effect-analyzer

The Standout Features

Live Browser Playground

Paste Effect code into a static in-browser playground and get a rendered railway diagram immediately.

Open the playground

Interactive HTML Export

Generate a shareable analysis page with search, filters, path explorer, themes, and embedded IR.

Open the HTML demo

These two features are what make the library easy to share: one lets people try it instantly, the other turns analysis into a linkable artifact.

See It in Action

Example fixture: packages/effect-analyzer/src/__fixtures__/docs/transfer-workflow.ts

export const transferWorkflow = (
  fromAccountId: string,
  toAccountId: string,
  amount: number,
) =>
  Effect.gen(function* () {
    const accounts = yield* AccountService
    const audit = yield* AuditLog

    const balance = yield* accounts.getBalance(fromAccountId)
    if (balance < amount) {
      return yield* Effect.fail(new InsufficientFundsError(balance, amount))
    }

    yield* accounts.debit(fromAccountId, amount)
    yield* accounts.credit(toAccountId, amount)
    yield* audit.record(`Transferred ${amount} from ${fromAccountId} to ${toAccountId}`)
  })

$ npx effect-analyze ./src/__fixtures__/docs/transfer-workflow.ts --format explain

transferWorkflow (generator):
  1. Yields accounts <- AccountService
  2. Yields audit <- AuditLog
  3. Yields balance <- accounts.getBalance
  4. If balance < amount:
    Returns:
      Calls fail - constructor
  5. Calls accounts.debit
  6. Calls accounts.credit
  7. Calls audit.record

  Services required: AccountService, AuditLog
  Error paths: AccountNotFoundError, InsufficientFundsError
  Concurrency: sequential (no parallelism)

flowchart LR
  prog["transferWorkflow"]

  svc_AccountService{{"AccountService"}}
  prog -->|requires| svc_AccountService
  svc_AuditLog{{"AuditLog"}}
  prog -->|requires| svc_AuditLog

Features

Static Analysis

Analyze Effect programs without execution. Extracts generators, pipes, services, layers, error handlers, and control flow.

Mermaid Diagrams

Auto-generate flowcharts, railway diagrams, service maps, error flows, concurrency views, and more.

Complexity Metrics

Calculate cyclomatic complexity, cognitive complexity, path counts, nesting depth, and parallel breadth.

Semantic Diff

Compare two versions of an Effect program to see what changed - steps added, removed, or modified.

Start With The Visuals

• Try the live playground to paste code and see the railway diagram in the browser.
• Open the interactive HTML demo to see the exported viewer embedded directly in the docs.
• Read the t3code case study to see Mermaid diff output used on a real codebase.

Quick Start

# Install
npm install effect-analyzer

# Analyze a file
npx effect-analyze ./src/my-program.ts

# Generate a railway diagram
npx effect-analyze ./src/my-program.ts --format mermaid-railway

# Compare versions
npx effect-analyze HEAD:program.ts program.ts --diff