Add resolved Python version output for activated environments

.github/workflows/test.yml

@@ -347,9 +347,14 @@ jobs:
           if [ "$PYTHON_VERSION" != "3.13.1t" ]; then
             exit 1
           fi
+          if [ -n "$PYTHON_VERSION_RESOLVED" ]; then
+            echo "python-version-resolved should be empty without environment activation"
+            exit 1
+          fi
         shell: bash
         env:
           PYTHON_VERSION: ${{ steps.setup-uv.outputs.python-version }}
+          PYTHON_VERSION_RESOLVED: ${{ steps.setup-uv.outputs.python-version-resolved }}
       - run: uv sync
         working-directory: __tests__/fixtures/uv-project
 
@@ -358,23 +363,46 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
+        python-version: ["3.13.1t"]
+        include:
+          - os: ubuntu-latest
+            python-version: "3.13"
+          - os: ubuntu-latest
+            python-version: "3.14.0rc2"
+          - os: ubuntu-latest
+            python-version: "pypy3.11"
     steps:
       - name: Install latest version
         id: setup-uv
         uses: $/
         with:
-          python-version: 3.13.1t
+          python-version: ${{ matrix.python-version }}
           activate-environment: true
+          enable-cache: true
       - name: Verify packages can be installed
         run: uv pip install pip
         shell: bash
-      - name: Verify python version is correct
+      - name: Verify Python version outputs and cache key
         run: |
-          python --version
-          if [ "$(python --version)" != "Python 3.13.1" ]; then
+          expected=$(python -I -c 'import platform; print(platform.python_version())')
+          if [ "$PYTHON_VERSION_RESOLVED" != "$expected" ]; then
+            echo "Wrong resolved Python version: $PYTHON_VERSION_RESOLVED (expected $expected)"
             exit 1
           fi
+          if [ "$PYTHON_VERSION" != "$PYTHON_REQUEST" ]; then
+            echo "Wrong requested Python version: $PYTHON_VERSION"
+            exit 1
+          fi
+          case "$CACHE_KEY" in
+            *-"$PYTHON_REQUEST"-*) ;;
+            *) echo "Cache key no longer contains requested Python version: $CACHE_KEY"; exit 1 ;;
+          esac
         shell: bash
+        env:
+          CACHE_KEY: ${{ steps.setup-uv.outputs.cache-key }}
+          PYTHON_REQUEST: ${{ matrix.python-version }}
+          PYTHON_VERSION: ${{ steps.setup-uv.outputs.python-version }}
+          PYTHON_VERSION_RESOLVED: ${{ steps.setup-uv.outputs.python-version-resolved }}
       - name: Verify output venv is set
         run: |
           if [ -z "$UV_VENV" ]; then
@@ -439,6 +467,15 @@ jobs:
               raise SystemExit(f"Python is not running from custom venv: {sys.executable}")
           PY
         shell: bash
+      - name: Verify resolved Python version from custom venv
+        run: |
+          if [ "$PYTHON_VERSION_RESOLVED" != "3.13.1" ]; then
+            echo "Wrong resolved Python version: $PYTHON_VERSION_RESOLVED"
+            exit 1
+          fi
+        shell: bash
+        env:
+          PYTHON_VERSION_RESOLVED: ${{ steps.setup-uv.outputs.python-version-resolved }}
 
   test-activate-environment-no-project:
     runs-on: ubuntu-latest

README.md

@@ -138,6 +138,8 @@ Have a look under [Advanced Configuration](#advanced-configuration) for detailed
 - `cache-hit`: A boolean value to indicate a cache entry was found.
 - `venv`: Path to the activated venv if activate-environment is true.
 - `python-version`: The Python version that was set.
+- `python-version-resolved`: The full Python version of the activated venv, including prerelease suffixes.
+  Empty when `activate-environment` is false or the version cannot be determined.
 - `python-cache-hit`: A boolean value to indicate the Python cache entry was found.
 
 ### Python version

__tests__/utils/python-version.test.ts

@@ -0,0 +1,131 @@
+import * as path from "node:path";
+import type * as exec from "@actions/exec";
+import {
+  afterEach,
+  beforeEach,
+  describe,
+  expect,
+  it,
+  jest,
+} from "@jest/globals";
+import { createSetupInputs } from "../helpers/setup-inputs";
+
+const mockGetExecOutput = jest.fn<typeof exec.getExecOutput>();
+const mockDebug = jest.fn();
+const originalPlatform = process.platform;
+
+jest.unstable_mockModule("@actions/core", () => ({
+  debug: mockDebug,
+  isDebug: jest.fn(() => false),
+}));
+
+jest.unstable_mockModule("@actions/exec", () => ({
+  getExecOutput: mockGetExecOutput,
+}));
+
+const { getResolvedPythonVersion } = await import(
+  "../../src/utils/python-version"
+);
+
+beforeEach(() => {
+  mockGetExecOutput.mockReset();
+});
+
+afterEach(() => {
+  Object.defineProperty(process, "platform", { value: originalPlatform });
+});
+
+describe("getResolvedPythonVersion", () => {
+  it("does not query Python when environment activation is disabled", async () => {
+    const inputs = createSetupInputs({ pythonVersion: "3.15t" });
+
+    expect(await getResolvedPythonVersion(inputs)).toBe("");
+    expect(mockGetExecOutput).not.toHaveBeenCalled();
+  });
+
+  it.each([
+    ["3.13", "3.13.1"],
+    ["3.13.1t", "3.13.1"],
+    ["3.15t", "3.15.0rc1"],
+    ["pypy3.11", "3.11.11"],
+    ["", "3.12.9"],
+  ])(
+    "resolves %j to the interpreter's version %s",
+    async (request, version) => {
+      mockGetExecOutput.mockResolvedValue({
+        exitCode: 0,
+        stderr: "",
+        stdout: `${version}\r\n`,
+      });
+      const inputs = createSetupInputs({
+        activateEnvironment: true,
+        pythonVersion: request,
+      });
+
+      expect(await getResolvedPythonVersion(inputs)).toBe(version);
+      expect(inputs.pythonVersion).toBe(request);
+    },
+  );
+
+  it.each(["linux", "darwin", "win32"])(
+    "queries the custom venv directly on %s, including paths with spaces",
+    async (platform) => {
+      Object.defineProperty(process, "platform", { value: platform });
+      mockGetExecOutput.mockResolvedValue({
+        exitCode: 0,
+        stderr: "",
+        stdout: "3.13.1\n",
+      });
+      const inputs = createSetupInputs({
+        activateEnvironment: true,
+        venvPath: "/runner temp/custom venv",
+        workingDirectory: "/different/project",
+      });
+
+      await getResolvedPythonVersion(inputs);
+
+      const pythonPath =
+        platform === "win32"
+          ? path.join(inputs.venvPath, "Scripts", "python.exe")
+          : path.join(inputs.venvPath, "bin", "python");
+      expect(mockGetExecOutput).toHaveBeenCalledWith(
+        `"${pythonPath}"`,
+        ["-I", "-c", "import platform; print(platform.python_version())"],
+        { silent: true },
+      );
+    },
+  );
+
+  it("escapes quotes in the venv path for @actions/exec", async () => {
+    Object.defineProperty(process, "platform", { value: "linux" });
+    mockGetExecOutput.mockResolvedValue({
+      exitCode: 0,
+      stderr: "",
+      stdout: "3.13.1\n",
+    });
+    const inputs = createSetupInputs({
+      activateEnvironment: true,
+      venvPath: '/workspace/a "quoted" venv',
+    });
+
+    await getResolvedPythonVersion(inputs);
+
+    expect(mockGetExecOutput.mock.calls[0][0]).toContain('a \\"quoted\\" venv');
+  });
+
+  it.each([new Error("interpreter missing"), "interpreter failed"])(
+    "returns an empty output if the interpreter cannot be queried: %s",
+    async (error) => {
+      mockGetExecOutput.mockRejectedValue(error);
+
+      expect(
+        await getResolvedPythonVersion(
+          createSetupInputs({ activateEnvironment: true }),
+        ),
+      ).toBe("");
+      expect(mockDebug).toHaveBeenCalledWith(
+        expect.stringContaining(error instanceof Error ? error.message : error),
+      );
+    },
+  );
+});

action-types.yml

@@ -79,5 +79,7 @@ outputs:
     type: string
   python-version:
     type: string
+  python-version-resolved:
+    type: string
   python-cache-hit:
     type: boolean

action.yml

@@ -107,6 +107,8 @@ outputs:
     description: "Path to the activated venv if activate-environment is true"
   python-version:
     description: "The Python version that was set."
+  python-version-resolved:
+    description: "The full Python version of the activated venv, including prerelease suffixes. Empty when activate-environment is false or the version cannot be determined."
   python-cache-hit:
     description: "A boolean value to indicate the Python cache entry was found"
 runs:

dist/setup/index.cjs

@@ -14676,7 +14676,7 @@ var require_util4 = __commonJS({
     var { getEncoding } = require_encoding();
     var { serializeAMimeType, parseMIMEType } = require_data_url();
     var { types: types2 } = require("node:util");
-    var { StringDecoder } = require("string_decoder");
+    var { StringDecoder: StringDecoder2 } = require("string_decoder");
     var { btoa: btoa2 } = require("node:buffer");
     var staticPropertyDescriptors = {
       enumerable: true,
@@ -14767,7 +14767,7 @@ var require_util4 = __commonJS({
             dataURL += serializeAMimeType(parsed);
           }
           dataURL += ";base64,";
-          const decoder = new StringDecoder("latin1");
+          const decoder = new StringDecoder2("latin1");
           for (const chunk of bytes) {
             dataURL += btoa2(decoder.write(chunk));
           }
@@ -14796,7 +14796,7 @@ var require_util4 = __commonJS({
         }
         case "BinaryString": {
           let binaryString = "";
-          const decoder = new StringDecoder("latin1");
+          const decoder = new StringDecoder2("latin1");
           for (const chunk of bytes) {
             binaryString += decoder.write(chunk);
           }
@@ -58186,6 +58186,9 @@ var _summary = new Summary();
 // node_modules/@actions/core/lib/platform.js
 var import_os2 = __toESM(require("os"), 1);
 
+// node_modules/@actions/exec/lib/exec.js
+var import_string_decoder = require("string_decoder");
+
 // node_modules/@actions/exec/lib/toolrunner.js
 var os3 = __toESM(require("os"), 1);
 var events = __toESM(require("events"), 1);
@@ -59006,6 +59009,38 @@ function exec(commandLine, args, options) {
     return runner.exec();
   });
 }
+function getExecOutput(commandLine, args, options) {
+  return __awaiter7(this, void 0, void 0, function* () {
+    var _a2, _b;
+    let stdout = "";
+    let stderr = "";
+    const stdoutDecoder = new import_string_decoder.StringDecoder("utf8");
+    const stderrDecoder = new import_string_decoder.StringDecoder("utf8");
+    const originalStdoutListener = (_a2 = options === null || options === void 0 ? void 0 : options.listeners) === null || _a2 === void 0 ? void 0 : _a2.stdout;
+    const originalStdErrListener = (_b = options === null || options === void 0 ? void 0 : options.listeners) === null || _b === void 0 ? void 0 : _b.stderr;
+    const stdErrListener = (data) => {
+      stderr += stderrDecoder.write(data);
+      if (originalStdErrListener) {
+        originalStdErrListener(data);
+      }
+    };
+    const stdOutListener = (data) => {
+      stdout += stdoutDecoder.write(data);
+      if (originalStdoutListener) {
+        originalStdoutListener(data);
+      }
+    };
+    const listeners = Object.assign(Object.assign({}, options === null || options === void 0 ? void 0 : options.listeners), { stdout: stdOutListener, stderr: stdErrListener });
+    const exitCode = yield exec(commandLine, args, Object.assign(Object.assign({}, options), { listeners }));
+    stdout += stdoutDecoder.end();
+    stderr += stderrDecoder.end();
+    return {
+      exitCode,
+      stdout,
+      stderr
+    };
+  });
+}
 
 // node_modules/@actions/core/lib/platform.js
 var platform = import_os2.default.platform();
@@ -102066,6 +102101,28 @@ function getResolutionStrategy() {
   );
 }
 
+// src/utils/python-version.ts
+var import_node_path2 = require("node:path");
+async function getResolvedPythonVersion(inputs) {
+  if (!inputs.activateEnvironment) {
+    return "";
+  }
+  const pythonPath = process.platform === "win32" ? (0, import_node_path2.join)(inputs.venvPath, "Scripts", "python.exe") : (0, import_node_path2.join)(inputs.venvPath, "bin", "python");
+  try {
+    const { stdout } = await getExecOutput(
+      `"${pythonPath.replace(/"/g, '\\"')}"`,
+      ["-I", "-c", "import platform; print(platform.python_version())"],
+      { silent: !isDebug() }
+    );
+    return stdout.trim();
+  } catch (error2) {
+    debug(
+      `Failed to get the activated environment's Python version. Error: ${error2 instanceof Error ? error2.message : String(error2)}`
+    );
+    return "";
+  }
+}
+
 // src/setup-uv.ts
 var sourceDir = __dirname;
 function formatUnexpectedFailure(error2) {
@@ -102136,6 +102193,10 @@ async function run() {
     info2(`Successfully installed uv version ${setupResult.version}`);
     const detectedPythonVersion = await getPythonVersion2(inputs);
     setOutput("python-version", detectedPythonVersion);
+    setOutput(
+      "python-version-resolved",
+      await getResolvedPythonVersion(inputs)
+    );
     if (inputs.enableCache) {
       await restoreCache2(inputs, detectedPythonVersion);
     }

docs/environment-and-tools.md

@@ -17,6 +17,19 @@ This allows directly using it in later steps:
 
 By default, the venv is created at `.venv` inside the `working-directory`.
 
+With `activate-environment: true`, the `python-version-resolved` output contains the
+venv's full Python version, as reported by `platform.python_version()`. For example,
+a `python-version` input of `3.15t` can resolve to `3.15.0rc1`. Use
+`${{ steps.setup-uv.outputs.python-version-resolved }}` in later steps to access
+the resolved version (with `id: setup-uv` on the setup step).
+
+This is the Python language version: it includes prerelease suffixes, but no
+implementation name or free-threaded marker. For cache keys that distinguish PyPy
+from CPython or free-threaded builds, include the requested version as well.
+The output is empty when `activate-environment` is false or the version cannot be
+determined. The existing `python-version` output and setup-uv's cache keys are
+unaffected.
+
 You can customize the venv location with `venv-path`, for example to place it in the runner temp directory:
 
 ```yaml

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 "";
+  }
+}