derivative() does not support the full range of symbol characters

DESCRIBE THE BUG

The documentation lists the characters one can use in variable / symbol names, including a-z, A-Z, $, _, etc.

However, supplying a symbol in a string to derive against with anything but basic alphanumerics to derivative() fails.

Apologies in advance if this has already been reported; I looked through the Issues but didn't see an obvious similar report.

TO REPRODUCE

I'll use a variable with a '$' character in here for reference, but the same thing happened when using '_' in a variable name.

Problem is present in math.js 13.0.2 and 13.0.3.

To start, evaluate() works fine with these characters:

import * as math from "mathjs"
console.log(math.evaluate("1 + p$x", { p$x: 1 }))

"2"

But calling derivative() fails with the same symbol:

import * as math from "mathjs"
var d = math.derivative("1 + p$x", "p$x")
console.log(d.toString())

"TypeError: Unexpected type of argument in function derivative (expected: SymbolNode or identifier, actual: string, index: 1)"

Calling it with a boring symbol works, though:

import * as math from "mathjs"
var d = math.derivative("1 + px", "px")
console.log(d.toString())

"1"

We can get around this problem by parsing the symbol first:

import * as math from "mathjs"
var x = math.parse("p$x")
var d = math.derivative("1 + p$x", x)
console.log(d.toString())

"1"

For completeness, here is the failure using a variable with an underscore:

import * as math from "mathjs"
var d = math.derivative("1 + p_x", "p_x")
console.log(d.toString())

"TypeError: Unexpected type of argument in function derivative (expected: SymbolNode or identifier, actual: string, index: 1)"

josdejong / mathjs

derivative() does not support the full range of symbol characters #3253

DESCRIBE THE BUG

TO REPRODUCE