful for SDKs, which don't store image metadata (no deps.)
+    pub(crate) fn skip_metadata_retrieval(mut self) -> Self {
+        self.skip_metadata_retrieval = true;
+        self
+    }
+
     /// Calculate the digest of the locked image
     async fn calculate_digest(&self, image_tool: &ImageTool) -> Result<String> {
         let image_uri = self.image_resolver_impl.uri();
@@ -317,7 +328,6 @@ impl ImageResolver {
     pub(crate) async fn resolve(
         &self,
         image_tool: &ImageTool,
-        skip_metadata: bool,
     ) -> Result<(LockedImage, Option<ImageMetadata>)> {
         // First get the manifest list
         let uri = self.image_resolver_impl.uri();
@@ -336,7 +346,7 @@ impl ImageResolver {
             digest: self.calculate_digest(image_tool).await?,
         };
 
-        if skip_metadata {
+        if self.skip_metadata_retrieval {
             return Ok((locked_image, None));
         }
 

twoliter/src/lock/mod.rs

@@ -100,7 +100,8 @@ impl LockedSDK {
         debug!(?sdk, "Resolving workspace SDK");
         let image_tool = ImageTool::from_environment()?;
         ImageResolver::from_image(&sdk, project)?
-            .resolve(&image_tool, true)
+            .skip_metadata_retrieval() // SDKs don't have metadata
+            .resolve(&image_tool)
             .await
             .map(|(sdk, _)| Some(Self(sdk)))
     }
@@ -284,7 +285,7 @@ impl Lock {
                     image.version.clone(),
                 );
                 let image_resolver = ImageResolver::from_image(image, project)?;
-                let (locked_image, metadata) = image_resolver.resolve(&image_tool, false).await?;
+                let (locked_image, metadata) = image_resolver.resolve(&image_tool).await?;
                 let metadata = metadata.context(format!(
                     "failed to validate kit image with name {} from vendor {}",
                     locked_image.name, locked_image.vendor
@@ -313,7 +314,8 @@ impl Lock {
 
         debug!(?sdk, "Resolving workspace SDK");
         let (sdk, _metadata) = ImageResolver::from_image(sdk, project)?
-            .resolve(&image_tool, true)
+            .skip_metadata_retrieval() // SDKs don't have metadata
+            .resolve(&image_tool)
             .await?;
 
         Ok(Self {