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Best Practices

Prefer postfix methods over standalone functions​

When a combinator is available as both a standalone function and a postfix method, always prefer the postfix form. Two reasons:

  1. No type parameters. Standalone functions like getField<TObj, TField>(field) often require explicit generic arguments because TypeScript can't infer the input type without context. The postfix form action.getField("name") infers everything from the preceding action's output type — zero annotation needed.

  2. No wrapping in pipe. Standalone functions used mid-pipeline need a pipe(action, getField("name")) wrapper. Postfix chains directly: action.getField("name").

// Avoid: standalone requires type parameters and pipe wrapping
pipe(getUserProfile, getField<UserProfile, "email">("email"))

// Prefer: postfix infers types from context
getUserProfile.getField("email")

This applies to every combinator that has a postfix form: .then(), .iterate(), .map(), .flatMap(), .filter(), .collect(), .branch(), .drop(), .tag(), .flatten(), .getField(), .getIndex(), .pick(), .wrapInField(), .splitFirst(), .splitLast(), .mapErr(), .unwrapOr().

Prefer .then() over pipe()​

Postfix .then() is the primary way to chain steps. It reads naturally and infers types from context:

// Avoid
pipe(listFiles, Iterator.fromArray(), Iterator.map(processFile), Iterator.collect(), commit)

// Prefer
listFiles.iterate().map(processFile).collect().then(commit)

pipe() is available as an alternative but rarely needed — .then() chains work at any length.

Use taggedUnionSchema for handler validators​

When a handler returns a tagged union, use taggedUnionSchema(), Option.schema(), or Result.schema() instead of hand-rolling z.discriminatedUnion():

// Avoid
outputValidator: z.discriminatedUnion("kind", [
  z.object({ kind: z.literal("HasErrors"), value: z.array(errorSchema) }),
  z.object({ kind: z.literal("Clean"), value: z.null() }),
])

// Prefer
outputValidator: taggedUnionSchema({
  HasErrors: z.array(errorSchema),
  Clean: z.null(),
})

For Option and Result specifically:

outputValidator: Option.schema(z.string())     // Option<string>
outputValidator: Result.schema(z.string(), z.number())  // Result<string, number>