Throws uncaught error on malformed variable substitutions

[bogini]

Summary

The parse() function in shell-quote throws an uncaught error when encountering malformed shell variable substitutions. This happens with patterns like ${result (missing closing brace) or other invalid variable substitution syntax.

Environment

• shell-quote version: 1.8.1
• Node.js version: v22.17.0
• OS: Linux/macOS/Windows

Current Behavior

When parsing commands with malformed variable substitutions, shell-quote throws an error:

Error: Bad substitution: result
    at parseEnvVar (/node_modules/shell-quote/parse.js:128:12)
    at <anonymous> (/node_modules/shell-quote/parse.js:189:12)
    at Array.map (<anonymous>)
    at parseInternal (/node_modules/shell-quote/parse.js:89:17)
    at Object.parse (/node_modules/shell-quote/parse.js:207:15)

Expected Behavior

The parser should either:

1. Return the malformed syntax as-is (treating it as a literal string)
2. Return an error object that can be handled gracefully
3. Provide an option to handle parsing errors without throwing

Steps to Reproduce

const { parse } = require('shell-quote');

// These all throw "Bad substitution" errors:
parse('echo ${result');        // Error: Bad substitution: result
parse('${VAR');                // Error: Bad substitution: VAR
parse('test ${a ${b');         // Error: Bad substitution: a ${b
parse('command ${');           // Error: Bad substitution: 
parse('ls ${PATH }');          // Error: Bad substitution: PATH }

Additional Context

This is particularly problematic in interactive applications where users might type commands incrementally or make syntax errors. The current behavior makes it impossible to provide helpful error messages or syntax highlighting for malformed commands.

[ljharb]

Why is this the expected behavior? If you provide bad data, an exception is pretty objectively the correct behavior - you can handle that gracefully yourself with try/catch, just like you would an error object.