[clang-tools-extra] [clangd] Implement LSP 3.17 positionEncoding (PR #142903)

[kadir çetinkaya via cfe-commits]

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@@ -497,6 +497,12 @@ bool fromJSON(const llvm::json::Value &Params, ClientCapabilities &R,
       if (auto Cancel = StaleRequestSupport->getBoolean("cancel"))
         R.CancelsStaleRequests = *Cancel;
     }
+    if (auto *OffsetEncoding = General->get("positionEncodings")) {
+      R.offsetEncoding.emplace();
+      if (!fromJSON(*OffsetEncoding, *R.offsetEncoding,
+                    P.field("general").field("positionEncodings")))
+        return false;
+    }
   }
   if (auto *OffsetEncoding = O->get("offsetEncoding")) {
     R.offsetEncoding.emplace();
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kadircet wrote:

thanks, but I think just a simple log message here is sufficient, and we deliberately don't need more (neither the message shown, nor the new field).

- I don't think we should have 2 representations in the internal C++ representation, to make sure canonicalization happens at a single place and rest of the logic that relies on this option doesn't have visibility into both versions. Though we can call this field `PositionEncodings` now to align with the standard.
- Showing a message to user is too disruptive. It'll pop up on every startup. Moreover the user can't do anything to suppress that, extension author needs to take action.

https://github.com/llvm/llvm-project/pull/142903