feat(cli): support configuration via PINO_PRETTY_* environment variables

bin.js

@@ -73,8 +73,9 @@ if (cmd.h || cmd.help) {
   // Remove default values
   opts = filter(opts, value => value !== DEFAULT_VALUE)
   const config = loadConfig(opts.config)
-  // Override config with cli options
-  opts = Object.assign({}, config, opts)
+  const envConfig = loadEnvConfig()
+  // Priority: CLI flags > config file > env vars
+  opts = Object.assign({}, envConfig, config, opts)
   // set defaults
   opts.errorLikeObjectKeys = opts.errorLikeObjectKeys || 'err,error'
   opts.errorProps = opts.errorProps || ''
@@ -101,6 +102,56 @@ if (cmd.h || cmd.help) {
     return result.data
   }
 
+  /**
+   * Load pino-pretty configuration from environment variables.
+   * All options use the `PINO_PRETTY_` prefix and SCREAMING_SNAKE_CASE naming.
+   * For example: `--singleLine` → `PINO_PRETTY_SINGLE_LINE=true`
+   * Boolean options accept: `true`, `1`, `false`, `0` (case-insensitive).
+   * @returns {object}
+   */
+  function loadEnvConfig () {
+    const envMap = {
+      PINO_PRETTY_COLORIZE: { key: 'colorize', type: 'boolean' },
+      PINO_PRETTY_CRLF: { key: 'crlf', type: 'boolean' },
+      PINO_PRETTY_ERROR_PROPS: { key: 'errorProps', type: 'string' },
+      PINO_PRETTY_LEVEL_FIRST: { key: 'levelFirst', type: 'boolean' },
+      PINO_PRETTY_MINIMUM_LEVEL: { key: 'minimumLevel', type: 'string' },
+      PINO_PRETTY_CUSTOM_LEVELS: { key: 'customLevels', type: 'string' },
+      PINO_PRETTY_CUSTOM_COLORS: { key: 'customColors', type: 'string' },
+      PINO_PRETTY_USE_ONLY_CUSTOM_PROPS: { key: 'useOnlyCustomProps', type: 'boolean' },
+      PINO_PRETTY_ERROR_LIKE_OBJECT_KEYS: { key: 'errorLikeObjectKeys', type: 'string' },
+      PINO_PRETTY_MESSAGE_KEY: { key: 'messageKey', type: 'string' },
+      PINO_PRETTY_LEVEL_KEY: { key: 'levelKey', type: 'string' },
+      PINO_PRETTY_LEVEL_LABEL: { key: 'levelLabel', type: 'string' },
+      PINO_PRETTY_MESSAGE_FORMAT: { key: 'messageFormat', type: 'string' },
+      PINO_PRETTY_TIMESTAMP_KEY: { key: 'timestampKey', type: 'string' },
+      PINO_PRETTY_TRANSLATE_TIME: { key: 'translateTime', type: 'string' },
+      PINO_PRETTY_IGNORE: { key: 'ignore', type: 'string' },
+      PINO_PRETTY_INCLUDE: { key: 'include', type: 'string' },
+      PINO_PRETTY_HIDE_OBJECT: { key: 'hideObject', type: 'boolean' },
+      PINO_PRETTY_SINGLE_LINE: { key: 'singleLine', type: 'boolean' }
+    }
+
+    const result = {}
+    for (const [envKey, { key, type }] of Object.entries(envMap)) {
+      const value = process.env[envKey]
+      if (value === undefined || value === '') continue
+
+      if (type === 'boolean') {
+        const lower = value.toLowerCase()
+        if (lower === 'true' || lower === '1') {
+          result[key] = true
+        } else if (lower === 'false' || lower === '0') {
+          result[key] = false
+        }
+        // Invalid boolean values are silently ignored
+      } else {
+        result[key] = value
+      }
+    }
+    return result
+  }
+
   function filter (obj, cb) {
     return Object.keys(obj).reduce((acc, key) => {
       const value = obj[key]

test/cli-env.test.js

@@ -0,0 +1,114 @@
+'use strict'
+
+process.env.TZ = 'UTC'
+
+const path = require('node:path')
+const { spawn } = require('node:child_process')
+const { describe, test } = require('node:test')
+const { once } = require('./helper')
+
+const bin = require.resolve(path.join(__dirname, '..', 'bin.js'))
+const logLine = '{"level":30,"time":1522431328992,"msg":"hello world","pid":42,"hostname":"foo"}\n'
+const baseEnv = { TERM: 'dumb', TZ: 'UTC' }
+const formattedEpoch = '17:35:28.992'
+
+describe('cli env vars', () => {
+  test('PINO_PRETTY_LEVEL_FIRST=true flips level and time', async (t) => {
+    t.plan(1)
+    const env = { ...baseEnv, PINO_PRETTY_LEVEL_FIRST: 'true' }
+    const child = spawn(process.argv[0], [bin], { env })
+    child.on('error', t.assert.fail)
+    const endPromise = once(child.stdout, 'data', (data) => {
+      t.assert.strictEqual(data.toString(), `INFO [${formattedEpoch}] (42): hello world\n`)
+    })
+    child.stdin.write(logLine)
+    await endPromise
+    t.after(() => child.kill())
+  })
+
+  test('PINO_PRETTY_LEVEL_FIRST=1 flips level and time', async (t) => {
+    t.plan(1)
+    const env = { ...baseEnv, PINO_PRETTY_LEVEL_FIRST: '1' }
+    const child = spawn(process.argv[0], [bin], { env })
+    child.on('error', t.assert.fail)
+    const endPromise = once(child.stdout, 'data', (data) => {
+      t.assert.strictEqual(data.toString(), `INFO [${formattedEpoch}] (42): hello world\n`)
+    })
+    child.stdin.write(logLine)
+    await endPromise
+    t.after(() => child.kill())
+  })
+
+  test('PINO_PRETTY_SINGLE_LINE=true prints all on one line', async (t) => {
+    t.plan(1)
+    const multiKeyLog = '{"level":30,"time":1522431328992,"msg":"hello","pid":42,"hostname":"foo","extra":"value"}\n'
+    const env = { ...baseEnv, PINO_PRETTY_SINGLE_LINE: 'true' }
+    const child = spawn(process.argv[0], [bin], { env })
+    child.on('error', t.assert.fail)
+    const endPromise = once(child.stdout, 'data', (data) => {
+      // In single line mode the extra fields appear inline, not on separate lines
+      const output = data.toString()
+      t.assert.ok(!output.includes('\n    '), 'should not have indented extra fields')
+    })
+    child.stdin.write(multiKeyLog)
+    await endPromise
+    t.after(() => child.kill())
+  })
+
+  test('PINO_PRETTY_IGNORE=pid,hostname removes those keys', async (t) => {
+    t.plan(1)
+    const env = { ...baseEnv, PINO_PRETTY_IGNORE: 'pid,hostname' }
+    const child = spawn(process.argv[0], [bin], { env })
+    child.on('error', t.assert.fail)
+    const endPromise = once(child.stdout, 'data', (data) => {
+      t.assert.strictEqual(data.toString(), `[${formattedEpoch}] INFO: hello world\n`)
+    })
+    child.stdin.write(logLine)
+    await endPromise
+    t.after(() => child.kill())
+  })
+
+  test('PINO_PRETTY_MESSAGE_KEY overrides default message key', async (t) => {
+    t.plan(1)
+    const customLog = '{"level":30,"time":1522431328992,"message":"custom key msg","pid":42,"hostname":"foo"}\n'
+    const env = { ...baseEnv, PINO_PRETTY_MESSAGE_KEY: 'message' }
+    const child = spawn(process.argv[0], [bin], { env })
+    child.on('error', t.assert.fail)
+    const endPromise = once(child.stdout, 'data', (data) => {
+      t.assert.ok(data.toString().includes('custom key msg'))
+    })
+    child.stdin.write(customLog)
+    await endPromise
+    t.after(() => child.kill())
+  })
+
+  test('CLI flag overrides env var (CLI wins)', async (t) => {
+    t.plan(1)
+    // env says level-first=true, but CLI does not pass it => CLI default should win
+    // Since the default is no levelFirst, output should show time first
+    const env = { ...baseEnv, PINO_PRETTY_LEVEL_FIRST: 'false' }
+    const child = spawn(process.argv[0], [bin, '--levelFirst'], { env })
+    child.on('error', t.assert.fail)
+    const endPromise = once(child.stdout, 'data', (data) => {
+      // CLI flag wins: level appears first
+      t.assert.strictEqual(data.toString(), `INFO [${formattedEpoch}] (42): hello world\n`)
+    })
+    child.stdin.write(logLine)
+    await endPromise
+    t.after(() => child.kill())
+  })
+
+  test('invalid PINO_PRETTY_LEVEL_FIRST value is silently ignored', async (t) => {
+    t.plan(1)
+    const env = { ...baseEnv, PINO_PRETTY_LEVEL_FIRST: 'yes' }
+    const child = spawn(process.argv[0], [bin], { env })
+    child.on('error', t.assert.fail)
+    const endPromise = once(child.stdout, 'data', (data) => {
+      // Default output: time first
+      t.assert.strictEqual(data.toString(), `[${formattedEpoch}] INFO (42): hello world\n`)
+    })
+    child.stdin.write(logLine)
+    await endPromise
+    t.after(() => child.kill())
+  })
+})