chore: enable mutating flat-options

This will allow for changing configs that are read by commands through
flatOptions.

Based of npm#2795, land that first.

Relates to: npm#2765
Relates to: npm/rfcs#117

lib/npm.js

@@ -42,7 +42,6 @@ const { shellouts } = require('./utils/cmd-list.js')
 let warnedNonDashArg = false
 const _runCmd = Symbol('_runCmd')
 const _load = Symbol('_load')
-const _flatOptions = Symbol('_flatOptions')
 const _tmpFolder = Symbol('_tmpFolder')
 const _title = Symbol('_title')
 const npm = module.exports = new class extends EventEmitter {
@@ -140,9 +139,6 @@ const npm = module.exports = new class extends EventEmitter {
       if (!er && this.config.get('force'))
         this.log.warn('using --force', 'Recommended protections disabled.')
 
-      if (!er && !this[_flatOptions])
-        this[_flatOptions] = require('./utils/flat-options.js')(this)
-
       process.emit('timeEnd', 'npm:load')
       this.emit('load', er)
     })
@@ -203,7 +199,7 @@ const npm = module.exports = new class extends EventEmitter {
   }
 
   get flatOptions () {
-    return this[_flatOptions]
+    return require('./utils/flat-options.js')(this)
   }
 
   get lockfileVersion () {

lib/utils/flat-options.js

@@ -190,7 +190,7 @@ const flatten = obj => ({
   noProxy: obj.noproxy,
 })
 
-const flatOptions = npm => npm.flatOptions || Object.freeze({
+const flatOptions = npm => Object.freeze({
   // flatten the config object
   ...flatten(npm.config.list[0]),
 

test/lib/utils/flat-options.js

@@ -150,9 +150,6 @@ t.test('basic', t => {
   // test the object is frozen
   generatedFlat.newField = 'asdf'
   t.equal(generatedFlat.newField, undefined, 'object is frozen')
-  const preExistingOpts = { flat: 'options' }
-  npm.flatOptions = preExistingOpts
-  t.equal(flatOptions(npm), preExistingOpts, 'use pre-existing npm.flatOptions')
   t.end()
 })