feat: custom backends through plugins

[jdx]

Add support for vfox plugins that implement backend hooks, allowing
plugins to provide custom implementations for version listing, installation,
and environment setup. This enables more flexible plugin architectures
while maintaining backward compatibility with traditional vfox plugins.

• Add BackendExecEnvContext, BackendInstallContext, and BackendListVersionsContext
• Enhance VfoxBackend to support both traditional and backend-only plugins
• Add new backend hook types in vfox crate
• Include comprehensive test coverage for vfox backend functionality
• Update plugin system to handle vfox backend plugin types

[github-actions]

Hyperfine Performance

mise x -- echo

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.7.7 x -- echo	17.8 ± 0.3	17.3	20.5	1.00
mise x -- echo	17.9 ± 0.5	17.2	22.6	1.01 ± 0.03

mise env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.7.7 env	17.3 ± 0.4	16.7	20.7	1.00
mise env	17.4 ± 0.5	16.8	23.1	1.00 ± 0.04

mise hook-env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.7.7 hook-env	16.9 ± 0.2	16.3	17.9	1.00
mise hook-env	17.2 ± 0.4	16.4	18.8	1.02 ± 0.03

mise ls

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.7.7 ls	15.2 ± 0.3	14.5	16.7	1.01 ± 0.03
mise ls	15.1 ± 0.3	14.7	16.8	1.00

xtasks/test/perf

Command	mise-2025.7.7	mise	Variance
install (uncached)	767ms	⚠️ 1003ms	-23%
install (cached)	124ms	124ms	+0%
ls (uncached)	699ms	695ms	+0%
ls (cached)	79ms	78ms	+1%
bin-paths (uncached)	703ms	⚠️ 922ms	-23%
bin-paths (cached)	64ms	64ms	+0%
task-ls (uncached)	3157ms	3498ms	-9%
task-ls (cached)	257ms	257ms	+0%

⚠️ Warning: install uncached performance variance is -23%
⚠️ Warning: bin-paths uncached performance variance is -23%

[Copilot]

Pull Request Overview

Adds support for backend-only vfox plugins by introducing dedicated backend hooks and updating core logic, CLI parsing, and documentation to handle the new plugin:tool format.

• Introduce BackendListVersionsContext, BackendInstallContext, and BackendExecEnvContext and wire up corresponding plugin hooks.
• Extend VfoxBackend and backend_type logic to detect VfoxBackend plugins and dispatch list/install/env calls to them.
• Update install state detection, CLI argument parsing, docs, e2e tests, and CI workflows to support custom backends via submodules.

Reviewed Changes

Copilot reviewed 45 out of 46 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/toolset/install_state.rs	Detect and classify backend-only plugins and switch to expect
src/plugins/mod.rs	Added VfoxBackend variant and methods in PluginType/PluginEnum
src/cli/args/backend_arg.rs	Enhanced backend argument parsing for plugin:tool format
src/backend/vfox.rs	Dispatch list/install/env calls to new backend plugin methods
src/backend/mod.rs	Update arg_to_backend to pass plugin name to VfoxBackend::from_arg
src/backend/backend_type.rs	Added VfoxBackend(String) and updated Display/guess logic
crates/vfox/src/lua_mod/hooks.rs	Registered new backend hooks (BackendListVersions, BackendInstall, BackendExecEnv)
crates/vfox/src/lua_mod/cmd.rs	Introduced cmd module for executing shell commands from plugins
crates/vfox/src/hooks/*	Added new hook modules for backend_list_versions, backend_install, backend_exec_env
crates/vfox/Cargo.toml	Bumped mlua to a beta release and updated repository URLs
.gitmodules	Added test/plugins/vfox-npm submodule
.github/workflows	Enabled submodules: true in CI workflows
e2e/backend	Added new e2e tests for vfox-npm and updated existing scripts
docs/	Added/updated docs for backend plugins, CLI reference, and architecture

Comments suppressed due to low confidence (6)

e2e/backend/test_pipx_custom_registry:39

• There's a TODO noting that this test currently only sees a warning instead of an error. We should resolve the underlying issue so the test can assert the correct failure behavior rather than leaving a placeholder.

# TODO: this is showing a warning, should be an error but I can't figure out why right now

docs/plugins.md:10

• [nitpick] The phrase "built with asdf/plugins" is ambiguous—did you mean "asdf or vfox plugins"? Consider clarifying the wording to accurately describe the legacy plugin ecosystems.

Tool plugins should be avoided for security reasons. New tools will not be accepted into mise built with asdf/plugins unless they are very popular and

xtasks/test/e2e:9

• [nitpick] You changed the flag from all to --all. If this is a breaking change, update any documentation or scripts that invoke e2e accordingly to avoid confusion.

if [[ ${1:-} == --all ]]; then

src/backend/vfox.rs:49

• New conditional logic dispatches to backend_list_versions, but there aren’t unit tests covering that code path. Add tests to ensure VfoxBackend correctly routes to plugin hooks.

    async fn _list_remote_versions(&self, config: &Arc<Config>) -> eyre::Result<Vec<String>> {

src/toolset/install_state.rs:60

• [nitpick] The has_backend_methods check only looks for backend_install.lua, so a plugin missing the other new hooks could be misclassified as a backend plugin. Consider verifying presence of all required backend hook files (backend_list_versions.lua, backend_exec_env.lua) or renaming the function to reflect the specific check.

                if has_backend_methods(&path) {

crates/vfox/Cargo.toml:25

• [nitpick] The mlua dependency is pinned to a beta release. Unless there’s a blocking issue, consider using a stable version to avoid potential instability in production.

mlua = { version = "0.11.0-beta.3", features = [

[Copilot]

[nitpick] This plugin:tool parsing block is quite large and mixes error handling for multiple plugin types. Consider refactoring into smaller helper functions or a match on plugin type to improve readability and reduce nesting.

[Copilot]

[nitpick] You removed the required flag on hook functions, so missing mandatory hooks won’t error at load time. Consider reintroducing required checks or adding explicit errors when expected hooks are absent.