Add manifest_version validation to fastly.toml parsing.

CHANGELOG.md

@@ -12,6 +12,7 @@
 - Update to Rust 2024 Edition. ([#588](https://github.com/fastly/Viceroy/pull/588))
 - Add stub implementations for bot detection hostcalls. ([#592](https://github.com/fastly/Viceroy/pull/592))
 - Add no-op implementations for stale-if-error hostcalls ([#591](https://github.com/fastly/Viceroy/pull/591))
+- Add `manifest_version` validation to fastly.toml parsing. ([#590](https://github.com/fastly/Viceroy/pull/590))
 
 ## 0.16.4 (2026-01-26)
 

Cargo.toml

@@ -46,7 +46,6 @@ regex = "^1.3.9"
 rustls = "^0.21.1"
 rustls-native-certs = "^0.6.3"
 rustls-pemfile = "^1.0.3"
-semver = "^0.10.0"
 serde = "^1.0.145"
 serde_derive = "^1.0.114"
 serde_json = { workspace = true }

src/config.rs

@@ -163,6 +163,7 @@ impl FromStr for FastlyConfig {
 /// [fromt-str]: https://docs.rs/toml/latest/toml/de/fn.from_str.html
 #[derive(Deserialize)]
 struct TomlFastlyConfig {
+    manifest_version: Option<u32>,
     local_server: Option<RawLocalServerConfig>,
     // AJT 2020.03.10: the following fields are marked as optional because, for the time being,
     // we are not expecting to actually use the fastly.toml manifest, but instead use a separate
@@ -175,16 +176,30 @@ struct TomlFastlyConfig {
     language: Option<String>,
 }
 
+/// Manifest versions greater than this are not yet supported.
+const MAX_MANIFEST_VERSION: u32 = 3;
+
 impl TryInto<FastlyConfig> for TomlFastlyConfig {
     type Error = FastlyConfigError;
     fn try_into(self) -> Result<FastlyConfig, Self::Error> {
         let Self {
+            manifest_version,
             name,
             description,
             authors,
             language,
             local_server,
         } = self;
+
+        if let Some(manifest_version) = manifest_version {
+            if manifest_version > MAX_MANIFEST_VERSION {
+                return Err(FastlyConfigError::UnsupportedManifestVersion(
+                    manifest_version,
+                    MAX_MANIFEST_VERSION,
+                ));
+            }
+        }
+
         let local_server = local_server
             .map(TryInto::try_into)
             .transpose()?

src/config/unit_tests.rs

@@ -57,7 +57,7 @@ fn fastly_toml_files_can_be_read() {
 fn fastly_toml_files_with_simple_backend_configurations_can_be_read() {
     let config = FastlyConfig::from_str(
         r#"
-            manifest_version = "1.2.3"
+            manifest_version = 3
             name = "backend-config-example"
             description = "a toml example with backend configuration"
             authors = [
@@ -111,7 +111,7 @@ fn fastly_toml_files_with_simple_dictionary_configurations_can_be_read() {
     writeln!(file, "{{}}").unwrap();
     let config = FastlyConfig::from_str(format!(
         r#"
-            manifest_version = "1.2.3"
+            manifest_version = 3
             name = "dictionary-config-example"
             description = "a toml example with dictionary configuration"
             authors = [
@@ -150,7 +150,7 @@ fn fastly_toml_files_with_simple_config_store_configurations_can_be_read() {
     writeln!(file, "{{}}").unwrap();
     let config = FastlyConfig::from_str(format!(
         r#"
-            manifest_version = "1.2.3"
+            manifest_version = 3
             name = "dictionary-config-example"
             description = "a toml example with config store configuration"
             authors = [
@@ -1216,3 +1216,20 @@ Qq7tJAMLnPnAdAUousI0RDcLpB8adGkhZH66lL4oV9U+aQ0dA0oiqSKZtMoHeWbr
         assert_eq!(3, shark_backend.ca_certs.len());
     }
 }
+
+#[test]
+fn fastly_toml_files_with_unsupported_manifest_version() {
+    let err = FastlyConfig::from_str(
+        r#"
+            manifest_version = 4
+            name = "backend-config-example"
+            language = "rust"
+    "#,
+    )
+    .expect_err("an unsupported manifest_version should have evoked an error");
+
+    assert!(matches!(
+        err,
+        FastlyConfigError::UnsupportedManifestVersion(4, 3)
+    ));
+}

src/error.rs

@@ -429,14 +429,10 @@ pub enum FastlyConfigError {
     #[error("error parsing `fastly.toml`: {0}")]
     InvalidFastlyToml(#[from] toml::de::Error),
 
-    /// An error caused by an invalid manifest version.
-    ///
-    /// This means that the provided version is not compliant with the semver spec. See the
-    /// documentation of [`semver::Version::parse`][parse-errors] for more information.
-    ///
-    /// [parse-errors]: https://docs.rs/semver/latest/semver/struct.Version.html#errors
-    #[error("invalid manifest version: {0}")]
-    InvalidManifestVersion(#[from] semver::SemVerError),
+    /// The `manifest_version` field contained a value greater than is
+    /// currently supported.
+    #[error("unsupported manifest version {0}; max supported version is {1}")]
+    UnsupportedManifestVersion(u32, u32),
 }
 
 /// Errors that may occur while validating acl configurations.