fix(swift): fall back to Ubuntu 24.04 for unsupported Ubuntu versions

[jdx]

Summary

• Swift only provides binaries for Ubuntu 20.04, 22.04, and 24.04
• On Ubuntu 26.04, the download URL 404s (ubuntu26.04 is not a valid Swift platform)
• Map unsupported Ubuntu versions to 24.04 (latest supported), matching the existing pattern for Fedora and UBI

Test plan

• Verified https://download.swift.org/.../ubuntu24.04.tar.gz returns 200
• Verified https://download.swift.org/.../ubuntu26.04.tar.gz redirects to 404

🤖 Generated with Claude Code

---

Note

Low Risk
Low risk: small, isolated change to Swift download URL/platform selection for Ubuntu; main risk is incorrect version mapping causing downloads to target the wrong Ubuntu build.

Overview
Adjusts Swift Linux platform resolution so Ubuntu uses a supported Swift binary version: introduces ubuntu_swift_version() to map unknown version_ids to 24.04.

This mapping is applied both to platform() (e.g., ubuntu24.04) and to the Ubuntu arm64 platform_directory() string (e.g., ubuntu2404-aarch64), preventing 404s when running on newer/unsupported Ubuntu releases.

^{Reviewed by Cursor Bugbot for commit ddba13f. Bugbot is set up for automated code reviews on this repo. Configure here.}

[gemini-code-assist]

Code Review

This pull request adds pkg-config to the E2E Dockerfile and introduces a mapping function for Ubuntu versions in the Swift plugin to ensure compatibility with available Swift binaries. A suggestion was made to refine the Ubuntu version mapping logic to better handle older and newer versions by setting a baseline and a cap.

[gemini-code-assist]

Instead of maintaining support for very old Ubuntu versions (like 18.04) through complex mapping, we should define a minimum supported version. This aligns with our policy of avoiding complex backward-compatibility logic for platforms older than 7 years. Consider defaulting unrecognized older versions to a baseline supported version like 20.04.

Suggested change

	fn ubuntu_swift_version(version_id: &str) -> &str {
	match version_id {
	"20.04" | "22.04" | "24.04" => version_id,
	_ => "24.04",
	}
	}
	fn ubuntu_swift_version(version_id: &str) -> &str {
	match version_id {
	"20.04" | "22.04" | "24.04" => version_id,
	v if v > "24.04" => "24.04",
	_ => "20.04",
	}
	}

References

1. When interacting with external tools, consider removing compatibility checks for very old versions (e.g., 7+ years old) if modern versions handle the functionality gracefully. Prefer documenting the minimum supported version over implementing complex backward-compatibility logic.

[greptile-apps]

Greptile Summary

This PR fixes Swift installation on Ubuntu versions not officially supported by Swift's binary distribution (e.g., Ubuntu 26.04) by adding an ubuntu_swift_version() helper that maps any unsupported version to the latest supported release (24.04), matching the existing hardcoding pattern already used for Fedora and UBI.

• Adds ubuntu_swift_version(version_id: &str) -> &str which passes through 20.04, 22.04, and 24.04 unchanged and falls back to 24.04 for everything else
• Applied consistently in both platform() (new ubuntu-specific branch) and platform_directory() (arm64 path), keeping the two in sync
• url() and verify_gpg() both derive from these functions, so the corrected version propagates to the tarball URL and the GPG signature URL alike
• No unit tests were added for the new helper, despite the file already containing a mod tests block with tests for other pure functions

Confidence Score: 5/5

Safe to merge; the fix is minimal, correct, and non-breaking for all currently supported Ubuntu versions

Single-file change with a simple pure mapping function. Supported Ubuntu versions (20.04/22.04/24.04) pass through unchanged, so no regression for existing users. Unsupported versions now resolve to a valid Swift binary URL instead of 404ing. Logic is consistent between platform() and platform_directory(). Matches the established pattern used for Fedora and UBI hardcoding.

No files require special attention

Important Files Changed

Filename	Overview
src/plugins/core/swift.rs	Adds ubuntu_swift_version() helper to map unsupported Ubuntu versions to 24.04; correctly applied in both platform() and platform_directory(), no regressions for currently-supported versions

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Install Swift on Linux] --> B{os_release.id?}
    B -->|ubuntu| C[ubuntu_swift_version\nversion_id]
    B -->|amzn| D[amazonlinuxVER]
    B -->|ubi| E[ubi9 hardcoded]
    B -->|fedora| F[fedora39 hardcoded]
    B -->|other| G[id + version_id]
    C --> H{version_id\nin 20.04 / 22.04 / 24.04?}
    H -->|yes| I[use version_id as-is]
    H -->|no e.g. 26.04| J[fallback → 24.04]
    I --> K[Build tarball + sig URL]
    J --> K
    D --> K
    E --> K
    F --> K
    G --> K

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_{Reviews (1): Last reviewed commit: "fix(swift): fall back to Ubuntu 24.04 fo..." | Re-trigger Greptile}

[greptile-apps]

Consider adding unit tests for ubuntu_swift_version

The file already has a mod tests block (used for resolve_pkgutil_path). ubuntu_swift_version is a pure function — boundary cases like "20.04", "22.04", "24.04", and "26.04" are trivial to assert and would guard against accidental future edits (e.g., adding "18.04" support or changing the fallback version).

Suggested change

	fn ubuntu_swift_version(version_id: &str) -> &str {
	match version_id {
	"20.04" | "22.04" | "24.04" => version_id,
	_ => "24.04",
	}
	}
	/// Swift only provides Ubuntu binaries for specific versions.
	/// Map unsupported Ubuntu versions to the latest supported one.
	fn ubuntu_swift_version(version_id: &str) -> &str {
	match version_id {
	"20.04" | "22.04" | "24.04" => version_id,
	_ => "24.04",
	}
	}
	#[cfg(test)]
	mod ubuntu_version_tests {
	use super::ubuntu_swift_version;
	#[test]
	fn supported_versions_pass_through() {
	assert_eq!(ubuntu_swift_version("20.04"), "20.04");
	assert_eq!(ubuntu_swift_version("22.04"), "22.04");
	assert_eq!(ubuntu_swift_version("24.04"), "24.04");
	}
	#[test]
	fn unsupported_version_falls_back_to_24_04() {
	assert_eq!(ubuntu_swift_version("26.04"), "24.04");
	assert_eq!(ubuntu_swift_version("18.04"), "24.04");
	assert_eq!(ubuntu_swift_version("99.99"), "24.04");
	}
	}

_{Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!}

[gemini-code-assist]

Code Review

This pull request adds pkg-config to the E2E Dockerfile and updates the Swift plugin to correctly handle Ubuntu version mapping for binary downloads. It introduces a helper function to map unsupported Ubuntu versions to the nearest supported release, defaulting to 24.04. I have no feedback to provide as there were no review comments.

[github-actions]

Hyperfine Performance

mise x -- echo

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2026.4.3 x -- echo	21.4 ± 0.3	21.0	24.5	1.00
mise x -- echo	21.9 ± 0.4	21.3	24.8	1.02 ± 0.02

mise env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2026.4.3 env	21.0 ± 0.4	20.4	25.5	1.00
mise env	21.3 ± 0.2	20.7	22.8	1.01 ± 0.02

mise hook-env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2026.4.3 hook-env	21.6 ± 0.2	21.1	24.5	1.00
mise hook-env	22.0 ± 0.3	21.5	25.2	1.02 ± 0.02

mise ls

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2026.4.3 ls	19.0 ± 0.4	18.5	24.3	1.00
mise ls	19.4 ± 0.2	19.0	22.8	1.02 ± 0.02

xtasks/test/perf

Command	mise-2026.4.3	mise	Variance
install (cached)	145ms	146ms	+0%
ls (cached)	76ms	76ms	+0%
bin-paths (cached)	80ms	80ms	+0%
task-ls (cached)	823ms	790ms	+4%