Add resolved Python version output for activated environments

src/setup-uv.ts

@@ -16,6 +16,7 @@ import {
   getPlatform,
   type Platform,
 } from "./utils/platforms";
+import { getResolvedPythonVersion } from "./utils/python-version";
 import { resolveUvVersion } from "./version/resolve";
 
 const sourceDir = __dirname;
@@ -101,6 +102,10 @@ async function run(): Promise<void> {
 
     const detectedPythonVersion = await getPythonVersion(inputs);
     core.setOutput("python-version", detectedPythonVersion);
+    core.setOutput(
+      "python-version-resolved",
+      await getResolvedPythonVersion(inputs),
+    );
 
     if (inputs.enableCache) {
       await restoreCache(inputs, detectedPythonVersion);

src/utils/python-version.ts

@@ -0,0 +1,32 @@
+import { join } from "node:path";
+import * as core from "@actions/core";
+import * as exec from "@actions/exec";
+import type { SetupInputs } from "./inputs";
+
+export async function getResolvedPythonVersion(
+  inputs: SetupInputs,
+): Promise<string> {
+  if (!inputs.activateEnvironment) {
+    return "";
+  }
+
+  const pythonPath =
+    process.platform === "win32"
+      ? join(inputs.venvPath, "Scripts", "python.exe")
+      : join(inputs.venvPath, "bin", "python");
+
+  try {
+    // @actions/exec parses the executable as a command line, so quote the path.
+    const { stdout } = await exec.getExecOutput(
+      `"${pythonPath.replace(/"/g, '\\"')}"`,
+      ["-I", "-c", "import platform; print(platform.python_version())"],
+      { silent: !core.isDebug() },
+    );
+    return stdout.trim();
+  } catch (error) {
+    core.debug(
+      `Failed to get the activated environment's Python version. Error: ${error instanceof Error ? error.message : String(error)}`,
+    );
+    return "";
+  }
+}