feature: fallback to pre-release when no stable version is found (#414)

This allows to specify version like `3.11` or `pypy3.10` in workflows before those versions are released.
This lessen the burden for users of `setup-python` by not having to modify their workflow twice: once when a pre-release is available (e.g. `3.11-dev`) and once when the first stable release is published (e.g. `3.11`)

src/find-pypy.ts

@@ -23,7 +23,8 @@ export async function findPyPyVersion(
   versionSpec: string,
   architecture: string,
   updateEnvironment: boolean,
-  checkLatest: boolean
+  checkLatest: boolean,
+  allowPreReleases: boolean
 ): Promise<{resolvedPyPyVersion: string; resolvedPythonVersion: string}> {
   let resolvedPyPyVersion = '';
   let resolvedPythonVersion = '';
@@ -39,7 +40,8 @@ export async function findPyPyVersion(
         releases,
         pypyVersionSpec.pythonVersion,
         pypyVersionSpec.pypyVersion,
-        architecture
+        architecture,
+        false
       );
 
       if (releaseData) {
@@ -71,6 +73,7 @@ export async function findPyPyVersion(
       pypyVersionSpec.pypyVersion,
       pypyVersionSpec.pythonVersion,
       architecture,
+      allowPreReleases,
       releases
     ));
   }

src/find-python.ts

@@ -34,11 +34,15 @@ export async function useCpythonVersion(
   version: string,
   architecture: string,
   updateEnvironment: boolean,
-  checkLatest: boolean
+  checkLatest: boolean,
+  allowPreReleases: boolean
 ): Promise<InstalledVersion> {
   let manifest: tc.IToolRelease[] | null = null;
   const desugaredVersionSpec = desugarDevVersion(version);
-  let semanticVersionSpec = pythonVersionToSemantic(desugaredVersionSpec);
+  let semanticVersionSpec = pythonVersionToSemantic(
+    desugaredVersionSpec,
+    allowPreReleases
+  );
   core.debug(`Semantic version spec of ${version} is ${semanticVersionSpec}`);
 
   if (checkLatest) {
@@ -178,8 +182,18 @@ interface InstalledVersion {
  * Python's prelease versions look like `3.7.0b2`.
  * This is the one part of Python versioning that does not look like semantic versioning, which specifies `3.7.0-b2`.
  * If the version spec contains prerelease versions, we need to convert them to the semantic version equivalent.
+ *
+ * For easier use of the action, we also map 'x.y' to allow pre-release before 'x.y.0' release if allowPreReleases is true
  */
-export function pythonVersionToSemantic(versionSpec: string) {
+export function pythonVersionToSemantic(
+  versionSpec: string,
+  allowPreReleases: boolean
+) {
   const prereleaseVersion = /(\d+\.\d+\.\d+)((?:a|b|rc)\d*)/g;
-  return versionSpec.replace(prereleaseVersion, '$1-$2');
+  const majorMinor = /^(\d+)\.(\d+)$/;
+  let result = versionSpec.replace(prereleaseVersion, '$1-$2');
+  if (allowPreReleases) {
+    result = result.replace(majorMinor, '~$1.$2.0-0');
+  }
+  return result;
 }

src/install-pypy.ts

@@ -1,3 +1,4 @@
+import * as os from 'os';
 import * as path from 'path';
 import * as core from '@actions/core';
 import * as tc from '@actions/tool-cache';
@@ -19,6 +20,7 @@ export async function installPyPy(
   pypyVersion: string,
   pythonVersion: string,
   architecture: string,
+  allowPreReleases: boolean,
   releases: IPyPyManifestRelease[] | undefined
 ) {
   let downloadDir;
@@ -29,13 +31,31 @@ export async function installPyPy(
     throw new Error('No release was found in PyPy version.json');
   }
 
-  const releaseData = findRelease(
+  let releaseData = findRelease(
     releases,
     pythonVersion,
     pypyVersion,
-    architecture
+    architecture,
+    false
   );
 
+  if (allowPreReleases && (!releaseData || !releaseData.foundAsset)) {
+    // check for pre-release
+    core.info(
+      [
+        `Stable PyPy version ${pythonVersion} (${pypyVersion}) with arch ${architecture} not found`,
+        `Trying pre-release versions`
+      ].join(os.EOL)
+    );
+    releaseData = findRelease(
+      releases,
+      pythonVersion,
+      pypyVersion,
+      architecture,
+      true
+    );
+  }
+
   if (!releaseData || !releaseData.foundAsset) {
     throw new Error(
       `PyPy version ${pythonVersion} (${pypyVersion}) with arch ${architecture} not found`
@@ -162,8 +182,10 @@ export function findRelease(
   releases: IPyPyManifestRelease[],
   pythonVersion: string,
   pypyVersion: string,
-  architecture: string
+  architecture: string,
+  includePrerelease: boolean
 ) {
+  const options = {includePrerelease: includePrerelease};
   const filterReleases = releases.filter(item => {
     const isPythonVersionSatisfied = semver.satisfies(
       semver.coerce(item.python_version)!,
@@ -173,7 +195,11 @@ export function findRelease(
       isNightlyKeyword(pypyVersion) && isNightlyKeyword(item.pypy_version);
     const isPyPyVersionSatisfied =
       isPyPyNightly ||
-      semver.satisfies(pypyVersionToSemantic(item.pypy_version), pypyVersion);
+      semver.satisfies(
+        pypyVersionToSemantic(item.pypy_version),
+        pypyVersion,
+        options
+      );
     const isArchPresent =
       item.files &&
       (IS_WINDOWS

src/setup-python.ts

@@ -77,6 +77,7 @@ async function run() {
   try {
     const versions = resolveVersionInput();
     const checkLatest = core.getBooleanInput('check-latest');
+    const allowPreReleases = core.getBooleanInput('allow-prereleases');
 
     if (versions.length) {
       let pythonVersion = '';
@@ -89,7 +90,8 @@ async function run() {
             version,
             arch,
             updateEnvironment,
-            checkLatest
+            checkLatest,
+            allowPreReleases
           );
           pythonVersion = `${installed.resolvedPyPyVersion}-${installed.resolvedPythonVersion}`;
           core.info(
@@ -100,7 +102,8 @@ async function run() {
             version,
             arch,
             updateEnvironment,
-            checkLatest
+            checkLatest,
+            allowPreReleases
           );
           pythonVersion = installed.version;
           core.info(`Successfully set up ${installed.impl} (${pythonVersion})`);