Merge pull request #396 from oclif/sm/distance-algo

refactor: algo and test for it

src/index.ts

@@ -2,6 +2,9 @@ import {color} from '@oclif/color'
 import {Hook, toConfiguredId, ux} from '@oclif/core'
 import * as Levenshtein from 'fast-levenshtein'
 
+export const closest = (target: string, possibilities: string[]): string =>
+  possibilities.map(id => ({id, distance: Levenshtein.get(target, id)})).sort((a, b) => a.distance - b.distance)[0]?.id ?? ''
+
 const hook: Hook.CommandNotFound = async function (opts) {
   const hiddenCommandIds = new Set(opts.config.commands.filter(c => c.hidden).map(c => c.id))
   const commandIDs = [
@@ -10,15 +13,6 @@ const hook: Hook.CommandNotFound = async function (opts) {
   ].filter(c => !hiddenCommandIds.has(c))
 
   if (commandIDs.length === 0) return
-  function closest(cmd: string): string {
-    // we'll use this array to keep track of which key is the closest to the users entered value.
-    // keys closer to the index 0 will be a closer guess than keys indexed further from 0
-    // an entry at 0 would be a direct match, an entry at 1 would be a single character off, etc.
-    const index: string[] = []
-    // eslint-disable-next-line no-return-assign
-    commandIDs.map(id => (index[Levenshtein.get(cmd, id)] = id))
-    return index.find(item => item !== undefined) ?? ''
-  }
 
   let binHelp = `${opts.config.bin} help`
   const idSplit = opts.id.split(':')
@@ -27,7 +21,8 @@ const hook: Hook.CommandNotFound = async function (opts) {
     binHelp = `${binHelp} ${idSplit[0]}`
   }
 
-  const suggestion = closest(opts.id)
+  const suggestion = closest(opts.id, commandIDs)
+
   const readableSuggestion = toConfiguredId(suggestion, this.config)
   const originalCmd = toConfiguredId(opts.id, this.config)
   this.warn(`${color.yellow(originalCmd)} is not a ${opts.config.bin} command.`)

test/closest.test.ts

@@ -0,0 +1,37 @@
+import {closest} from '../src'
+import {expect} from 'chai'
+
+describe('closest', () => {
+  const possibilities = ['abc', 'def', 'ghi', 'jkl', 'jlk']
+  it('exact match', () => {
+    expect(closest('abc', possibilities)).to.equal('abc')
+  })
+
+  it('case mistake', () => {
+    expect(closest('aBc', possibilities)).to.equal('abc')
+  })
+
+  it('case match one letter', () => {
+    expect(closest('aZZ', possibilities)).to.equal('abc')
+  })
+
+  it('one letter different mistake', () => {
+    expect(closest('ggi', possibilities)).to.equal('ghi')
+  })
+
+  it('two letter different mistake', () => {
+    expect(closest('gki', possibilities)).to.equal('ghi')
+  })
+
+  it('extra letter', () => {
+    expect(closest('gkui', possibilities)).to.equal('ghi')
+  })
+
+  it('two letter different mistake with close neighbor', () => {
+    expect(closest('jpp', possibilities)).to.equal('jkl')
+  })
+
+  it('no possibilities gives empty string', () => {
+    expect(closest('jpp', [])).to.equal('')
+  })
+})