fix: obey hover markup kind capability

metals-bench/src/main/scala/bench/ClasspathOnlySymbolSearch.scala

@@ -6,6 +6,7 @@ import java.{util => ju}
 
 import scala.meta.internal.metals.ClasspathSearch
 import scala.meta.internal.metals.WorkspaceSymbolQuery
+import scala.meta.pc.ContentType
 import scala.meta.pc.ParentSymbols
 import scala.meta.pc.SymbolDocumentation
 import scala.meta.pc.SymbolSearch
@@ -26,6 +27,12 @@ class ClasspathOnlySymbolSearch(classpath: ClasspathSearch)
   ): Optional[SymbolDocumentation] =
     Optional.empty()
 
+  override def documentation(
+      symbol: String,
+      parents: ParentSymbols,
+      docstringContentType: ContentType,
+  ): Optional[SymbolDocumentation] = Optional.empty()
+
   def definition(symbol: String, source: URI): ju.List[Location] =
     ju.Collections.emptyList()
 

metals/src/main/scala/scala/meta/internal/metals/ClientConfiguration.scala

@@ -3,6 +3,7 @@ package scala.meta.internal.metals
 import scala.meta.internal.metals.Configs.GlobSyntaxConfig
 import scala.meta.internal.metals.config.DoctorFormat
 import scala.meta.internal.metals.config.StatusBarState
+import scala.meta.pc.ContentType
 
 import org.eclipse.lsp4j.ClientCapabilities
 import org.eclipse.lsp4j.InitializeParams
@@ -161,6 +162,18 @@ final class ClientConfiguration(
     } yield true
   }.getOrElse(false)
 
+  def hoverContentType(): ContentType =
+    (for {
+      capabilities <- clientCapabilities
+      textDocumentCapabilities <- Option(capabilities.getTextDocument())
+      hoverCapabilities <- Option(textDocumentCapabilities.getHover())
+      contentTypes <- Option(hoverCapabilities.getContentFormat())
+    } yield {
+      if (contentTypes.contains(ContentType.MARKDOWN.toString()))
+        ContentType.MARKDOWN
+      else ContentType.PLAINTEXT
+    }).getOrElse(ContentType.MARKDOWN)
+
   def isTreeViewProvider(): Boolean =
     extract(
       initializationOptions.treeViewProvider,

metals/src/main/scala/scala/meta/internal/metals/CompilerConfiguration.scala

@@ -239,6 +239,7 @@ class CompilerConfiguration(
               initializeParams.supportsCompletionSnippets,
             _isStripMarginOnTypeFormattingEnabled =
               () => userConfig().enableStripMarginOnTypeFormatting,
+            hoverContentType = config.hoverContentType(),
           )
       }
 

metals/src/main/scala/scala/meta/internal/metals/Compilers.scala

@@ -726,8 +726,9 @@ class Compilers(
       token: CancelToken,
   ): Future[Option[HoverSignature]] = {
     withPCAndAdjustLsp(params) { (pc, pos, adjust) =>
-      pc.hover(CompilerRangeParamsUtils.offsetOrRange(pos, token))
-        .asScala
+      pc.hover(
+        CompilerRangeParamsUtils.offsetOrRange(pos, token)
+      ).asScala
         .map(_.asScala.map { hover => adjust.adjustHoverResp(hover) })
     }
   }.getOrElse(Future.successful(None))

metals/src/main/scala/scala/meta/internal/metals/InlayHintResolveProvider.scala

@@ -69,7 +69,11 @@ final class InlayHintResolveProvider(
     )
     compilers.hover(hoverParams, token).map { hover =>
       hover
-        .foreach(h => labelPart.setTooltip(h.toLsp().getContents().getRight()))
+        .foreach(h =>
+          labelPart.setTooltip(
+            h.toLsp().getContents().getRight()
+          )
+        )
       labelPart
     }
   }

metals/src/main/scala/scala/meta/internal/metals/MetalsSymbolSearch.scala

@@ -9,6 +9,7 @@ import scala.collection.concurrent.TrieMap
 import scala.meta.internal.metals.MetalsEnrichments._
 import scala.meta.internal.mtags.Mtags
 import scala.meta.io.AbsolutePath
+import scala.meta.pc.ContentType
 import scala.meta.pc.ParentSymbols
 import scala.meta.pc.SymbolDocumentation
 import scala.meta.pc.SymbolSearch
@@ -40,7 +41,14 @@ class MetalsSymbolSearch(
       symbol: String,
       parents: ParentSymbols,
   ): Optional[SymbolDocumentation] =
-    docs.documentation(symbol, parents)
+    documentation(symbol, parents, ContentType.MARKDOWN)
+
+  override def documentation(
+      symbol: String,
+      parents: ParentSymbols,
+      contentType: ContentType,
+  ): Optional[SymbolDocumentation] =
+    docs.documentation(symbol, parents, contentType)
 
   def definition(symbol: String, source: URI): ju.List[Location] = {
     val sourcePath = Option(source).map(AbsolutePath.fromAbsoluteUri)

metals/src/main/scala/scala/meta/internal/metals/StandaloneSymbolSearch.scala

@@ -11,6 +11,7 @@ import scala.meta.internal.mtags.Mtags
 import scala.meta.internal.mtags.OnDemandSymbolIndex
 import scala.meta.internal.parsing.Trees
 import scala.meta.io.AbsolutePath
+import scala.meta.pc.ContentType
 import scala.meta.pc.ParentSymbols
 import scala.meta.pc.SymbolDocumentation
 import scala.meta.pc.SymbolSearch
@@ -64,12 +65,21 @@ class StandaloneSymbolSearch(
   def documentation(
       symbol: String,
       parents: ParentSymbols,
+  ): ju.Optional[SymbolDocumentation] =
+    documentation(symbol, parents, docstringContentType = ContentType.MARKDOWN)
+
+  override def documentation(
+      symbol: String,
+      parents: ParentSymbols,
+      docstringContentType: ContentType,
   ): ju.Optional[SymbolDocumentation] =
     docs
-      .documentation(symbol, parents)
+      .documentation(symbol, parents, docstringContentType)
       .asScala
       .orElse(
-        workspaceFallback.flatMap(_.documentation(symbol, parents).asScala)
+        workspaceFallback.flatMap(
+          _.documentation(symbol, parents, docstringContentType).asScala
+        )
       )
       .asJava
 

mtags-interfaces/src/main/java/scala/meta/pc/ContentType.java

@@ -0,0 +1,16 @@
+package scala.meta.pc;
+
+public enum ContentType {
+  MARKDOWN("markdown"),
+  PLAINTEXT("plaintext");
+
+  private final String name;
+  ContentType(String name) {
+      this.name = name;
+  }
+
+  @Override
+  public String toString() {
+      return name;
+  }
+}

mtags-interfaces/src/main/java/scala/meta/pc/HoverSignature.java

@@ -10,4 +10,7 @@ public interface HoverSignature {
   Optional<String> signature();
   Optional<Range> getRange();
   HoverSignature withRange(Range range);
+  default ContentType contentType() {
+    return ContentType.MARKDOWN;
+  }
 }

mtags-interfaces/src/main/java/scala/meta/pc/PresentationCompiler.java

@@ -166,14 +166,16 @@ public abstract CompletableFuture<List<TextEdit>> convertToNamedArguments(Offset
 	public abstract CompletableFuture<List<Diagnostic>> didChange(VirtualFileParams params);
 
 	/**
-	 * Returns decorations for missing type adnotations, inferred type parameters, implicit parameters and conversions.
+	 * Returns decorations for missing type adnotations, inferred type parameters,
+	 * implicit parameters and conversions.
 	 */
 	public CompletableFuture<List<InlayHint>> inlayHints(InlayHintsParams params) {
 		return CompletableFuture.completedFuture(Collections.emptyList());
 	}
 
 	/**
-	 * Returns decorations for missing type adnotations, inferred type parameters, implicit parameters and conversions.
+	 * Returns decorations for missing type adnotations, inferred type parameters,
+	 * implicit parameters and conversions.
 	 */
 	public CompletableFuture<List<SyntheticDecoration>> syntheticDecorations(SyntheticDecorationsParams params) {
 		return CompletableFuture.completedFuture(Collections.emptyList());