canonical/multipass

Handle yaml-cpp exceptions from a cloud-init config better

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#646 opened on Feb 28, 2019

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 (4 comments) (0 reactions) (1 assignee)C++ (6,956 stars) (634 forks)batch import
enhancementgood first issue

Description

Currently, we just bubble up any yaml-cpp exceptions back to the client, but the error message is out of context of what is really wrong. For example, if a user creates a cloud-init config with incorrect yaml, an error could look like: launch failed: operator[] call on a scalar As can be seen, it's not clear where the error is.

We should catch the yaml-cpp exceptions and make it a more meaningful message to pass to the client and user.

Contributor guide

Tech stack
cpp
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C++ basicsyaml cpp familiarityexception handling
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
The issue is to improve error messages from yaml cpp exceptions in cloud init config parsing. The repository is multipass (C++). Look for files related to cloud init config parsing, likely in src/cloud init or similar. Check for existing exception handling patterns. The issue has an assignee, so coordinate with them before starting work. Consider adding context about which config file caused the error. Review existing tests for yaml parsing and update them accordingly.