improvement: Make including detail in completion label configurable

Some LSP clients (such as Emacs using Eglot and Corfu) use the label field to insert a completion if
completionItem/resolve has not returned by the time the completion is selected. Including the contents of the detail
property in the label causes it to be included in the file itself in these clients. To remedy this, we define a
isDetailIncludedInLabel option under compilerOptions to make this behaviour toggleable. We also disable this behaviour
by default in Emacs, since this is where the undesirable behaviour was located.

Fixes #6849.

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

@@ -200,6 +200,9 @@ object InitializationOptions {
       isSignatureHelpDocumentationEnabled = compilerObj.flatMap(
         _.getBooleanOption("isSignatureHelpDocumentationEnabled")
       ),
+      isDetailIncludedInLabel = compilerObj.flatMap(
+        _.getBooleanOption("isDetailIncludedInLabel")
+      ),
       overrideDefFormat = compilerObj.flatMap(
         _.getStringOption("overrideDefFormat")
       ),
@@ -210,7 +213,6 @@ object InitializationOptions {
         compilerObj.flatMap(_.getBooleanOption("snippetAutoIndent")),
     )
   }
-
 }
 
 sealed trait CommandHTMLFormat {

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

@@ -225,7 +225,8 @@ object MetalsServerConfig {
         base.copy(
           executeClientCommand = ExecuteClientCommandConfig.on,
           compilers = base.compilers.copy(
-            snippetAutoIndent = false
+            snippetAutoIndent = false,
+            isDetailIncludedInLabel = false,
           ),
         )
       case _ =>

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

@@ -96,6 +96,13 @@ enum OverrideDefFormat {
 	 */
 	boolean isCompletionSnippetsEnabled();
 
+	/**
+	 * Returns true if the completion's description should be included in the label.
+	 */
+	default boolean isDetailIncludedInLabel() {
+    return true;
+  }
+
 	/**
 	 * The maximum delay for requests to respond.
 	 *

mtags-shared/src/main/scala/scala/meta/internal/pc/CompilerInitializationOptions.scala

@@ -16,6 +16,8 @@ package scala.meta.internal.pc
  * @param isHoverDocumentationEnabled whether to include docstrings in a `textDocument/hover`.
  * @param isSignatureHelpDocumentationEnabled whether the `SignatureHelp.documentation` field
  *                                            should be populated.
+ * @param isDetailIncludedInLabel whether the completion's description should be included in the
+ *                                label.
  * @param overrideDefFormat whether the override should include a unicode icon or only ascii.
  * @param parameterHintsCommand command identifier to trigger parameter hints.
  * @param snippetAutoIndent whether the client defaults to adding the indentation of the reference
@@ -28,6 +30,7 @@ case class CompilerInitializationOptions(
     isCompletionItemResolve: Option[Boolean],
     isHoverDocumentationEnabled: Option[Boolean],
     isSignatureHelpDocumentationEnabled: Option[Boolean],
+    isDetailIncludedInLabel: Option[Boolean],
     overrideDefFormat: Option[String],
     parameterHintsCommand: Option[String],
     snippetAutoIndent: Option[Boolean]
@@ -44,6 +47,7 @@ object CompilerInitializationOptions {
       None,
       None,
       None,
+      None,
       None
     )
 }

mtags-shared/src/main/scala/scala/meta/internal/pc/PresentationCompilerConfigImpl.scala

@@ -22,6 +22,7 @@ case class PresentationCompilerConfigImpl(
     snippetAutoIndent: Boolean = true,
     isSignatureHelpDocumentationEnabled: Boolean = true,
     isCompletionSnippetsEnabled: Boolean = true,
+    override val isDetailIncludedInLabel: Boolean = true,
     isCompletionItemResolve: Boolean = true,
     _isStripMarginOnTypeFormattingEnabled: () => Boolean = () => true,
     timeoutDelay: Long = 20,
@@ -72,6 +73,9 @@ case class PresentationCompilerConfigImpl(
       isCompletionItemResolve = options.isCompletionItemResolve.getOrElse(
         this.isCompletionItemResolve
       ),
+      isDetailIncludedInLabel = options.isDetailIncludedInLabel.getOrElse(
+        this.isDetailIncludedInLabel
+      ),
       _parameterHintsCommand = options.parameterHintsCommand.orElse(
         this._parameterHintsCommand
       ),

mtags/src/main/scala-2/scala/meta/internal/pc/CompletionProvider.scala

@@ -111,7 +111,9 @@ class CompletionProvider(
       }
 
       def labelWithSig =
-        if (member.sym.isMethod || member.sym.isValue) {
+        if (
+          compiler.metalsConfig.isDetailIncludedInLabel && (member.sym.isMethod || member.sym.isValue)
+        ) {
           ident + detail
         } else {
           ident

mtags/src/main/scala-3/scala/meta/internal/pc/completions/CompletionProvider.scala

@@ -162,7 +162,11 @@ class CompletionProvider(
     // related issue https://github.com/lampepfl/dotty/issues/11941
     lazy val kind: CompletionItemKind = completion.completionItemKind
     val description = completion.description(printer)
-    val label = completion.labelWithDescription(printer)
+    val label =
+      if config.isDetailIncludedInLabel then
+        completion.labelWithDescription(printer)
+      else
+        completion.label
     val ident = completion.insertText.getOrElse(completion.label)
 
     def mkItem(