fix: evaluateExpression returns empty string for empty steps/needs env vars in workflow_dispatch (#21633)

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: pelikhan <[email protected]>

Author: Copilot

actions/setup/js/runtime_import.cjs

@@ -277,7 +277,7 @@ function evaluateExpression(expr) {
     // e.g., "needs.search_issues.outputs.issue_list" → "GH_AW_NEEDS_SEARCH_ISSUES_OUTPUTS_ISSUE_LIST"
     const envVarName = "GH_AW_" + trimmed.toUpperCase().replace(/\./g, "_");
     const envValue = process.env[envVarName];
-    if (envValue !== undefined && envValue !== null && envValue !== "") {
+    if (envValue !== undefined && envValue !== null) {
       return envValue;
     }
     // If not found in environment, continue to try other evaluation methods below

actions/setup/js/runtime_import.test.cjs

@@ -768,6 +768,30 @@ describe("runtime_import", () => {
           expect(evaluateExpression("steps.test.outputs.result")).toContain("steps.test.outputs.result");
         });
 
+        it("should return empty string when env var is set to empty (e.g. workflow_dispatch with no text)", () => {
+          process.env.GH_AW_STEPS_SANITIZED_OUTPUTS_TEXT = "";
+          try {
+            expect(evaluateExpression("steps.sanitized.outputs.text")).toBe("");
+          } finally {
+            delete process.env.GH_AW_STEPS_SANITIZED_OUTPUTS_TEXT;
+          }
+        });
+
+        it("should return env var value for needs/steps expressions when set", () => {
+          process.env.GH_AW_STEPS_SANITIZED_OUTPUTS_TEXT = "Hello world";
+          try {
+            expect(evaluateExpression("steps.sanitized.outputs.text")).toBe("Hello world");
+          } finally {
+            delete process.env.GH_AW_STEPS_SANITIZED_OUTPUTS_TEXT;
+          }
+          process.env.GH_AW_NEEDS_BUILD_OUTPUTS_VERSION = "v1.2.3";
+          try {
+            expect(evaluateExpression("needs.build.outputs.version")).toBe("v1.2.3");
+          } finally {
+            delete process.env.GH_AW_NEEDS_BUILD_OUTPUTS_VERSION;
+          }
+        });
+
         it("should handle missing properties gracefully", () => {
           const result = evaluateExpression("github.event.nonexistent.property");
           expect(result).toContain("github.event.nonexistent.property");