Promise interface

Close #65

README.md

@@ -17,6 +17,9 @@ which('node', function (er, resolvedPath) {
   // if it is found, then the absolute path to the exec is returned
 })
 
+// or promise
+which('node').then(resolvedPath => { ... }).catch(er => { ... not found ... })
+
 // sync usage
 // throws if not found
 var resolved = which.sync('node')

test/basic.js

@@ -21,11 +21,10 @@ t.test('setup', function (t) {
 })
 
 t.test('does not find missed', function(t) {
-  t.plan(4)
+  t.plan(3)
 
-  which(fixture + '/foobar.sh', function (er) {
-    t.isa(er, Error)
-    t.equal(er.code, 'ENOENT')
+  t.rejects(which(fixture + '/foobar.sh'), {
+    code: 'ENOENT',
   })
 
   t.throws(function () {
@@ -181,13 +180,10 @@ t.test('find all', t => {
     colon: ':',
     all: true,
   }
-  which('x.cmd', opt, (er, all) => {
-    if (er)
-      throw er
+  const allsync = which.sync('x.cmd', opt)
+  t.same(allsync, [`${fixture}/all/a/x.cmd`, `${fixture}/all/b/x.cmd`])
+  return which('x.cmd', opt).then(all => {
     t.same(all, [`${fixture}/all/a/x.cmd`, `${fixture}/all/b/x.cmd`])
-    const allsync = which.sync('x.cmd', opt)
-    t.same(allsync, [`${fixture}/all/a/x.cmd`, `${fixture}/all/b/x.cmd`])
-    t.end()
   })
 })
 

which.js

@@ -45,17 +45,16 @@ const which = (cmd, opt, cb) => {
     cb = opt
     opt = {}
   }
+  if (!opt)
+    opt = {}
 
   const { pathEnv, pathExt, pathExtExe } = getPathInfo(cmd, opt)
   const found = []
 
-  const F = i => {
-    if (i === pathEnv.length) {
-      if (opt.all && found.length)
-        return cb(null, found)
-      else
-        return cb(getNotFoundError(cmd))
-    }
+  const step = i => new Promise((resolve, reject) => {
+    if (i === pathEnv.length)
+      return opt.all && found.length ? resolve(found)
+        : reject(getNotFoundError(cmd))
 
     const ppRaw = pathEnv[i]
     const pathPart = /^".*"$/.test(ppRaw) ? ppRaw.slice(1, -1) : ppRaw
@@ -64,23 +63,25 @@ const which = (cmd, opt, cb) => {
     const p = !pathPart && /^\.[\\\/]/.test(cmd) ? cmd.slice(0, 2) + pCmd
       : pCmd
 
-    const E = (ii) => {
-      if (ii === pathExt.length)
-        return F(i + 1)
-      const ext = pathExt[ii]
-      isexe(p + ext, { pathExt: pathExtExe }, (er, is) => {
-        if (!er && is) {
-          if (opt.all)
-            found.push(p + ext)
-          else
-            return cb(null, p + ext)
-        }
-        return E(ii + 1, pathExt.length)
-      })
-    }
-    return E(0)
-  }
-  return F(0)
+    resolve(subStep(p, i, 0))
+  })
+
+  const subStep = (p, i, ii) => new Promise((resolve, reject) => {
+    if (ii === pathExt.length)
+      return resolve(step(i + 1))
+    const ext = pathExt[ii]
+    isexe(p + ext, { pathExt: pathExtExe }, (er, is) => {
+      if (!er && is) {
+        if (opt.all)
+          found.push(p + ext)
+        else
+          return resolve(p + ext)
+      }
+      return resolve(subStep(p, i, ii + 1))
+    })
+  })
+
+  return cb ? step(0).then(res => cb(null, res), cb) : step(0)
 }
 
 const whichSync = (cmd, opt) => {