fix(yaml): skip environment variable interpolation in YAML comments (#1361)

* Initial plan

* fix(yaml): skip environment variable interpolation in YAML comments

* style(yaml): apply biome linting fixes

Co-authored-by: quanru <11739753+quanru@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: quanru <11739753+quanru@users.noreply.github.com>

Author: Copilot

packages/core/src/yaml/utils.ts

@@ -11,13 +11,29 @@ import yaml from 'js-yaml';
 const debugUtils = getDebug('yaml:utils');
 
 export function interpolateEnvVars(content: string): string {
-  return content.replace(/\$\{([^}]+)\}/g, (_, envVar) => {
-    const value = process.env[envVar.trim()];
-    if (value === undefined) {
-      throw new Error(`Environment variable "${envVar.trim()}" is not defined`);
+  // Process line by line to skip commented lines
+  const lines = content.split('\n');
+  const processedLines = lines.map((line) => {
+    // Check if the line is a YAML comment (starts with # after optional whitespace)
+    const trimmedLine = line.trimStart();
+    if (trimmedLine.startsWith('#')) {
+      // Skip interpolation for comment lines
+      return line;
     }
-    return value;
+
+    // Process environment variables for non-comment lines
+    return line.replace(/\$\{([^}]+)\}/g, (_, envVar) => {
+      const value = process.env[envVar.trim()];
+      if (value === undefined) {
+        throw new Error(
+          `Environment variable "${envVar.trim()}" is not defined`,
+        );
+      }
+      return value;
+    });
   });
+
+  return processedLines.join('\n');
 }
 
 export function parseYamlScript(

packages/web-integration/tests/unit-test/yaml/utils.test.ts

@@ -53,6 +53,40 @@ tasks:
       );
     });
 
+    test('should not throw error for undefined env vars in commented lines', () => {
+      const yamlContent = `
+# DEV_USERNAME="\${UNDEFINED_ENV_VAR}"
+target:
+  url: "https://example.com"
+tasks:
+  - sleep: 1000
+  # - aiInput: "\${ANOTHER_UNDEFINED_VAR}"
+  #   locate: "input field"
+`;
+
+      expect(() => parseYamlScript(yamlContent)).not.toThrow();
+      const result = parseYamlScript(yamlContent);
+      expect(result.target?.url).toBe('https://example.com');
+    });
+
+    test('should handle mixed commented and uncommented env vars', () => {
+      process.env.DEFINED_VAR = 'defined_value';
+
+      const yamlContent = `
+# This is a comment with \${UNDEFINED_VAR_IN_COMMENT}
+target:
+  url: "https://example.com/\${DEFINED_VAR}"
+tasks:
+  - sleep: 1000
+  # - aiAction: "click \${UNDEFINED_IN_COMMENT}"
+`;
+
+      const result = parseYamlScript(yamlContent);
+      expect(result.target?.url).toBe('https://example.com/defined_value');
+
+      process.env.DEFINED_VAR = undefined;
+    });
+
     test('android number-style deviceId', () => {
       const yamlContent = `
 android: