[clang] [clang-tools-extra] [llvm] [clang] Introduce diagnostics suppression mappings (PR #112517)

[Aaron Ballman via cfe-commits]

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@@ -1315,6 +1319,34 @@ with its corresponding `Wno-` option.
 Note that when combined with :option:`-w` (which disables all warnings),
 disabling all warnings wins.
 
+.. _warning_suppression_mappings:
+
+Controlling Diagnostics via Suppression Mappings
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Warning suppression mappings enable users to suppress Clang's diagnostics in a
+per-file granular manner. Enabling enforcement of diagnostics in specific parts
+of the project, even if there are violations in some headers.
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AaronBallman wrote:

That's true, but I think we want to guide users towards fixing diagnostics rather than suppressing them. Users will use any suppression mechanisms we provide regardless of how we document it, so I don't think it's harmful to imply this is more about cases where you can't modify the code. But I also don't feel strongly. WDYT?

https://github.com/llvm/llvm-project/pull/112517