fix register view error handling (fixes #316)

src/state/registers-view.ts

@@ -221,8 +221,15 @@ class RegisterTreeItem extends vscode.TreeItem implements vscode.Disposable {
 
   public async values() {
     if (this._values === undefined) {
-      this._values = this.register.get()
-        .then((values) => values?.map((v) => new ValueTreeItem(v)) ?? []);
+      this._values = (async () => {
+        try {
+          const values = await this.register.get();
+
+          return values?.map((v) => new ValueTreeItem(v)) ?? [];
+        } catch (e) {
+          return [new ValueTreeItem(`${e}`, "warning")];
+        }
+      })();
     }
 
     return await this._values;
@@ -234,10 +241,10 @@ class RegisterTreeItem extends vscode.TreeItem implements vscode.Disposable {
 }
 
 class ValueTreeItem extends vscode.TreeItem {
-  public constructor(label: string) {
+  public constructor(label: string, icon: string = "symbol-string") {
     super(label, vscode.TreeItemCollapsibleState.None);
 
-    this.iconPath = new vscode.ThemeIcon("symbol-string");
+    this.iconPath = new vscode.ThemeIcon(icon);
   }
 }
 

src/state/registers.ts

@@ -707,6 +707,19 @@ export abstract class RegisterSet implements vscode.Disposable {
  * The set of all registers linked to a specific document.
  */
 export class DocumentRegisters extends RegisterSet {
+  public override get registers(): Set<Register> {
+    const registers = super.registers;
+
+    // Remove special registers.
+    for (const register of registers) {
+      if (!(register instanceof GeneralPurposeRegister)) {
+        registers.delete(register);
+      }
+    }
+
+    return registers;
+  }
+
   public constructor(
     /**
      * The document to which the registers are linked.