JavaScript/TypeScript Stack - RTK (Rust Token Killer)

Overview

RTK provides comprehensive support for the modern JavaScript/TypeScript ecosystem. Achieve 70-94% token savings through:

JSON parsing: Structured output from linters and compilers
Error grouping: Group by file, rule, or error code
Failures only: Show only failing tests and checks
Package manager detection: Auto-detects pnpm/npm/yarn/npx

Supported Tools

ESLint

Linting with rule grouping (84% savings)

TypeScript

Compiler errors grouped by file (83% savings)

Next.js

Build/dev with route metrics (87% savings)

Prettier

Format checking (70% savings)

Vitest

Test failures only (99.5% savings)

Playwright

E2E test results (94% savings)

Prisma

Schema operations (88% savings)

rtk lint

ESLint and other linters with rule-based grouping.

Usage

rtk lint [linter] [options]

Supported Linters

eslint (default)
biome
oxc (experimental)

Examples

$ eslint .
/path/to/project/src/components/Button.tsx
  12:15  error  'React' must be in scope when using JSX  react/react-in-jsx-scope
  18:23  error  Missing semicolon                        semi
  24:5   warning  Unexpected console statement           no-console

/path/to/project/src/utils/helpers.ts
  8:10   error  'foo' is assigned a value but never used  @typescript-eslint/no-unused-vars
  15:3   error  Missing semicolon                          semi

✖ 5 problems (4 errors, 1 warning)
# 12+ lines, ~500 tokens

$ rtk lint
✗ 4 errors, 1 warning (2 files)

By rule:
  semi: 2 errors
    src/components/Button.tsx:18
    src/utils/helpers.ts:15

  react/react-in-jsx-scope: 1 error
    src/components/Button.tsx:12

  @typescript-eslint/no-unused-vars: 1 error
    src/utils/helpers.ts:8

  no-console: 1 warning
    src/components/Button.tsx:24
# 15 lines, ~80 tokens (84% savings)

Features

Rule grouping: Group violations by rule ID
Severity levels: Separate errors and warnings
File locations: Show file:line for each violation
Exit code preservation: Safe for CI/CD

Implementation

From src/lint_cmd.rs:

// Forces JSON output
cmd.arg("-f").arg("json");

// Parses EslintResult JSON array
let results: Vec<EslintResult> = serde_json::from_str(&stdout)?;

// Groups by rule_id
let mut by_rule: HashMap<String, Vec<(String, usize)>> = HashMap::new();
for result in results {
    for msg in result.messages {
        by_rule.entry(msg.rule_id)
            .or_default()
            .push((result.file_path, msg.line));
    }
}

rtk tsc

TypeScript compiler errors grouped by file.

Usage

rtk tsc [options]

Examples

$ tsc
src/components/Button.tsx(12,15): error TS2322: Type 'string' is not assignable to type 'number'.
src/components/Button.tsx(18,23): error TS2304: Cannot find name 'React'.
src/utils/helpers.ts(8,10): error TS6133: 'foo' is declared but its value is never read.
src/utils/helpers.ts(15,3): error TS1005: ';' expected.
src/api/client.ts(42,5): error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
# 5+ lines, ~300 tokens

$ rtk tsc
✗ 5 errors (3 files)

src/components/Button.tsx (2 errors)
  TS2322:12 Type 'string' is not assignable to type 'number'
  TS2304:18 Cannot find name 'React'

src/utils/helpers.ts (2 errors)
  TS6133:8 'foo' is declared but its value is never read
  TS1005:15 ';' expected

src/api/client.ts (1 error)
  TS2345:42 Argument of type 'string' is not assignable to parameter of type 'number'
# 12 lines, ~50 tokens (83% savings)

Features

File grouping: Group errors by file
Error codes: Show TypeScript error codes (TS2322, etc.)
Line numbers: Compact format TScode:line
Context preservation: Keep error messages

Implementation

From src/tsc_cmd.rs:

// Regex pattern for tsc output
static ref TSC_ERROR: Regex = Regex::new(
    r"^(.+?)\((\d+),(\d+)\):\s+(error|warning)\s+(TS\d+):\s+(.+)$"
).unwrap();

// Groups by file
let mut errors: Vec<TsError> = Vec::new();
for line in output.lines() {
    if let Some(caps) = TSC_ERROR.captures(line) {
        errors.push(TsError {
            file: caps[1].to_string(),
            line: caps[2].parse()?,
            code: caps[5].to_string(),
            message: caps[6].to_string(),
        });
    }
}

rtk next

Next.js build and dev with route metrics.

Usage

rtk next <command> [options]

Commands

build: Production build
dev: Development server
start: Start production server

Examples

$ next build
  ✔ Creating an optimized production build
  ✔ Compiled successfully
  ✔ Linting and checking validity of types
  ✔ Collecting page data
  ✔ Generating static pages (12/12)
  ✔ Collecting build traces
  ✔ Finalizing page optimization

Route (app)                              Size     First Load JS
┌ Λ /                                    142 B          87.3 kB
├ Λ /about                               156 B          87.4 kB
├ Λ /blog/[slug]                         234 B          87.5 kB
└ Λ /api/users                           0 B            87.2 kB
+ First Load JS shared by all            87.1 kB
  ├ chunks/framework-abc123.js              45.2 kB
  ├ chunks/main-def456.js                   31.8 kB
  └ other shared chunks (total)            10.1 kB
# 20+ lines, ~800 tokens

$ rtk next build
✓ Build successful (4 routes, 87.5 kB)

/                 87.3 kB
/about            87.4 kB
/blog/[slug]      87.5 kB
/api/users        87.2 kB
# 6 lines, ~100 tokens (87% savings)

Features

Route summary: Show all routes with sizes
Build metrics: Total bundle size
Error highlighting: Preserve build errors
Dev mode: Compact startup messages

rtk prettier

Format checking with files-only output.

Usage

rtk prettier [options]

Examples

$ prettier --check .
Checking formatting...
src/components/Button.tsx
src/utils/helpers.ts
src/api/client.ts
All matched files use Prettier code style!
# 5+ lines, ~200 tokens

$ rtk prettier --check .
✓ Prettier: All files formatted correctly
# 1 line, ~60 tokens (70% savings)

$ rtk prettier --check .
⚠️ 3 files need formatting:
  src/components/Button.tsx
  src/utils/helpers.ts
  src/api/client.ts
# 4 lines, ~50 tokens

Features

Pass/fail summary: Single line if all formatted
File list: Show only files needing changes
Write mode: Compact confirmation on format

rtk vitest

Vitest test runner showing failures only.

Usage

rtk vitest [command] [options]

Examples

See Testing Commands for detailed examples.

Token Savings

99.5% savings on passing tests, 90% savings on failures.

rtk playwright

Playwright E2E tests with failure grouping.

Usage

rtk playwright test [options]

Examples

$ playwright test

Running 24 tests using 4 workers
  24 passed (1.2s)

To open last HTML report run:
  npx playwright show-report
# 10+ lines, ~150 tokens (all passing)

$ rtk playwright test
✓ 24 passed (1.2s)
# 1 line, ~10 tokens (93% savings)

$ rtk playwright test
✗ 2 failed, 22 passed (1.5s)

tests/login.spec.ts
  ✗ should login with valid credentials
    Error: Timed out waiting for element

tests/checkout.spec.ts
  ✗ should complete purchase
    Error: Expected "Success" but got "Error"
# 9 lines, ~90 tokens (94% savings on 50+ line output)

Features

Failures only: Skip passing tests
Suite grouping: Group by test file
Error messages: Preserve failure details
Tee recovery: Full output saved to file

rtk prisma

Prisma CLI without ASCII art.

Usage

rtk prisma <command> [options]

Supported Commands

generate: Generate Prisma Client
migrate dev: Create and apply migration
db push: Push schema changes
studio: Open Prisma Studio (passthrough)

Examples

$ prisma generate

██████╗ ██████╗ ██╗██████╗ ███╗   ██╗ ██████╗
██╔══██╗██╔══██╗██║██╔════╝████╗ ██║██╔══██╗
Prisma schema loaded from prisma/schema.prisma
Datasource "db": PostgreSQL database "mydb"

Generating Prisma Client...
✔ Generated Prisma Client (4.8.1) to ./node_modules/@prisma/client in 823ms
# 15+ lines, ~500 tokens

$ rtk prisma generate
✓ Prisma Client generated (4.8.1) in 823ms
  Schema: prisma/schema.prisma
  Datasource: PostgreSQL (mydb)
# 3 lines, ~60 tokens (88% savings)

Features

No ASCII art: Strips Prisma logo
Essential info: Schema path, datasource, timing
Migration summaries: Compact migration output
Error preservation: Full error messages on failure

Package Manager Detection

All JavaScript tools auto-detect package manager:

// From src/utils.rs
pub fn package_manager_exec(tool: &str) -> Command {
    if has_pnpm_lock() {
        Command::new("pnpm").arg("exec").arg(tool)
    } else if has_yarn_lock() {
        Command::new("yarn").arg("exec").arg(tool)
    } else {
        Command::new("npx").arg(tool)
    }
}

Detection Order

pnpm: Check for pnpm-lock.yaml
yarn: Check for yarn.lock
npm: Default to npx

Exit Code Preservation

All commands preserve exit codes for CI/CD:

rtk lint || exit 1
rtk tsc || exit 1
rtk vitest run || exit 1
rtk playwright test || exit 1

Token Savings Summary

Command	Standard Tokens	RTK Tokens	Savings
`eslint` (5 errors)	500	80	-84%
`tsc` (5 errors)	300	50	-83%
`next build`	800	100	-87%
`prettier --check` (all pass)	200	60	-70%
`vitest run` (24 pass)	3,000	10	-99.5%
`playwright test` (2 fail, 22 pass)	1,500	90	-94%
`prisma generate`	500	60	-88%

​Overview

​Supported Tools

ESLint

TypeScript

Next.js

Prettier

Vitest

Playwright

Prisma

​rtk lint

​Usage

​Supported Linters

​Examples

​Features

​Implementation

​rtk tsc

​Usage

​Examples

​Features

​Implementation

​rtk next

​Usage

​Commands

​Examples

​Features

​rtk prettier

​Usage

​Examples

​Features

​rtk vitest

​Usage

​Examples

​Token Savings

​rtk playwright

​Usage

​Examples

​Features

​rtk prisma

​Usage

​Supported Commands

​Examples

​Features

​Package Manager Detection

​Detection Order

​Exit Code Preservation

​Token Savings Summary

​Next Steps

Python

Go

Overview

Supported Tools

rtk lint

Usage

Supported Linters

Examples

Features

Implementation

rtk tsc

Usage

Examples

Features

Implementation

rtk next

Usage

Commands

Examples

Features

rtk prettier

Usage

Examples

Features

rtk vitest

Usage

Examples

Token Savings

rtk playwright

Usage

Examples

Features

rtk prisma

Usage

Supported Commands

Examples

Features

Package Manager Detection

Detection Order

Exit Code Preservation

Token Savings Summary

Next Steps