Resolve config items on demand so untaken references are never resolved

Open
  • Is something wrong?
#1,158 1 comment 0 reactions 0 assignees View on GitHub

Maintainers usually reply within 1 day

Nobody has claimed this yet.

Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Quiet
Tech stack
typescript
Domain
backend

Research direction

Start by reading the resolver implementation around ConfigItem.resolve(), getDepValue, and resolveEnvValues, then trace the --filter and @import(..., enabled=...) paths. The issue names no file or test, so locate those entry points and inspect tests for conditional references, dependency errors, cache attribution, side effect ordering, and sensitive value checks. Done means requested keys resolve dependencies on demand while static cycle detection and the listed partial load behaviors remain correct.

Written by the indexing model from the issue text.

Description

Follow-up from #1153 (and() / or()).

Problem

Resolver functions short-circuit their own nested function calls (and(false, op(...)) never calls op()), but not item references. and(false, $EXPENSIVE) and if(false, $A, $B) still resolve EXPENSIVE / A, because resolveEnvValues schedules each item only after every key in its dependencyKeys has resolved, and ref() just reads the already-resolved value.

In a full load this costs nothing, since every item resolves anyway. It matters for partial loads, where the unused dependency is otherwise never needed:

  • --filter: matched items plus their transitive deps
  • early-resolved @import(..., enabled=...) conditions

Proposal: resolve items on demand

Switch the graph from a push scheduler to pull-based resolution:

  • ConfigItem.resolve() memoizes its in-flight promise so concurrent readers share one run (no double op() calls)
  • getDepValue (only used by ref()) becomes async and awaits depItem.resolve() instead of throwing when the dep is unresolved
  • resolveEnvValues becomes a Promise.all over the requested keys; deps are pulled in as they are read, still in parallel
  • earlyResolve() and the transitive-dep expansion used by --filter / @import(enabled=...) go away; those paths resolve just the keys they need
  • keep static dep collection for cycle detection, type generation, etc. Static cycles stay an error, so a runtime deadlock is impossible (runtime reads are a subset of static edges)

This makes if(), ifs(), remap(), and(), or() and fallback() lazy for references without marking conditional arg positions per function.

Things to handle

  • "Dependency X is invalid" would only apply when X is actually read, not when it sits in an untaken branch. Arguably more correct, but error output and some tests change
  • each on-demand resolve needs its own resolution context (current item, cache store) so cache hits are attributed correctly
  • ordering of side effects (exec() etc.) may shift; tests relying on order (e.g. the increment test resolver) may need updates
  • partial loads leave more items unresolved; audit code that assumes all deps of a resolved item are resolved (e.g. checkForSensitiveValuesInsideNonSensitiveOnes)

Related

  • #1147 (lazy plugin functions in untaken branches) overlaps, though it also needs the unknown-function check deferred, which this does not cover
Dominant language
TypeScript
Stars
4.9k
Forks
140
Avg merge
2d 3h
Merged PRs (30d)
35

Getting set up

This project ships no dev container, Dockerfile or contributing guide, so setting up is up to you: start from its README, and see our first-contribution guide for the general steps.

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from dmno-dev/varlock

All issues in dmno-dev/varlock

Similar issues

More TypeScript issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.