fix: #3141 help(config) altering the actual config when evaluating the examples

Author: josdejong

HISTORY.md

@@ -14,6 +14,8 @@
   for the option `wordSize` in the functions `hex`, `bin`, and `oct`. 
 - Fix: #3125 type definitions of function `hypot` (#3144). 
   Thanks @silentmissile.
+- Fix: #3141 `help(config)` altering the actual `config` when evaluating the 
+  examples.
 - Docs: #3145 fix documentation about REPL, it does require a build step 
   nowadays.
 

src/expression/Help.js

@@ -4,9 +4,9 @@ import { format } from '../utils/string.js'
 import { factory } from '../utils/factory.js'
 
 const name = 'Help'
-const dependencies = ['parse']
+const dependencies = ['evaluate']
 
-export const createHelpClass = /* #__PURE__ */ factory(name, dependencies, ({ parse }) => {
+export const createHelpClass = /* #__PURE__ */ factory(name, dependencies, ({ evaluate }) => {
   /**
    * Documentation object
    * @param {Object} doc  Object containing properties:
@@ -58,15 +58,26 @@ export const createHelpClass = /* #__PURE__ */ factory(name, dependencies, ({ pa
     if (doc.examples) {
       desc += 'Examples:\n'
 
-      const scope = {}
+      // after evaluating the examples, we restore config in case the examples
+      // did change the config.
+      let configChanged = false
+      const originalConfig = evaluate('config()')
+
+      const scope = {
+        config: (newConfig) => {
+          configChanged = true
+          return evaluate('config(newConfig)', { newConfig })
+        }
+      }
+
       for (let i = 0; i < doc.examples.length; i++) {
         const expr = doc.examples[i]
         desc += '    ' + expr + '\n'
 
         let res
         try {
           // note: res can be undefined when `expr` is an empty string
-          res = parse(expr).compile().evaluate(scope)
+          res = evaluate(expr, scope)
         } catch (e) {
           res = e
         }
@@ -75,6 +86,10 @@ export const createHelpClass = /* #__PURE__ */ factory(name, dependencies, ({ pa
         }
       }
       desc += '\n'
+
+      if (configChanged) {
+        evaluate('config(originalConfig)', { originalConfig })
+      }
     }
     if (doc.mayThrow && doc.mayThrow.length) {
       desc += 'Throws: ' + doc.mayThrow.join(', ') + '\n\n'

test/generated-code-tests/entry/mainAny.test.js

@@ -119,7 +119,7 @@ describe('mainAny', function () {
     assert.deepStrictEqual(scope, { b: 2 })
   })
 
-  it('should evaluate assignement and access', function () {
+  it('should evaluate assignment and access', function () {
     const math = create(all)
     const evaluate = math.evaluate
 

test/unit-tests/expression/function/help.test.js

@@ -26,6 +26,13 @@ describe('help', function () {
     assert.strictEqual(help.doc.name, 'sin')
   })
 
+  it('should not alter the mathjs instance when stringifying help', function () {
+    const config = math.config()
+    const str = math.help(math.config).toString()
+    assert(str.includes('number: "Fraction"'))
+    assert.deepStrictEqual(math.config(), config)
+  })
+
   it('should find help from a function', function () {
     const help = math.help(math.sin)
     assert(help instanceof math.Help)