Deny unknown fields (#272) (#349)

Author: BrianBorge

Diff for: buildpacks/ruby/src/layers/shared.rs

@@ -207,6 +207,7 @@ mod tests {
 
     /// Struct for asserting the behavior of `cached_layer_write_metadata`
     #[derive(Debug, serde::Serialize, serde::Deserialize, Clone)]
+    #[serde(deny_unknown_fields)]
     struct TestMetadata {
         value: String,
     }

Diff for: buildpacks/ruby/src/main.rs

@@ -285,6 +285,7 @@ impl From<RubyBuildpackError> for libcnb::Error<RubyBuildpackError> {
 buildpack_main!(RubyBuildpack);
 
 #[derive(serde::Deserialize, serde::Serialize, Debug, Clone, PartialEq, Eq)]
+#[serde(deny_unknown_fields)]
 struct BundleWithout(String);
 
 impl BundleWithout {

Diff for: commons/src/gemfile_lock.rs

@@ -81,6 +81,7 @@ impl GemfileLock {
 }
 
 #[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
+#[serde(deny_unknown_fields)]
 pub struct ResolvedRubyVersion(pub String);
 
 impl Display for ResolvedRubyVersion {
@@ -90,6 +91,7 @@ impl Display for ResolvedRubyVersion {
 }
 
 #[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
+#[serde(deny_unknown_fields)]
 pub struct ResolvedBundlerVersion(pub String);
 
 impl Display for ResolvedBundlerVersion {

Diff for: commons/src/metadata_digest.rs

@@ -148,6 +148,7 @@ const PLATFORM_ENV_VAR: &str = "user configured environment variables";
 /// add logic to your buildpack to re-run that command similar to the "escape valve" discussed
 /// above, but triggered by buildpack author instead of the end user.
 #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq, Default)]
+#[serde(deny_unknown_fields)]
 pub struct MetadataDigest {
     platform_env: Option<PlatformEnvDigest>,
     files: Option<PathsDigest>, // Must be last for serde to be happy https://github.com/toml-rs/toml-rs/issues/142
@@ -235,9 +236,11 @@ impl MetadataDigest {
 }
 
 #[derive(Serialize, Deserialize, Clone, Debug, Hash, PartialEq, Eq)]
+#[serde(deny_unknown_fields)]
 struct ShaString(String);
 
 #[derive(Serialize, Deserialize, Clone, Debug, Hash, PartialEq, Eq)]
+#[serde(deny_unknown_fields)]
 struct PlatformEnvDigest(ShaString);
 impl PlatformEnvDigest {
     fn new(platform: &impl Platform) -> Self {
@@ -248,6 +251,7 @@ impl PlatformEnvDigest {
 }
 
 #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq, Default)]
+#[serde(deny_unknown_fields)]
 struct PathsDigest(HashMap<PathBuf, ShaString>);
 
 /// Main struct for detecting changes between two iterations