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https://issues.apache.org/jira/browse/MESOS-3754?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Michael Park updated MESOS-3754:
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Summary: Update the style guide with a rule regarding the use of default
case in switch statements (was: Update the style guide with a rule around the
use of default case in switch statements)
> Update the style guide with a rule regarding the use of default case in
> switch statements
> -----------------------------------------------------------------------------------------
>
> Key: MESOS-3754
> URL: https://issues.apache.org/jira/browse/MESOS-3754
> Project: Mesos
> Issue Type: Bug
> Components: documentation
> Reporter: Michael Park
>
> This is the continuation of the initial discussions started on MESOS-2664.
> The motivation is to rely on the compiler for compile-time errors for cases
> missing in the {{switch}} statement, rather than aborting in the {{default}}
> case at runtime.
> The pattern we want to avoid is a {{switch}} statement that fully enumerates
> the cases of an {{enum}} *and* having a {{default}} case that aborts at
> runtime. The preferred approach is to omit the {{default}} case.
> This pattern can be seen across the codebase, one example is:
> {code}
> switch (volume.mode()) {
> case Volume::RW: volumeConfig += ":rw"; break;
> case Volume::RO: volumeConfig += ":ro"; break;
> default:
> LOG(FATAL) << "Unknown Volume mode: " << volume.mode();
> break;
> }
> {code}
> The proposal is not to disallow uses of {{default}} cases, but to only use
> them when it actually carries some meaningful fallback behavior.
> This use of {{default}} leads to the following advantages:
> 1. If we miss any of the cases, you get notified via a compiler-error.
> 2. If a new value is added to an {{enum}}, the compiler reports all of the
> places that needs to be updated to handle the new value.
> Ideally, the compiler would also prevent us from covering all enumerations
> *and* providing a {{default}}. Since this is not an available option, we aim
> to capture this as a style guideline.
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