Improve generator parse error handling

[SuperQ]

Improve the handling of parse errors from net-snmp.

• Fix the line split when there are no errors.
• Default to failing on parse errors.
• Add extra help messages to help when there are errors.
• Improve parse_errors output.

[SuperQ]

So in previous combinations of the generator and net-snmp we would get missing MIB file information in the STDERR output of net-snmp. This would be easy to parse and print back to the user. But in the version I'm testing here the information is missing and I'm not sure why.

[SuperQ]

CC @bastischubert

[bastischubert]

But in the version I'm testing here the information is missing and I'm not sure why.

Can you share which versions you're using ;)

[SuperQ]

It looks like the difference is between net-snmp 5.7 and 5.9. Previously we would show errors like this:

Cannot find module (SNMPv2-TC): At line 8 in mibs/HOST-RESOURCES-MIB

But that is not included anymore. If I use snmpwalk -m, it produces the error. So there is something about the way we call the C code that makes the errors not show up in newer net-snmp versions.

[SuperQ]

For now, I think we should go ahead with this change. It's still useful as-is. We can continue to work on the generator error parsing later.

[bastischubert]

adding --snmp.mibopts=e produces the desired behaviour with net-snmp >= 5.9.x

[bastischubert]

We should add that param to the Makefile

diff --git a/generator/Makefile b/generator/Makefile
index 579610d..bb7530a 100644
--- a/generator/Makefile
+++ b/generator/Makefile
@@ -70,7 +70,7 @@ generate: generator mibs
        MIBDIRS=$(MIB_PATH) ./generator --fail-on-parse-errors generate

 parse_errors: generator mibs
-       MIBDIRS=$(MIB_PATH) ./generator --fail-on-parse-errors parse_errors
+       MIBDIRS=$(MIB_PATH) ./generator --fail-on-parse-errors parse_errors --snmp.mibopts=e

 .PHONY: docker
 docker:```

[SuperQ]

Easier, I added e to the default options.

[SuperQ]

The error output is now much easier to read:

$ MIBDIRS=mibs ./generator generate
ts=2024-05-05T19:09:48.112Z caller=net_snmp.go:175 level=info msg="Loading MIBs" from=mibs
ts=2024-05-05T19:09:48.258Z caller=main.go:177 level=warn msg="NetSNMP reported parse error(s)" errors=2453
ts=2024-05-05T19:09:48.258Z caller=main.go:183 level=error msg="Missing MIB" mib=AIRESPACE-REF-MIB from="At line 66 in mibs/AIRESPACE-WIRELESS-MIB"
ts=2024-05-05T19:09:48.337Z caller=main.go:135 level=error msg="Failing on reported parse error(s)" help="Use 'generator parse_errors' command to see errors, --no-fail-on-parse-errors to ignore"

[RichiH]

LGTM Sent by mobile; please excuse my brevity.

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