feat: add pklr as opt-in pkl backend by jdx · Pull Request #768 · jdx/hk

jdx · 2026-03-23T21:40:45Z

Summary

Add pklr (v0.2) as a dependency — a pure Rust pkl evaluator
When HK_PKL_BACKEND=pklr is set, use pklr instead of the pkl CLI for both config evaluation and import analysis
Default behavior unchanged (pkl CLI)

This eliminates the pkl binary dependency when opted in. Useful for environments where installing the pkl CLI is difficult.

Test plan

cargo check passes
HK_PKL_BACKEND=pklr hk run check on a project with hk.pkl
Verify default behavior (without env var) is unchanged

Note

Medium Risk
Default behavior stays on the pkl CLI, but this adds a new evaluation/import-analysis path with its own async runtime handling; differences in pkl feature support or import resolution could affect config loading/caching when opted in.

Overview
Adds pklr as a dependency and introduces HK_PKL_BACKEND=pklr to switch .pkl config evaluation and import analysis from shelling out to the pkl CLI to using the built-in Rust evaluator (run_pklr, pklr::eval_to_json, pklr::analyze_imports).

Updates docs to describe the new experimental backend and how to enable it, and adds a bats test (test/pklr_backend.bats) to verify basic evaluation and hk validate work under the pklr backend.

^{Written by Cursor Bugbot for commit be28735. This will update automatically on new commits. Configure here.}

Set `HK_PKL_BACKEND=pklr` to use the built-in Rust pkl evaluator instead of shelling out to the pkl CLI. This eliminates the pkl binary dependency when enabled. Both `eval` and `analyze_imports` are routed through pklr when the env var is set. The default behavior (using the pkl CLI) is unchanged. Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

gemini-code-assist · 2026-03-23T21:40:48Z

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greptile-apps · 2026-03-23T21:42:30Z

Greptile Summary

This PR adds pklr (a pure-Rust pkl evaluator) as an opt-in backend for config evaluation and import analysis, controlled by HK_PKL_BACKEND=pklr. The core path in Config::read and Config::analyze_imports correctly branches on the env var, and run_pklr properly bridges async work into the synchronous call stack using block_in_place when inside the existing multi-thread tokio runtime.

Key changes:

pklr = "0.2" added to Cargo.toml; HK_PKL_BACKEND lazy static added to env.rs
Config::read dispatches to run_pklr when backend is pklr, otherwise uses the existing run_pkl CLI path
Config::analyze_imports similarly branches on the backend
apply_hkrc does not respect HK_PKL_BACKEND and always calls run_pkl — users who set the env var to eliminate the pkl CLI dependency will still see a failure if they have any hkrc/global config pkl file
pklr::analyze_imports is called without the async-runtime bridging that run_pklr carefully provides for eval_to_json; if pklr performs async work internally, this will panic inside the main tokio runtime
Documentation and bats tests are clean and well-written

Confidence Score: 3/5

Safe to merge for default users (pkl CLI path unchanged), but the pklr backend is incomplete and will silently break for any user with a global hkrc config file.
The default pkl CLI path is entirely untouched. However, the pklr backend has a clear gap: apply_hkrc always calls run_pkl, meaning the pklr backend does not fully eliminate the pkl CLI dependency as advertised. There is also an async-bridging inconsistency in analyze_imports that could cause runtime panics depending on pklr's internal implementation. Both issues are confined to the new opt-in path and do not affect the default behavior, but they do mean the new feature doesn't reliably deliver on its core promise.
src/config.rs — specifically the apply_hkrc function and the pklr::analyze_imports call site.

Important Files Changed

Filename	Overview
src/config.rs	Adds `run_pklr` helper and two pklr-gated branches in `read` and `analyze_imports`; however, `apply_hkrc` hardcodes `run_pkl` and will ignore `HK_PKL_BACKEND`, and `pklr::analyze_imports` is called without the same async bridging used for `eval_to_json`.
src/env.rs	Adds `HK_PKL_BACKEND` as a simple `Option<String>` lazy static; straightforward addition with no issues.
Cargo.toml	Adds `pklr = "0.2"` as an unconditional dependency; prior review already flagged the optional-feature concern.
test/pklr_backend.bats	New bats integration tests for pklr backend; covers basic evaluation and validate — reasonable coverage for a first pass.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Config::get] --> B[load_project_config]
    B --> C[load_config_cached]
    C --> D{is pkl file?}
    D -- yes --> E[analyze_imports]
    D -- no --> H[Config::read]
    E --> F{HK_PKL_BACKEND == pklr?}
    F -- yes --> G[pklr::analyze_imports\nno async bridging]
    F -- no --> I[run_pkl analyze imports]
    C --> H
    H --> J{ext == pkl?}
    J -- yes --> K{HK_PKL_BACKEND == pklr?}
    K -- yes --> L[run_pklr\nblock_in_place / new runtime]
    K -- no --> M[run_pkl eval]
    J -- no --> N[toml/yaml/json parser]
    C --> O[apply_hkrc]
    O --> P[run_pkl eval\nALWAYS - ignores HK_PKL_BACKEND]
    style P fill:#f88,stroke:#c00
    style G fill:#ffa,stroke:#aa0

Comments Outside Diff (1)

src/config.rs, line 297 (link)

apply_hkrc ignores HK_PKL_BACKEND

apply_hkrc always calls run_pkl for hkrc files regardless of the backend setting. If a user sets HK_PKL_BACKEND=pklr specifically to avoid the pkl CLI requirement, but they have a ~/.config/hk/config.pkl, .hkrc.pkl, or ~/.hkrc.pkl, this code will still invoke the pkl CLI (and fail with "install pkl cli to use pkl config files" if it isn't present). This defeats the whole point of the feature for users with a global config.

_{Reviews (3): Last reviewed commit: "docs: document pklr backend, update pkl ..." | Re-trigger Greptile}

greptile-apps · 2026-03-23T21:42:37Z

 libc               = "0.2"
 log                = "0.4"
 once_cell          = "1"
+pklr               = "0.2"


pklr is a hard dependency, not opt-in

The PR description calls pklr an "opt-in" backend, but it is added as an unconditional dependency. This increases binary size and compile time for all users, including those who never use pkl files or never set HK_PKL_BACKEND. Consider making it a Cargo feature:

pklr = { version = "0.2", optional = true }

Then gate the pklr code paths with #[cfg(feature = "pklr")] in config.rs. This keeps the default binary lean and makes "opt-in" accurate in both the runtime and build-time senses.

- Getting started: pkl CLI no longer required when HK_PKL_BACKEND=pklr - pkl introduction: document pklr as built-in evaluator, note it will eventually become the default - Configuration: mention pklr option - Add bats test for pklr backend Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

greptile-apps · 2026-03-23T22:03:27Z

+            return pklr::analyze_imports(path)
+                .map(|v| v.into_iter().collect())
+                .map_err(|e| eyre::eyre!("{e}"));


pklr::analyze_imports called without async runtime bridging

pklr::eval_to_json is async and requires the run_pklr wrapper to safely bridge into sync code (handling both existing multi-thread runtimes via block_in_place and the no-runtime case). pklr::analyze_imports is called here without any such bridging.

Since pklr depends on tokio and reqwest (for downloading package imports over HTTP), analyze_imports likely needs async I/O internally. If it creates its own tokio::runtime::Runtime internally while already running inside the main #[tokio::main] multi-thread runtime, it will panic with "Cannot start a runtime from within a runtime."

If pklr::analyze_imports is also an async function (or wraps async work), it should be called through run_pklr or an equivalent wrapper:

if env::HK_PKL_BACKEND.as_deref() == Some("pklr") { let paths = run_pklr_analyze_imports(path)?; return Ok(paths.into_iter().collect()); }

It is worth verifying the exact signature and internal runtime handling of pklr::analyze_imports before shipping.

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cursor · 2026-03-24T10:04:24Z

        .filter(|s| !s.is_empty())
 }

+fn run_pklr<T: DeserializeOwned>(path: &Path) -> Result<T> {


hkrc evaluation ignores pklr backend setting

High Severity

The apply_hkrc method always calls run_pkl (the CLI-based evaluator) to parse hkrc pkl files, even when HK_PKL_BACKEND=pklr is set. This means users who opt in to the pklr backend to avoid needing the pkl CLI will still fail if they have an hkrc config file (e.g., ~/.config/hk/config.pkl). The backend check that was added to read and analyze_imports is missing from this code path.

@hituzi-no-sippo

This MR contains the following updates: | Package | Update | Change | |---|---|---| | [hk](https://github.com/jdx/hk) | minor | `1.39.0` → `1.40.0` | MR created with the help of [el-capitano/tools/renovate-bot](https://gitlab.com/el-capitano/tools/renovate-bot). **Proposed changes to behavior should be submitted there as MRs.** --- ### Release Notes <details> <summary>jdx/hk (hk)</summary> ### [`v1.40.0`](https://github.com/jdx/hk/blob/HEAD/CHANGELOG.md#1400---2026-04-01) [Compare Source](jdx/hk@v1.39.0...v1.40.0) ##### 🚀 Features - **(betterleaks)** add betterleaks config to hk builtin config by [@hituzi-no-sippo](https://github.com/hituzi-no-sippo) in [#750](jdx/hk#750) - **(builtins)** add google-java-format to builtins by [@timothysparg](https://github.com/timothysparg) in [#777](jdx/hk#777) - **(builtins)** add dclint to builtins by [@timothysparg](https://github.com/timothysparg) in [#779](jdx/hk#779) - **(config)** set default value for exclude to List() by [@timothysparg](https://github.com/timothysparg) in [#781](jdx/hk#781) - **(core)** add required field to prevent unconfigured steps from running by [@timothysparg](https://github.com/timothysparg) in [#785](jdx/hk#785) - **(gitleaks)** add gitleaks config to hk builtin config by [@hituzi-no-sippo](https://github.com/hituzi-no-sippo) in [#749](jdx/hk#749) - **(mdschema)** add mdschema config to hk builtin config by [@hituzi-no-sippo](https://github.com/hituzi-no-sippo) in [#748](jdx/hk#748) - **(pkl)** add pklr as opt-in pkl backend by [@jdx](https://github.com/jdx) in [#769](jdx/hk#769) - add pklr as opt-in pkl backend by [@jdx](https://github.com/jdx) in [#768](jdx/hk#768) ##### 🐛 Bug Fixes - **(docs)** replace invalid /latest/ pkl package URIs with versioned format by [@jdx](https://github.com/jdx) in [#770](jdx/hk#770) - **(stage)** do not stage pre-existing untracked files by [@jdx](https://github.com/jdx) in [#788](jdx/hk#788) ##### 📚 Documentation - add benchmarks page and reproducible benchmark suite by [@jdx](https://github.com/jdx) in [#766](jdx/hk#766) - add recommended setup section to mise integration by [@timothysparg](https://github.com/timothysparg) in [#780](jdx/hk#780) ##### 📦️ Dependency Updates - lock file maintenance by [@renovate\[bot\]](https://github.com/renovate\[bot]) in [#762](jdx/hk#762) - update rust crate pklr to 0.4 by [@renovate\[bot\]](https://github.com/renovate\[bot]) in [#776](jdx/hk#776) - update apple-actions/import-codesign-certs digest to [`fe74d46`](jdx/hk@fe74d46) by [@renovate\[bot\]](https://github.com/renovate\[bot]) in [#774](jdx/hk#774) - update anthropics/claude-code-action digest to [`094bd24`](jdx/hk@094bd24) by [@renovate\[bot\]](https://github.com/renovate\[bot]) in [#773](jdx/hk#773) - update taiki-e/upload-rust-binary-action digest to [`0e34102`](jdx/hk@0e34102) by [@renovate\[bot\]](https://github.com/renovate\[bot]) in [#775](jdx/hk#775) - bump usage to 3.2.0 and pkl to 0.31.1, add windows platforms by [@jdx](https://github.com/jdx) in [#787](jdx/hk#787) - lock file maintenance by [@renovate\[bot\]](https://github.com/renovate\[bot]) in [#786](jdx/hk#786) ##### New Contributors - [@timothysparg](https://github.com/timothysparg) made their first contribution in [#781](jdx/hk#781) </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever MR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this MR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this MR, check this box --- This MR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).

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jdx deleted the feat/pklr-backend branch March 23, 2026 22:02

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chore: release v1.40.0 #763

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feat: add pklr as opt-in pkl backend#768

feat: add pklr as opt-in pkl backend#768
jdx merged 3 commits intomainfrom
feat/pklr-backend

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Confidence Score: 3/5

Important Files Changed

Flowchart

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hkrc evaluation ignores pklr backend setting

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