Add latest-known version selector (#993)

## Summary

- add `latest-known` as an explicit version selector
- resolve it locally to the newest version in the bundled checksum table
- preserve existing default and `latest` behavior
- document custom-manifest checksum semantics and update published
bundles

## Testing

- `npm ci --ignore-scripts`
- `npm run all` (99 tests passed)

Closes #919

Refs: pi-session 019fed0e-6019-7504-911b-bd9955cbbd49

src/download/checksum/known-version.ts

@@ -0,0 +1,23 @@
+import * as semver from "semver";
+import { KNOWN_CHECKSUMS } from "./known-checksums";
+
+const VERSION_IN_CHECKSUM_KEY_PATTERN =
+  /-(\d+\.\d+\.\d+(?:[-+][0-9A-Za-z.-]+)?)$/;
+
+export function getLatestKnownVersion(): string {
+  const versions = new Set<string>();
+
+  for (const key of Object.keys(KNOWN_CHECKSUMS)) {
+    const version = key.match(VERSION_IN_CHECKSUM_KEY_PATTERN)?.[1];
+    if (version !== undefined) {
+      versions.add(version);
+    }
+  }
+
+  const latestVersion = [...versions].sort(semver.rcompare)[0];
+  if (!latestVersion) {
+    throw new Error("Could not determine latest known version from checksums.");
+  }
+
+  return latestVersion;
+}

src/update-known-checksums.ts

@@ -1,6 +1,6 @@
 import * as core from "@actions/core";
 import * as semver from "semver";
-import { KNOWN_CHECKSUMS } from "./download/checksum/known-checksums";
+import { getLatestKnownVersion } from "./download/checksum/known-version";
 import {
   type ChecksumEntry,
   updateChecksums,
@@ -12,9 +12,6 @@ import {
 } from "./download/manifest";
 import * as log from "./utils/logging";
 
-const VERSION_IN_CHECKSUM_KEY_PATTERN =
-  /-(\d+\.\d+\.\d+(?:[-+][0-9A-Za-z.-]+)?)$/;
-
 async function run(): Promise<void> {
   const checksumFilePath = process.argv.slice(2)[0];
   if (!checksumFilePath) {
@@ -24,7 +21,7 @@ async function run(): Promise<void> {
   }
 
   const latestVersion = await getLatestVersion();
-  const latestKnownVersion = getLatestKnownVersionFromChecksums();
+  const latestKnownVersion = getLatestKnownVersion();
 
   if (semver.lte(latestVersion, latestKnownVersion)) {
     log.info(
@@ -40,28 +37,6 @@ async function run(): Promise<void> {
   core.setOutput("latest-version", latestVersion);
 }
 
-function getLatestKnownVersionFromChecksums(): string {
-  const versions = new Set<string>();
-
-  for (const key of Object.keys(KNOWN_CHECKSUMS)) {
-    const version = extractVersionFromChecksumKey(key);
-    if (version !== undefined) {
-      versions.add(version);
-    }
-  }
-
-  const latestVersion = [...versions].sort(semver.rcompare)[0];
-  if (!latestVersion) {
-    throw new Error("Could not determine latest known version from checksums.");
-  }
-
-  return latestVersion;
-}
-
-function extractVersionFromChecksumKey(key: string): string | undefined {
-  return key.match(VERSION_IN_CHECKSUM_KEY_PATTERN)?.[1];
-}
-
 function extractChecksumsFromManifest(
   versions: ManifestVersion[],
 ): ChecksumEntry[] {

src/version/resolve.ts

@@ -2,6 +2,7 @@ import * as core from "@actions/core";
 import * as tc from "@actions/tool-cache";
 import * as pep440 from "@renovatebot/pep440";
 import * as semver from "semver";
+import { getLatestKnownVersion } from "../download/checksum/known-version";
 import {
   getAllVersions,
   getFirstMatchingVersion,
@@ -143,6 +144,10 @@ export async function resolveVersion(
 ): Promise<string> {
   core.debug(`Resolving version: ${versionInput}`);
 
+  if (versionInput.trim() === "latest-known") {
+    return getLatestKnownVersion();
+  }
+
   const context: ConcreteVersionResolutionContext = {
     manifestUrl,
     parsedSpecifier: parseVersionSpecifier(versionInput),