feat: add class for ToolCheckResult

it is now easier to check if it's an error or not

src/formatters.ts

@@ -1,5 +1,5 @@
 import * as vscode from "vscode";
-import { checkHasError, extensionConfiguration, getOutputChannel } from "./utils";
+import { extensionConfiguration, getOutputChannel } from "./utils";
 import { ToolCheckFunc, Tool } from "./types";
 import * as muon from "./tools/muon";
 
@@ -28,7 +28,7 @@ async function reloadFormatters(sourceRoot: string, context: vscode.ExtensionCon
   const props = formatters[name];
 
   const checkResult = await props.check();
-  if (checkHasError(checkResult)) {
+  if (checkResult.isError()) {
     getOutputChannel().appendLine(`Failed to enable formatter ${name}: ${checkResult.error}`);
     getOutputChannel().show(true);
     return disposables;

src/linters.ts

@@ -1,5 +1,5 @@
 import * as vscode from "vscode";
-import { checkHasError, extensionConfiguration, getOutputChannel } from "./utils";
+import { extensionConfiguration, getOutputChannel } from "./utils";
 import { ExtensionConfiguration, LinterConfiguration, ToolCheckFunc, Tool } from "./types";
 import * as muon from "./tools/muon";
 
@@ -39,7 +39,7 @@ async function reloadLinters(
 
     const props = linters[name];
     const checkResult = await props.check();
-    if (checkHasError(checkResult)) {
+    if (checkResult.isError()) {
       getOutputChannel().appendLine(`Failed to enable linter ${name}: ${checkResult.error}`);
       getOutputChannel().show(true);
       continue;

src/tools/muon.ts

@@ -1,6 +1,6 @@
 import * as vscode from "vscode";
 import { ExecResult, exec, execFeed, extensionConfiguration, getOutputChannel } from "../utils";
-import { Tool, type ToolCheckResult } from "../types";
+import { Tool, ToolCheckResult } from "../types";
 import { Version, type VersionArray } from "../version";
 
 export async function lint(muon: Tool, root: string, document: vscode.TextDocument): Promise<vscode.Diagnostic[]> {
@@ -91,12 +91,12 @@ export async function check(): Promise<ToolCheckResult> {
   } catch (e) {
     const { error, stdout, stderr } = e as ExecResult;
     console.log(error);
-    return { error: error!.message };
+    return ToolCheckResult.newError(error!.message);
   }
 
   const line1 = stdout.split("\n")[0].split(" ");
   if (line1.length !== 2) {
-    return { error: `Invalid version string: ${line1}` };
+    return ToolCheckResult.newError(`Invalid version string: ${line1}`);
   }
 
   const ver = line1[1]
@@ -110,5 +110,5 @@ export async function check(): Promise<ToolCheckResult> {
       return Number.parseInt(s);
     }) as VersionArray;
 
-  return { tool: { path: muon_path, version: new Version(ver) } };
+  return ToolCheckResult.newTool({ path: muon_path, version: new Version(ver) });
 }

src/types.ts

@@ -14,7 +14,46 @@ export type ToolCheckErrorResult = {
   error: string;
 };
 
-export type ToolCheckResult = ToolCheckSuccessResult | ToolCheckErrorResult;
+type ResultImpl = ToolCheckSuccessResult | ToolCheckErrorResult;
+
+export class ToolCheckResult {
+  private readonly result: ResultImpl;
+
+  private constructor(result: ResultImpl) {
+    this.result = result;
+  }
+
+  static newError(error: string) {
+    return new ToolCheckResult({ error });
+  }
+
+  static newTool(tool: Tool) {
+    return new ToolCheckResult({ tool });
+  }
+
+  private hasErrorImpl(result: ResultImpl): result is ToolCheckErrorResult {
+    return !!result.error;
+  }
+
+  isError(): boolean {
+    return this.hasErrorImpl(this.result);
+  }
+
+  get error(): string {
+    if (!this.hasErrorImpl(this.result)) {
+      throw new Error("Wrong invocation of getter for 'error', check the state first");
+    }
+    return this.result.error;
+  }
+
+  get tool(): Tool {
+    if (this.hasErrorImpl(this.result)) {
+      throw new Error("Wrong invocation of getter for 'tool', check the state first");
+    }
+    return this.result.tool;
+  }
+}
+
 export type ToolCheckFunc = () => Promise<ToolCheckResult>;
 
 export type LinterConfiguration = {

src/utils.ts

@@ -216,7 +216,3 @@ export function whenFileExists(ctx: vscode.ExtensionContext, file: string, liste
 export function mesonProgram(): string {
   return which.sync(extensionConfiguration("mesonPath"));
 }
-
-export function checkHasError(result: ToolCheckResult): result is ToolCheckErrorResult {
-  return !!result.error;
-}