Update error output to be more readable

[FrenchBen]

• Don't space out the error but append the next one
• During a test, type the expected result instead of parsing it

Current error output looks like:

Error applying plan:

3 error(s) occurred:

* azurerm_network_interface.machine1: 1 error(s) occurred:

* azurerm_network_interface.machine1: <some error string goes here>
* azurerm_network_interface.machine1: <some error string goes here>
* azurerm_network_interface.machine2: 1 error(s) occurred:

* azurerm_network_interface.machine: <some error string goes here>

This changes it to be:

Error applying plan:

3 error(s) occurred:
* azurerm_network_interface.machine1: 2 error(s) occurred:
    * azurerm_network_interface.machine1: <some error string goes here>
    * azurerm_network_interface.machine1: <some error string goes here>

* azurerm_network_interface.machine2: 1 error(s) occurred:
    * azurerm_network_interface.machine2: <some error string goes here>

Which imho makes things more readable.

[mitchellh]

This looks pretty promising. @hashicorp/terraform-core what do you think?

[jbardin]

Hi @mitchellh,

I think this looks good, though I don't think it's not going to be directly useful in Terraform moving forward.

We're moving the handling all warnings and errors to a single Diagnostics type, which does its own formatting (and besides combining the handling warnings and errors, it also allows other features like correlating any configuration related errors back to the original source location). When remaining uses of multierror are appended to Diagnostics they are unpacked into separate errors to be formatted later for the user.

[apparentlymart]

Looks like a nice improvement to me!

Note though that Terraform will be using go-multierror a lot less from 0.12 onwards because we're switching to a HCL2-inspired "diagnostics" model for most things. This allows us to include source code snippets in the output:

This change will be nice for other go-multierror callers, though!

[apparentlymart]

Oh heh... I guess I should reload before I post a comment I've had sitting in my browser for 30 minutes. :wink:

[FrenchBen]

What's the overall consensus? Should I close this PR and wait for the HCL-2 release?

[apparentlymart]

I think this is good to merge, regardless of how Terraform is changing. I think we were just a little unclear with each other about who was going to own merging this. 🙄

I'm not at a computer right now but I will merge this tomorrow if Mitchell or James doesn't beat me to it, but they are in earlier timezones than me so they might get there first!