feat(binary): onPost hook — runs after install/update by fentas · Pull Request #153 · fentas/b

fentas · 2026-05-07T20:58:09Z

Summary

Per-binary post-install/update hook. A shell command that runs after a successful download, with context about what happened.

Usage

CLI:

b install --add github.com/arg-sh/argsh --on-post 'argsh builtin ${B_EVENT}'

b.yaml:

binaries:
  github.com/arg-sh/argsh:
    onPost: argsh builtin ${B_EVENT}

Environment variables

The hook receives:

Variable	Description	Example
`B_EVENT`	`install` or `update`	`install`
`B_NAME`	Binary name	`argsh`
`B_VERSION`	Version being installed	`v0.6.6`
`B_FILE`	Absolute path to the binary	`/project/.bin/argsh`

Behaviour

Runs in the project root directory
Only after successful download (not on skip, not on failure)
Non-zero exit → warning on stderr, not a fatal error
Skipped on `--dry-run`
`--on-post` flag persists to b.yaml when used with `--add`

Use cases

Shell completion generation: `kubectl completion bash > .completions/kubectl.bash`
Plugin/builtin updates: `argsh builtin update`
Post-install validation: `helm version --client`
Config scaffolding: `tool init --config .config/tool.yaml`

Test plan

`TestRunHook_SetsEnvVars` — all 4 env vars set correctly
`TestRunHook_EmptyIsNoOp` — empty string is a no-op
`TestRunHook_NonZeroExitReturnsError` — failed hooks return error
`TestRunHook_RunsInDir` — hook executes in specified directory
`TestBinaryListMarshalYAML_OnPostRoundTrip` — b.yaml round-trip
`TestAddToConfig_WithOnPost` — `--on-post` flag persists to config
`go test ./...` — all 39 packages pass
E2E: `b install --add --on-post 'echo HOOK: ${B_NAME}' github.com/arg-sh/argsh` → hook runs, onPost saved to b.yaml

🤖 Generated with Claude Code

Adds a per-binary post-install/update hook: a shell command that runs after a successful download, receiving B_EVENT (install|update), B_NAME, B_VERSION, and B_FILE as env vars. Non-zero exit is surfaced as a warning, not a fatal error. Skipped when the binary didn't change. b.yaml: binaries: github.com/arg-sh/argsh: onPost: argsh builtin ${B_EVENT} CLI: b install --add github.com/arg-sh/argsh --on-post 'argsh builtin ${B_EVENT}' Implementation: - LocalBinary gains OnPost (yaml:"onPost") — round-trips via BinaryList Marshal/Unmarshal. - managedKey updated so SaveConfig preserves the field but can also remove it when the user deletes it from config. - RunHook helper in pkg/binary/hook.go — exec.Command with the four B_ env vars set, runs in the project root directory. - install.go / update.go call RunHook after a successful EnsureBinary / DownloadBinary, with event="install" or "update" respectively. - --on-post flag on 'b install' feeds into addToConfig. Tests: - TestRunHook_{SetsEnvVars,EmptyIsNoOp,NonZeroExitReturnsError,RunsInDir} - TestBinaryListMarshalYAML_OnPostRoundTrip - TestAddToConfig_WithOnPost Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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Pull request overview

This PR introduces a per-binary onPost hook that runs a user-provided shell command after binary install/update, and persists that hook via b.yaml/--add so it can be replayed on subsequent runs.

Changes:

Add onPost to the binary config model and YAML merge/round-trip behavior.
Execute onPost after b install / b update operations.
Add unit tests covering hook env vars + YAML/config persistence.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
pkg/state/yamlmerge.go	Treat `binaries.<name>.onPost` as a managed key when rewriting YAML.
pkg/state/types.go	Emit `onPost` during `BinaryList.MarshalYAML`.
pkg/state/types_test.go	Add YAML round-trip test for `onPost`.
pkg/cli/shared.go	Plumb `OnPost` from config into resolved `binary.Binary`.
pkg/cli/install.go	Add `--on-post` flag, persist it with `--add`, and run hook post-install.
pkg/cli/update.go	Run hook post-update.
pkg/cli/cli_extra_test.go	Test that `--on-post` persists to config via `addToConfig`.
pkg/binary/types.go	Add `OnPost` fields to `Binary`/`LocalBinary` types and document semantics.
pkg/binary/hook.go	Introduce `RunHook` helper that sets `B_*` env vars and executes a shell command.
pkg/binary/hook_test.go	Add tests for env vars, no-op behavior, non-zero exit, and working directory.

Copilot review round 1: 1. RunHook signature changed from *os.File to io.Writer so callers can route through the CLI's IO streams (respecting --quiet, output capture). nil defaults to io.Discard. Added docstring noting hooks are POSIX-only (sh -c), consistent with existing env hooks. 2. install.go: track wasMissing before EnsureBinary(false) so the hook only fires when a download actually happened. Force mode always counts as downloaded. Streams routed through o.IO. 3. update.go: track 'downloaded' per branch — DownloadBinary branches set it on err==nil; EnsureBinary compares pre/post SHA to detect whether the file actually changed. Hook gated behind '!o.effectiveDryRun()' for --dry-run/--plan-json respect. Streams routed through o.IO. 4. Types.go docstring updated to match actual guarantees: only fires when on-disk binary changed, not on no-op skip or dry-run. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

macOS /var → /private/var symlink causes t.TempDir() to return the unresolved path while pwd in the hook resolves it. Use filepath.EvalSymlinks + strings.TrimSpace for the comparison. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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