Introduce related spans into tsserver protocol (#24548)

* Introduce related spans into tsserver protocol

* Incorporate pretty output, implement esModuleInterop related span

src/server/protocol.ts

@@ -466,6 +466,7 @@ namespace ts.server.protocol {
         code: number;
         /** May store more in future. For now, this will simply be `true` to indicate when a diagnostic is an unused-identifier diagnostic. */
         reportsUnnecessary?: {};
+        relatedInformation?: DiagnosticRelatedInformation[];
     }
 
     /**
@@ -2215,6 +2216,11 @@ namespace ts.server.protocol {
 
         reportsUnnecessary?: {};
 
+        /**
+         * Any related spans the diagnostic may have, such as other locations relevant to an error, such as declarartion sites
+         */
+        relatedInformation?: DiagnosticRelatedInformation[];
+
         /**
          * The error code of the diagnostic message.
          */
@@ -2233,6 +2239,23 @@ namespace ts.server.protocol {
         fileName: string;
     }
 
+    /**
+     * Represents additional spans returned with a diagnostic which are relevant to it
+     * Like DiagnosticWithLinePosition, this is provided in two forms:
+     *   - start and length of the span
+     *   - startLocation and endLocation a pair of Location objects storing the start/end line offset of the span
+     */
+    export interface DiagnosticRelatedInformation {
+        /**
+         * Text of related or additional information.
+         */
+        message: string;
+        /**
+         * Associated location
+         */
+        span?: FileSpan;
+    }
+
     export interface DiagnosticEventBody {
         /**
          * The file for which diagnostic information is reported.