engineering: Improve COSI Metadata Parsing #394

frhuelsz · 2025-12-11T01:23:43Z

🔍 Description

Remove deny_unknown_fields for forwards compatibility
Introduce an enum of known cosi versions to ensure we keep track of what is expected of each
Parse spec enums as rust enums.

Copilot

Pull request overview

This PR improves COSI metadata parsing by enhancing type safety and forward compatibility. The changes introduce strongly-typed enums for bootloader types and versions, replace string comparisons with enum matching, and remove deny_unknown_fields to allow graceful handling of future metadata fields.

Key changes:

Introduced KnownMetadataVersion enum to track supported COSI specification versions
Replaced string-based bootloader type checks with BootloaderType and SystemdBootLoaderType enums
Removed deny_unknown_fields from all structs for forward compatibility

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crates/trident/src/osimage/cosi/metadata.rs

ndubchak · 2025-12-11T22:20:47Z

crates/trident/src/osimage/cosi/metadata.rs

                }
+
+                // Valid combination
+                _ => {}


What is this for?

this is the wildcard for all non-error conditions, this whole statement is only trying to match on error conditions

fintelia · 2025-12-11T18:23:26Z

crates/trident/src/osimage/cosi/metadata.rs

+
+                // Unknown bootloader type is invalid
+                (BootloaderType::Unknown(bootloader_type), _) => {
+                    bail!("Unsupported bootloader type: {}", bootloader_type);


This should only bail if the version is equal to 1.1. Otherwise we can't add new bootloader types.

This is more about this version of trident not recognizing this bootloader type. If we see something we don't recognize then we have no idea what to do with it?

I'd feel better about running this once we know the specific operation we're doing with the COSI. Perhaps directly in the validate() method of the subsystem that is using the bootloader field?

For something like trident stream-image it might not matter and would present a forward compatibility concern

Fair. This is the existing logic that was implemented before, but happy to revise for forward compat.

I did some extra future proofing, basically we will always validate the metadata as long as it's technically valid, regardless of the support offered by the version of Trident.

Copilot

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

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crates/trident/src/osimage/cosi/metadata.rs

Copilot · 2025-12-11T22:48:52Z

crates/trident/src/osimage/cosi/metadata.rs

+    #[serde(untagged)]
+    Unknown(String),
+}
+


The BootloaderType enum should derive Display like SystemdBootloaderType does (line 367) for consistency and to enable more ergonomic error messages. Currently, line 148 uses the inner String value from the Unknown variant, but with Display, the enum could be used directly in format strings for all variants.

Suggested change

use std::fmt;

impl fmt::Display for BootloaderType {

fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

match self {

BootloaderType::SystemdBoot => write!(f, "systemd-boot"),

BootloaderType::Grub => write!(f, "grub"),

BootloaderType::Unknown(s) => write!(f, "{s}"),

}

}

}

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 5 comments.

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Copilot · 2025-12-12T01:18:30Z

crates/trident/src/osimage/cosi/metadata.rs

+                    match systemd_boot.entries.as_slice() {
+                        // No entries is invalid
+                        [] => bail!("Bootloader type 'systemd-boot' must not be empty"),
+


There's trailing whitespace on line 129 after the pattern match. Consider removing it for code cleanliness.

Suggested change

Copilot · 2025-12-12T01:18:30Z

crates/trident/src/osimage/cosi/metadata.rs

+impl PartialOrd for MetadataVersion {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for MetadataVersion {
+    fn cmp(&self, other: &Self) -> Ordering {
+        match self.major.cmp(&other.major) {
+            Ordering::Equal => self.minor.cmp(&other.minor),
+            ord => ord,
+        }
+    }
+}


The new Ord and PartialOrd implementations for MetadataVersion lack test coverage. Consider adding tests to verify the comparison behavior works correctly, especially for edge cases like comparing different major versions and different minor versions.

Copilot · 2025-12-12T01:18:31Z

crates/trident/src/osimage/cosi/metadata.rs

+pub(crate) enum BootloaderType {
+    #[serde(rename = "systemd-boot")]
+    SystemdBoot,
+
+    #[serde(rename = "grub")]
+    Grub,
+
+    #[serde(untagged)]
+    Unknown(String),
+}


The new BootloaderType enum and its deserialization behavior (especially the Unknown variant) lacks test coverage. Consider adding tests to verify that known bootloader types deserialize correctly and unknown types are properly captured in the Unknown variant.

Copilot · 2025-12-12T01:18:31Z

crates/trident/src/osimage/cosi/metadata.rs

+pub(crate) enum SystemdBootloaderType {
+    #[serde(rename = "uki-standalone")]
+    #[strum(to_string = "uki-standalone")]
+    UkiStandalone,
+
+    #[serde(rename = "uki-config")]
+    #[strum(to_string = "uki-config")]
+    UkiConfig,
+
+    #[serde(rename = "config")]
+    #[strum(to_string = "config")]
+    Config,
+
+    #[serde(untagged)]
+    #[strum(to_string = "{0}")]
+    Unknown(String),
+}


The new SystemdBootloaderType enum and its deserialization behavior (especially the Unknown variant and the Display trait) lacks test coverage. Consider adding tests to verify that known boot types deserialize correctly, unknown types are captured properly, and the Display trait produces the expected string representations.

Copilot · 2025-12-12T01:18:31Z

crates/trident/src/osimage/cosi/metadata.rs

+        // Validate bootloader on COSI version >= 1.1
+        if self.version >= KnownMetadataVersion::V1_1.as_version() {
+            let Some(bootloader) = self.bootloader.as_ref() else {
+                bail!("Bootloader metadata is required for COSI version >= 1.1, but not provided");
+            };
+
+            match (&bootloader.bootloader_type, &bootloader.systemd_boot) {
+                // Grub with systemd-boot entries is invalid
+                (BootloaderType::Grub, Some(_)) => {
+                    bail!("Bootloader type 'grub' cannot have systemd-boot entries");
+                }
+
+                // Systemd-boot without entries is invalid
+                (BootloaderType::SystemdBoot, None) => {
+                    bail!("Bootloader type 'systemd-boot' requires systemd-boot entries");
+                }
+
+                // Systemd-boot with not exactly 1 UKI entry is invalid for this version of Trident
+                (BootloaderType::SystemdBoot, Some(systemd_boot)) => {
+                    match systemd_boot.entries.as_slice() {
+                        // No entries is invalid
+                        [] => bail!("Bootloader type 'systemd-boot' must not be empty"),
+
+                        // More than one entry, is not allowed in this version of Trident.
+                        [_, _, ..] => {
+                            bail!("Multiple bootloader entries are not supported for bootloader type 'systemd-boot' in this version of Trident");
                        }
+
+                        // One entry of type other than uki-standalone is invalid
+                        [entry] if !entry.boot_type.eq(&SystemdBootloaderType::UkiStandalone) => bail!(
+                            "Bootloader type 'systemd-boot' only supports 'uki-standalone' entry type, found: {}",
+                            entry.boot_type
+                        ),
+
+                        // Exactly one uki-standalone entry is valid
+                        [ _ ] => {}
                    }
-                    _ => bail!("Unsupported bootloader type: {}", bootloader_type),
                }
-            }
-            None => {
-                if self.version.major > 1 || (self.version.major == 1 && self.version.minor > 0) {
-                    bail!("Bootloader is required for COSI version >= 1.1, but not provided");
+
+                // Unknown bootloader type is invalid
+                (BootloaderType::Unknown(bootloader_type), _) => {
+                    bail!("Unsupported bootloader type: {}", bootloader_type);
                }
+
+                // Valid combination
+                _ => {}
            }
        }


The refactored bootloader validation logic lacks test coverage for the various edge cases, including: validation with COSI version >= 1.1, Grub with systemd-boot entries, systemd-boot without entries, systemd-boot with empty entries, systemd-boot with multiple entries, systemd-boot with non-UKI entry types, and unknown bootloader types. Consider adding comprehensive tests for these validation scenarios.

frhuelsz added 2 commits December 10, 2025 17:19

improve metadata parsing

9c5ba4b

remove deny unknown fields

7964d99

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improvements

31e3d84

fintelia mentioned this pull request Dec 11, 2025

Create COSI 1.2 with fields needed for 'baremetal images' #393

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ndubchak reviewed Dec 11, 2025

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Merge similar match arms

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Update crates/trident/src/osimage/cosi/metadata.rs

d0292d1

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot AI review requested due to automatic review settings December 12, 2025 01:15

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Future proofing

5225f15

+use std::fmt;
+impl fmt::Display for BootloaderType {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            BootloaderType::SystemdBoot => write!(f, "systemd-boot"),
+            BootloaderType::Grub => write!(f, "grub"),
+            BootloaderType::Unknown(s) => write!(f, "{s}"),
+        }
+    }
+}

engineering: Improve COSI Metadata Parsing #394

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frhuelsz commented Dec 11, 2025

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