Your CLI's completion should know what options you've already typed
Consider Git's -C option:
git -C /path/to/repo checkout <TAB>
When you hit Tab, Git completes branch names from /path/to/repo, not yourcurrent directory. The completion is context-aware—it depends on the value ofanother option.
Most CLI parsers can't do this. They treat each option in isolation, socompletion for --branch has no way of knowing the --repo value. You end upwith two unpleasant choices: either show completions for all possiblebranches across all repositories (useless), or give up on completion entirelyfor these options.
Optique 0.10.0 introduces a dependency system that solves this problem whilepreserving full type safety.
Static dependencies with or()
Optique already handles certain kinds of dependent options via the or()combinator:
import { flag, object, option, or, string } from "@optique/core";const outputOptions = or( object({ json: flag("--json"), pretty: flag("--pretty"), }), object({ csv: flag("--csv"), delimiter: option("--delimiter", string()), }),);
TypeScript knows that if json is true, you'll have a pretty field, and ifcsv is true, you'll have a delimiter field. The parser enforces this atruntime, and shell completion will suggest --pretty only when --json ispresent.
This works well when the valid combinations are known at definition time. Butit can't handle cases where valid values depend on runtime input—likebranch names that vary by repository.
Runtime dependencies
Common scenarios include:
A deployment CLI where --environment affects which services are available
A database tool where --connection affects which tables can be completed
A cloud CLI where --project affects which resources are shown
In each case, you can't know the valid values until you know what the usertyped for the dependency option. Optique 0.10.0 introduces dependency() andderive() to handle exactly this.
The dependency system
The core idea is simple: mark one option as a dependency source, then createderived parsers that use its value.
import { choice, dependency, message, object, option, string,} from "@optique/core";function getRefsFromRepo(repoPath: string): string[] { // In real code, this would read from the Git repository return ["main", "develop", "feature/login"];}// Mark as a dependency sourceconst repoParser = dependency(string());// Create a derived parserconst refParser = repoParser.derive({ metavar: "REF", factory: (repoPath) => { const refs = getRefsFromRepo(repoPath); return choice(refs); }, defaultValue: () => ".",});const parser = object({ repo: option("--repo", repoParser, { description: message`Path to the repository`, }), ref: option("--ref", refParser, { description: message`Git reference`, }),});
The factory function is where the dependency gets resolved. It receives theactual value the user provided for --repo and returns a parser that validatesagainst refs from that specific repository.
Under the hood, Optique uses a three-phase parsing strategy:
Parse all options in a first pass, collecting dependency values
Call factory functions with the collected values to create concrete parsers
Re-parse derived options using those dynamically created parsers
This means both validation and completion work correctly—if the user hasalready typed --repo /some/path, the --ref completion will show refs fromthat path.
Repository-aware completion with @optique/git
The @optique/git package provides async value parsers that read from Gitrepositories. Combined with the dependency system, you can build CLIs withrepository-aware completion:
import { command, dependency, message, object, option, string,} from "@optique/core";import { gitBranch } from "@optique/git";const repoParser = dependency(string());const branchParser = repoParser.deriveAsync({ metavar: "BRANCH", factory: (repoPath) => gitBranch({ dir: repoPath }), defaultValue: () => ".",});const checkout = command( "checkout", object({ repo: option("--repo", repoParser, { description: message`Path to the repository`, }), branch: option("--branch", branchParser, { description: message`Branch to checkout`, }), }),);
Now when you type my-cli checkout --repo /path/to/project --branch <TAB>, thecompletion will show branches from /path/to/project. The defaultValue of"." means that if --repo isn't specified, it falls back to the currentdirectory.
Multiple dependencies
Sometimes a parser needs values from multiple options. The deriveFrom()function handles this:
import { choice, dependency, deriveFrom, message, object, option,} from "@optique/core";function getAvailableServices(env: string, region: string): string[] { return [`${env}-api-${region}`, `${env}-web-${region}`];}const envParser = dependency(choice(["dev", "staging", "prod"] as const));const regionParser = dependency(choice(["us-east", "eu-west"] as const));const serviceParser = deriveFrom({ dependencies: [envParser, regionParser] as const, metavar: "SERVICE", factory: (env, region) => { const services = getAvailableServices(env, region); return choice(services); }, defaultValues: () => ["dev", "us-east"] as const,});const parser = object({ env: option("--env", envParser, { description: message`Deployment environment`, }), region: option("--region", regionParser, { description: message`Cloud region`, }), service: option("--service", serviceParser, { description: message`Service to deploy`, }),});
The factory receives values in the same order as the dependency array. Ifsome dependencies aren't provided, Optique uses the defaultValues.
Async support
Real-world dependency resolution often involves I/O—reading from Gitrepositories, querying APIs, accessing databases. Optique provides asyncvariants for these cases:
import { dependency, string } from "@optique/core";import { gitBranch } from "@optique/git";const repoParser = dependency(string());const branchParser = repoParser.deriveAsync({ metavar: "BRANCH", factory: (repoPath) => gitBranch({ dir: repoPath }), defaultValue: () => ".",});
The @optique/git package uses isomorphic-git under the hood, sogitBranch(), gitTag(), and gitRef() all work in both Node.js and Deno.
There's also deriveSync() for when you need to be explicit about synchronousbehavior, and deriveFromAsync() for multiple async dependencies.
Wrapping up
The dependency system lets you build CLIs where options are aware of eachother—not just for validation, but for shell completion too. You get typesafety throughout: TypeScript knows the relationship between your dependencysources and derived parsers, and invalid combinations are caught at compiletime.
This is particularly useful for tools that interact with external systems wherethe set of valid values isn't known until runtime. Git repositories, cloudproviders, databases, container registries—anywhere the completion choicesdepend on context the user has already provided.
This feature will be available in Optique 0.10.0. To try the pre-release:
deno add jsr:@optique/[email protected]
Or with npm:
npm install @optique/[email protected]
See the documentation for more details.
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洪 民憙 (Hong Minhee)