From 8697631c8bfde10448ef23c026d01983b22b82e0 Mon Sep 17 00:00:00 2001
From: Pratik Dhanave <i.pratikdhanave@gmail.com>
Date: Sun, 1 Nov 2026 07:30:21 +0530
Subject: [PATCH] fix(cli): clear error for empty/comment-only scenario,
 persona, traits YAML

loadScenario/loadPersona/loadTraits in config-loader.ts dereference the parsed
YAML immediately (data.task, data.personality, ...). The yaml parser returns
null for an empty or comment-only file, so 'scope run' with such a
scenario/persona/traits file crashed with an opaque
'TypeError: Cannot read properties of null (reading "task")' instead of the
clear validation error each loader is written to raise.

Guard for a null/non-object parse result in all three loaders and raise the
loader's own validation message. Add config-loader.test.ts covering the empty
and comment-only cases plus a valid-scenario sanity check.
---
 apps/cli/src/config-loader.test.ts | 52 ++++++++++++++++++++++++++++++
 apps/cli/src/config-loader.ts      | 14 ++++++++
 2 files changed, 66 insertions(+)
 create mode 100644 apps/cli/src/config-loader.test.ts

diff --git a/apps/cli/src/config-loader.test.ts b/apps/cli/src/config-loader.test.ts
new file mode 100644
index 000000000..497b4db19
--- /dev/null
+++ b/apps/cli/src/config-loader.test.ts
@@ -0,0 +1,52 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+import { describe, it, expect, afterAll } from "vitest";
+import { writeFileSync, mkdtempSync, rmSync } from "node:fs";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
+
+import { resolveScenarioAndPersona } from "./config-loader.js";
+
+const dir = mkdtempSync(join(tmpdir(), "scope-config-loader-"));
+afterAll(() => rmSync(dir, { recursive: true, force: true }));
+
+function write(name: string, content: string): string {
+  const path = join(dir, name);
+  writeFileSync(path, content, "utf-8");
+  return path;
+}
+
+const validScenario = write(
+  "scenario.yaml",
+  'task: "summarize the file"\ncriteria:\n  - correctness\n'
+);
+
+describe("resolveScenarioAndPersona config validation", () => {
+  it("reports a clear error for an empty scenario file (not a TypeError)", () => {
+    const scenario = write("empty-scenario.yaml", "");
+    expect(() => resolveScenarioAndPersona(scenario)).toThrowError(
+      /must have a "task" string field/
+    );
+  });
+
+  it("reports a clear error for a comment-only scenario file", () => {
+    const scenario = write("comment-scenario.yaml", "# nothing here\n");
+    expect(() => resolveScenarioAndPersona(scenario)).toThrowError(
+      /must have a "task" string field/
+    );
+  });
+
+  it("reports a clear error for a comment-only persona file (not a TypeError)", () => {
+    const persona = write("comment-persona.yaml", "# just a comment\n");
+    expect(() => resolveScenarioAndPersona(validScenario, persona)).toThrowError(
+      /is empty or not a YAML mapping/
+    );
+  });
+
+  it("still loads a valid scenario without a persona", () => {
+    const result = resolveScenarioAndPersona(validScenario);
+    expect(result.task).toBe("summarize the file");
+    expect(result.criteria).toEqual(["correctness"]);
+  });
+});
diff --git a/apps/cli/src/config-loader.ts b/apps/cli/src/config-loader.ts
index 425cb0cd8..0db371662 100644
--- a/apps/cli/src/config-loader.ts
+++ b/apps/cli/src/config-loader.ts
@@ -37,6 +37,10 @@ function loadPersona(filePath: string): Persona {
   const raw = readFileSync(filePath, "utf-8");
   const data = parseYaml(raw);
 
+  if (!data || typeof data !== "object") {
+    throw new Error(`Persona file ${filePath} is empty or not a YAML mapping`);
+  }
+
   const validPersonality: Personality[] = ["demanding", "friendly"];
   const validExperience: Experience[] = ["junior", "senior"];
   const validVerbosity: Verbosity[] = ["brief", "moderate"];
@@ -75,6 +79,10 @@ function loadScenario(filePath: string): Scenario {
   const raw = readFileSync(filePath, "utf-8");
   const data = parseYaml(raw);
 
+  if (!data || typeof data !== "object") {
+    throw new Error(`Scenario file ${filePath} must have a "task" string field`);
+  }
+
   if (!data.task || typeof data.task !== "string") {
     throw new Error(`Scenario file ${filePath} must have a "task" string field`);
   }
@@ -108,6 +116,12 @@ function loadTraits(filePath: string): TraitDescriptions {
   const raw = readFileSync(filePath, "utf-8");
   const data = parseYaml(raw);
 
+  if (!data || typeof data !== "object") {
+    throw new Error(
+      `Traits file ${filePath} must have personality, experience, verbosity, and type sections`
+    );
+  }
+
   if (!data.personality || !data.experience || !data.verbosity || !data.type) {
     throw new Error(
       `Traits file ${filePath} must have personality, experience, verbosity, and type sections`