fix(backend): change dependency checks to warnings instead of errors

[jdx]

Summary

This PR fixes Windows CI failures where dependency checks were failing due to platform-specific command resolution issues (e.g., npm.cmd vs npm).

Problem

The backends were preemptively checking for dependencies using which, which on Windows was failing to find commands that have platform-specific extensions (like npm.cmd). This was causing mise i to fail on Windows CI even when the dependencies were actually available.

Solution

Instead of preemptively failing when dependencies are not found, the backends now show warning messages but continue execution. This allows:

• The actual commands to fail with their native error messages if dependencies are truly missing
• Avoids false positives from path resolution issues on Windows
• Better user experience with warnings instead of hard failures

Changes

• Renamed ensure_dependency to warn_if_dependency_missing in Backend trait
• Updated all backends (npm, cargo, go, gem, pipx, spm, dotnet) to use warnings instead of errors for missing deps
• Updated e2e test to expect warnings instead of errors

Fixes

CI failure on Windows: https://github.com/jdx/mise/actions/runs/17896504421

🤖 Generated with Claude Code

[Copilot]

Pull Request Overview

This PR fixes Windows CI failures by changing dependency checks from errors to warnings across all package manager backends. The issue was that Windows was failing to find commands with platform-specific extensions (like npm.cmd) using which, causing false positive failures.

Key changes:

• Renamed ensure_dependency to warn_if_dependency_missing across all backends
• Changed return type from Result<()> to unit type, removing error propagation
• Updated error messages to use warnings instead of hard failures

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/backend/mod.rs	Updated trait method from error-returning to warning-only
src/backend/npm.rs	Changed npm dependency checks to warnings
src/backend/cargo.rs	Changed cargo dependency checks to warnings
src/backend/go.rs	Changed go dependency checks to warnings
src/backend/gem.rs	Changed gem dependency checks to warnings
src/backend/pipx.rs	Changed pipx dependency checks to warnings
src/backend/spm.rs	Changed swift dependency checks to warnings
src/backend/dotnet.rs	Changed dotnet dependency checks to warnings
e2e/backend/test_backend_missing_deps	Updated test to expect warnings instead of errors

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[github-actions]

Hyperfine Performance

mise x -- echo

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.9.14 x -- echo	20.2 ± 0.4	19.4	23.1	1.00
mise x -- echo	20.6 ± 0.4	19.5	22.7	1.02 ± 0.03

mise env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.9.14 env	20.0 ± 0.6	19.1	25.0	1.00
mise env	20.2 ± 0.4	19.0	22.1	1.01 ± 0.04

mise hook-env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.9.14 hook-env	19.6 ± 0.3	18.7	21.3	1.00
mise hook-env	19.7 ± 1.0	18.3	35.3	1.00 ± 0.05

mise ls

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.9.14 ls	17.7 ± 0.9	16.9	33.2	1.00
mise ls	18.2 ± 0.6	16.8	21.0	1.03 ± 0.06

xtasks/test/perf

Command	mise-2025.9.14	mise	Variance
install (cached)	175ms	✅ 106ms	+65%
ls (cached)	65ms	64ms	+1%
bin-paths (cached)	71ms	71ms	+0%
task-ls (cached)	485ms	478ms	+1%

✅ Performance improvement: install cached is 65%