Task fails with ambiguous error on JSON file that has comments

[norvegec]

Before opening an issue please read this.

Are you reporting a bug or a feature request ?

• [ ] Bug
• [x] Feature request

Description

When JSON content of input file has comments the task fails with ambiguous message:

##[error]Couldn't apply patch to file: C:\myTargetDir\_configs\appsettings.dev.json
##[error]No files were patched.

Expected behavior

• Good: output an error that would clearly point to a problem: "malformed JSON content" or "unsupported JSON content at line XXX", etc.
• Better: ignore comments in JSON

Reproduction

Add this task (ver. 3/4) to a pipeline that works with filesystem (Azure Pipeline Windows 2019 agent pool) with options:

• Syntax type: Slick Syntax,
• Target files: appsettings.$(env).json
• Patch content:
• Output patched file in logs: checked
• Fail if no files are patched: checked

and taking into account that file actually exist the task logs ambiguous error:

##[error]Couldn't apply patch to file: C:\myTargetDir\_configs\appsettings.dev.json
##[error]No files were patched."

# System information

**VSTS or TFS:**
* [x] VSTS
* [ ] TFS

**Agent:**
* [x] Hosted
* [ ] Custom

**OS:**
* [x] Windows
* [ ] Mac
* [ ] Linux

[norvegec]

Since then, I've discovered that JSON5 format is supported and works fine when corresponding option is checked. Maybe an error could give user a hint to use this flag?