Add --shell-auto-fallback

README.md

@@ -30,6 +30,8 @@ By default, `<command>` will be installed prior to execution. An optional `@vers
 
 * `-c <string>` - Execute `<string>` with delayed environment variable evaluation.
 
+* `--shell-auto-fallback [shell]` - Generates shell code to override your shell's "command not found" handler with one that calls `npx`. Tries to figure out your shell, or you can pass its name (either `bash`, `fish`, or `zsh`) as an option. See below for how to install.
+
 * `-v, --version` - Show the current npx version.
 
 ## EXAMPLES
@@ -58,6 +60,30 @@ $ cat package.json
 ...webpack added to "devDependencies"
 ```
 
+## SHELL AUTO FALLBACK
+
+To install permanently, add the relevant line to your `~/.bashrc`, `~/.zshrc`, `~/.config/fish/config.fish`, or as needed. To install just for the shell session, simply run the line.
+
+Be warned that this _will_ send (almost) all your missed commands over the internet, then fetch and execute code automatically.
+
+### For Bash:
+
+```
+$ source <(npx --shell-auto-fallback bash)
+```
+
+### For Fish:
+
+```
+$ source (npx --shell-auto-fallback fish | psub)
+```
+
+### For Zsh:
+
+```
+$ source <(npx --shell-auto-fallback zsh)
+```
+
 ## ACKNOWLEDGEMENTS
 
 Huge thanks to [Kwyn Meagher](https://blog.kwyn.io) for generously donating the package name in the main npm registry. Previously `npx` was used for a Tessel board Neopixels library, which can now be found under [`npx-tessel`](https://npm.im/npx-tessel).

auto-fallback.js

@@ -0,0 +1,46 @@
+'use strict'
+
+const POSIX = `
+command_not_found_handler() {
+  # Do not run within a pipe
+  if test ! -t 1; then
+    echo "command not found: $1"
+    return 127
+  fi
+
+  echo "Trying with npx..."
+  npx $*
+  return $?
+}`
+
+const FISH = `
+function __fish_command_not_found_on_interactive --on-event fish_prompt
+  functions --erase __fish_command_not_found_handler
+  functions --erase __fish_command_not_found_setup
+
+  function __fish_command_not_found_handler --on-event fish_command_not_found
+    echo "Trying with npx..."
+    npx $argv
+  end
+
+  functions --erase __fish_command_not_found_on_interactive
+end`
+
+module.exports = function autoFallback (shell) {
+  const SHELL = process.env.SHELL || ''
+
+  if (shell === 'bash' || SHELL.includes('bash')) {
+    return POSIX.replace('handler()', 'handle()')
+  }
+
+  if (shell === 'zsh' || SHELL.includes('zsh')) {
+    return POSIX
+  }
+
+  if (shell === 'fish' || SHELL.includes('fish')) {
+    return FISH
+  }
+
+  console.error('Only Bash, Zsh, and Fish shells are supported :(')
+  process.exit(1)
+}

index.js

@@ -3,6 +3,7 @@
 
 const BB = require('bluebird')
 
+const autoFallback = require('./auto-fallback.js')
 const cp = require('child_process')
 const getPrefix = require('./get-prefix.js')
 const parseArgs = require('./parse-args.js')
@@ -18,6 +19,12 @@ updateNotifier({pkg}).notify()
 main(parseArgs())
 
 function main (argv) {
+  const shell = argv['shell-auto-fallback']
+  if (shell || shell === '') {
+    console.log(autoFallback(shell))
+    process.exit(0)
+  }
+
   if (!argv.command || !argv.package) {
     console.error('\nERROR: You must supply a command.\n')
     yargs.showHelp()

parse-args.js

@@ -3,7 +3,7 @@
 const npa = require('npm-package-arg')
 const yargs = require('yargs')
 
-const usage = `$0 [--package|-p <package>] [--cache <path>] [--save-dev|-D] [--save-prod|-P] [--save-optional|-O] [--save-bundle|-B] [--save-exact|-E] [--global|-g] [--prefix|-C] [--userconfig <path>] [-c <string>] [--version|-v] [--] <command>[@version] [command-arg]...`
+const usage = `$0 [--package|-p <package>] [--cache <path>] [--save-dev|-D] [--save-prod|-P] [--save-optional|-O] [--save-bundle|-B] [--save-exact|-E] [--global|-g] [--prefix|-C] [--userconfig <path>] [-c <string>] [--shell-auto-fallback [shell]] [--version|-v] [--] <command>[@version] [command-arg]...`
 
 module.exports = parseArgs
 function parseArgs () {
@@ -62,6 +62,12 @@ function parseArgs () {
     type: 'string',
     describe: 'execute string as if inside `npm run-script`'
   })
+  .option('shell-auto-fallback', {
+    choices: ['', 'bash', 'fish', 'zsh'],
+    describe: 'generate shell code to use npx as the "command not found" fallback',
+    requireArg: false,
+    type: 'string'
+  })
   .version()
   .alias('version', 'v')
 

test/auto-fallback.js

@@ -0,0 +1,112 @@
+'use strict'
+
+const exec = require('child_process').exec
+const test = require('tap').test
+
+test('not called with option', (t) =>
+  exec('node .', (err, stdout, stderr) => {
+    t.equal(err.code, 1)
+    t.notOk(stdout)
+    t.match(stderr, /--shell-auto-fallback/)
+    t.end()
+  })
+)
+
+test('detect: SHELL ~= fish', (t) =>
+  exec('node . --shell-auto-fallback', {
+    env: {
+      SHELL: '/usr/bin/fish'
+    }
+  }, (err, stdout, stderr) => {
+    if (err) { throw err }
+    t.match(stdout, /function __fish_command_not_found/)
+    t.notOk(stderr)
+    t.end()
+  })
+)
+
+test('detect: SHELL ~= bash', (t) =>
+  exec('node . --shell-auto-fallback', {
+    env: {
+      SHELL: '/bin/bash'
+    }
+  }, (err, stdout, stderr) => {
+    if (err) { throw err }
+    t.match(stdout, /command_not_found_handle\(/)
+    t.notOk(stderr)
+    t.end()
+  })
+)
+
+test('detect: SHELL ~= zsh', (t) =>
+  exec('node . --shell-auto-fallback', {
+    env: {
+      SHELL: '/usr/local/bin/zsh'
+    }
+  }, (err, stdout, stderr) => {
+    if (err) { throw err }
+    t.match(stdout, /command_not_found_handler\(/)
+    t.notOk(stderr)
+    t.end()
+  })
+)
+
+test('detect: no SHELL', (t) =>
+  exec('node . --shell-auto-fallback', {
+    env: {}
+  }, (err, stdout, stderr) => {
+    t.equal(err.code, 1)
+    t.notOk(stdout)
+    t.match(stderr, /Only .+ shells are supported :\(/)
+    t.end()
+  })
+)
+
+test('detect: SHELL ~= unsupported', (t) =>
+  exec('node . --shell-auto-fallback', {
+    env: {
+      SHELL: '/sbin/nope'
+    }
+  }, (err, stdout, stderr) => {
+    t.equal(err.code, 1)
+    t.notOk(stdout)
+    t.match(stderr, /Only .+ shells are supported :\(/)
+    t.end()
+  })
+)
+
+test('given: fish', (t) =>
+  exec('node . --shell-auto-fallback fish', (err, stdout, stderr) => {
+    if (err) { throw err }
+    t.match(stdout, /function __fish_command_not_found/)
+    t.notOk(stderr)
+    t.end()
+  })
+)
+
+test('given: bash', (t) =>
+  exec('node . --shell-auto-fallback bash', (err, stdout, stderr) => {
+    if (err) { throw err }
+    t.match(stdout, /command_not_found_handle\(/)
+    t.notOk(stderr)
+    t.end()
+  })
+)
+
+test('given: zsh', (t) =>
+  exec('node . --shell-auto-fallback zsh', (err, stdout, stderr) => {
+    if (err) { throw err }
+    t.match(stdout, /command_not_found_handler\(/)
+    t.notOk(stderr)
+    t.end()
+  })
+)
+
+test('given: unsupported', (t) =>
+  exec('node . --shell-auto-fallback nope', (err, stdout, stderr) => {
+    t.equal(err.code, 1)
+    t.notOk(stdout)
+    t.match(stderr, /Invalid values:\s+Argument: shell-auto-fallback/)
+    t.end()
+  })
+)