Merge f75efb3f19 into fba3fb4ead

README.md

@@ -44,6 +44,11 @@ See [action.yml](action.yml).
     # Note: if both go-version and go-version-file are provided, go-version takes precedence.
     go-version-file: 'go.mod'
     
+    # How to interpret an exact version read from go-version-file.
+    # Set to latest-patch to use the newest patch release of the same minor version.
+    # Default: exact
+    go-version-file-behavior: 'exact'
+    
     # Set this option if you want the action to check for the latest available version
     # Default: false
     check-latest: false

__tests__/setup-go.test.ts

@@ -1089,6 +1089,186 @@ use .
     );
   });
 
+  describe('go-version-file-behavior', () => {
+    const buildGoMod = (goVersion: string) => `module example.com/mymodule
+
+go ${goVersion}
+`;
+
+    it('resolves the latest patch of the minor with latest-patch', async () => {
+      os.platform = 'linux';
+      os.arch = 'x64';
+
+      inputs['go-version-file'] = 'go.mod';
+      inputs['go-version-file-behavior'] = 'latest-patch';
+      inputs['token'] = 'faketoken';
+      existsSpy.mockImplementation(() => true);
+      readFileSpy.mockImplementation(() => Buffer.from(buildGoMod('1.12.16')));
+
+      const expectedUrl =
+        'https://github.com/actions/go-versions/releases/download/1.12.17-20200616.21/go-1.12.17-linux-x64.tar.gz';
+
+      // ... but not in the local cache
+      findSpy.mockImplementation(() => '');
+
+      dlSpy.mockImplementation(async () => '/some/temp/path');
+      const toolPath = path.normalize('/cache/go/1.12.17/x64');
+      extractTarSpy.mockImplementation(async () => '/some/other/temp/path');
+      cacheSpy.mockImplementation(async () => toolPath);
+
+      await main.run();
+
+      expect(logSpy).toHaveBeenCalledWith(
+        'Using latest patch release satisfying ~1.12.16 (version file specifies 1.12.16)'
+      );
+      expect(logSpy).toHaveBeenCalledWith('Setup go version spec ~1.12.16');
+      expect(logSpy).toHaveBeenCalledWith(
+        'go-version-file-behavior: latest-patch implies check-latest'
+      );
+      expect(logSpy).toHaveBeenCalledWith(
+        'Attempting to resolve the latest version from the manifest...'
+      );
+      expect(logSpy).toHaveBeenCalledWith(
+        `Acquiring 1.12.17 from ${expectedUrl}`
+      );
+    });
+
+    it('warns and falls back when the manifest cannot be resolved', async () => {
+      os.platform = 'linux';
+      os.arch = 'x64';
+
+      inputs['go-version-file'] = 'go.mod';
+      inputs['go-version-file-behavior'] = 'latest-patch';
+      inputs['token'] = 'faketoken';
+      existsSpy.mockImplementation(() => true);
+      readFileSpy.mockImplementation(() => Buffer.from(buildGoMod('1.12.16')));
+
+      getManifestSpy.mockImplementation(() => {
+        throw new Error('Unable to download manifest');
+      });
+      (httpmGetJsonSpy as jest.Mock<any>).mockRejectedValue(
+        new Error('Unable to download manifest from raw URL')
+      );
+
+      // ... and not in the local cache, so the dist fallback downloads
+      findSpy.mockImplementation(() => '');
+      dlSpy.mockImplementation(async () => '/some/temp/path');
+      const toolPath = path.normalize('/cache/go/1.12.17/x64');
+      extractTarSpy.mockImplementation(async () => '/some/other/temp/path');
+      cacheSpy.mockImplementation(async () => toolPath);
+
+      await main.run();
+
+      expect(cnSpy).toHaveBeenCalledWith(
+        `::warning::go-version-file-behavior: latest-patch could not be honored: unable to resolve ~1.12.16 from the versions manifest. Falling back to the version spec, which may resolve to an older patch release from the runner's tool cache.${osm.EOL}`
+      );
+      expect(dlSpy).toHaveBeenCalled();
+    });
+
+    it('leaves a bare minor version unchanged with latest-patch', async () => {
+      inputs['go-version-file'] = 'go.mod';
+      inputs['go-version-file-behavior'] = 'latest-patch';
+      existsSpy.mockImplementation(() => true);
+      readFileSpy.mockImplementation(() => Buffer.from(buildGoMod('1.14')));
+
+      await main.run();
+
+      expect(logSpy).toHaveBeenCalledWith(
+        'Using version 1.14 as written (latest-patch only widens exact major.minor.patch versions)'
+      );
+      expect(logSpy).toHaveBeenCalledWith('Setup go version spec 1.14');
+    });
+
+    it('does not widen an explicit toolchain directive pin', async () => {
+      inputs['go-version-file'] = 'go.mod';
+      inputs['go-version-file-behavior'] = 'latest-patch';
+      existsSpy.mockImplementation(() => true);
+      readFileSpy.mockImplementation(() =>
+        Buffer.from(`module example.com/mymodule
+
+go 1.21
+
+toolchain go1.22.3
+`)
+      );
+
+      await main.run();
+
+      expect(logSpy).toHaveBeenCalledWith(
+        'Using toolchain directive version 1.22.3 as written (latest-patch does not widen an explicit toolchain pin)'
+      );
+      expect(logSpy).toHaveBeenCalledWith('Setup go version spec 1.22.3');
+    });
+
+    it('fails when combined with a custom download base URL', async () => {
+      inputs['go-version-file'] = 'go.mod';
+      inputs['go-version-file-behavior'] = 'latest-patch';
+      inputs['go-download-base-url'] = 'https://internal.example.com/go';
+      existsSpy.mockImplementation(() => true);
+      readFileSpy.mockImplementation(() => Buffer.from(buildGoMod('1.22.0')));
+
+      await main.run();
+
+      expect(cnSpy).toHaveBeenCalledWith(
+        `::error::go-version-file-behavior: 'latest-patch' is not supported with a custom download base URL because version ranges cannot be resolved against it. Use the default 'exact' behavior.${osm.EOL}`
+      );
+    });
+
+    it('uses the exact version by default', async () => {
+      inputs['go-version-file'] = 'go.mod';
+      existsSpy.mockImplementation(() => true);
+      readFileSpy.mockImplementation(() => Buffer.from(buildGoMod('1.12.16')));
+
+      await main.run();
+
+      expect(logSpy).toHaveBeenCalledWith('Setup go version spec 1.12.16');
+    });
+
+    it('does not apply to the go-version input', async () => {
+      inputs['go-version'] = '1.12.16';
+      inputs['go-version-file-behavior'] = 'latest-patch';
+
+      await main.run();
+
+      expect(logSpy).toHaveBeenCalledWith('Setup go version spec 1.12.16');
+    });
+
+    it('fails on an unsupported value', async () => {
+      inputs['go-version-file'] = 'go.mod';
+      inputs['go-version-file-behavior'] = 'newest';
+      existsSpy.mockImplementation(() => true);
+      readFileSpy.mockImplementation(() => Buffer.from(buildGoMod('1.12.16')));
+
+      await main.run();
+
+      expect(cnSpy).toHaveBeenCalledWith(
+        `::error::Invalid go-version-file-behavior: 'newest'. Supported values: 'exact', 'latest-patch'${osm.EOL}`
+      );
+    });
+
+    it('fails on an unsupported value even when go-version is used', async () => {
+      inputs['go-version'] = '1.12.16';
+      inputs['go-version-file-behavior'] = 'newest';
+
+      await main.run();
+
+      expect(cnSpy).toHaveBeenCalledWith(
+        `::error::Invalid go-version-file-behavior: 'newest'. Supported values: 'exact', 'latest-patch'${osm.EOL}`
+      );
+    });
+
+    it.each([
+      ['1.22.0', '~1.22.0'],
+      ['v1.22.0', '~1.22.0'],
+      ['1.22', '1.22'],
+      ['1.21rc2', '1.21rc2'],
+      ['1.22.x', '1.22.x'],
+      ['>=1.22.0', '>=1.22.0']
+    ])('latestPatchSpec(%s) == %s', (version, expected) => {
+      expect(im.latestPatchSpec(version)).toBe(expected);
+    });
+  });
+
   describe('go-version-file-toolchain', () => {
     const goVersions = ['1.22.0', '1.21rc2', '1.18'];
     const placeholderVersion = '1.19';

action.yml

@@ -6,6 +6,9 @@ inputs:
     description: 'The Go version to download (if necessary) and use. Supports semver spec and ranges. Be sure to enclose this option in single quotation marks.'
   go-version-file:
     description: 'Path to the go.mod, go.work, .go-version, or .tool-versions file.'
+  go-version-file-behavior:
+    description: 'How to interpret an exact version read from go-version-file. Use "latest-patch" to resolve the newest available patch release of the same minor version (e.g. "1.22.0" in go.mod resolves to the newest 1.22.x); this implies check-latest and is not supported with go-download-base-url. Defaults to "exact", which uses the version as written.'
+    default: exact
   check-latest:
     description: 'Set this option to true if you want the action to always check for the latest available version that satisfies the version spec'
     default: false

dist/setup/index.js

@@ -43462,7 +43462,7 @@ const GOLANG_DOWNLOAD_URL = 'https://go.dev/dl/?mode=json&include=all';
 // For these URLs we skip the getInfoFromDist() call entirely and construct
 // the download URL directly, avoiding a guaranteed-404 HTTP request.
 const NO_VERSION_LISTING_BASE_URLS = ['https://aka.ms/golang/release/latest'];
-async function getGo(versionSpec, checkLatest, auth, arch = external_os_default().arch(), goDownloadBaseUrl) {
+async function getGo(versionSpec, checkLatest, auth, arch = external_os_default().arch(), goDownloadBaseUrl, latestPatchApplied = false) {
     let manifest;
     const osPlat = external_os_default().platform();
     const customBaseUrl = goDownloadBaseUrl?.replace(/\/+$/, '');
@@ -43493,6 +43493,11 @@ async function getGo(versionSpec, checkLatest, auth, arch = external_os_default(
                 versionSpec = resolvedVersion;
                 core_info(`Resolved as '${versionSpec}'`);
             }
+            else if (latestPatchApplied) {
+                // latest-patch depends on the manifest to see patches newer than
+                // the runner's tool cache, so a silent info line is not enough here
+                warning(`go-version-file-behavior: latest-patch could not be honored: unable to resolve ${versionSpec} from the versions manifest. Falling back to the version spec, which may resolve to an older patch release from the runner's tool cache.`);
+            }
             else {
                 core_info(`Failed to resolve version ${versionSpec} from manifest`);
             }
@@ -43865,18 +43870,37 @@ function parseGoVersionFile(versionFilePath) {
             // toolchain directive: https://go.dev/ref/mod#go-mod-file-toolchain
             const matchToolchain = contents.match(/^toolchain go(1\.\d+(?:\.\d+|rc\d+)?)/m);
             if (matchToolchain) {
-                return matchToolchain[1];
+                return { version: matchToolchain[1], fromToolchainDirective: true };
             }
         }
         // go directive: https://go.dev/ref/mod#go-mod-file-go
         const matchGo = contents.match(/^go (\d+(\.\d+)*)/m);
-        return matchGo ? matchGo[1] : '';
+        return {
+            version: matchGo ? matchGo[1] : '',
+            fromToolchainDirective: false
+        };
     }
     else if (external_path_.basename(versionFilePath) === '.tool-versions') {
         const match = contents.match(/^golang\s+([^\n#]+)/m);
-        return match ? match[1].trim() : '';
+        return {
+            version: match ? match[1].trim() : '',
+            fromToolchainDirective: false
+        };
     }
-    return contents.trim();
+    return { version: contents.trim(), fromToolchainDirective: false };
+}
+// Widen an exact version from a version file into a semver range matching
+// the newest patch release of the same minor (go-version-file-behavior:
+// latest-patch). Only exact major.minor.patch versions are widened,
+// optionally with a leading 'v' as found in some .go-version files: bare
+// minors like '1.22' already resolve to the newest patch, and prereleases
+// like '1.21rc2' have no patch series to float within.
+function latestPatchSpec(version) {
+    const match = version.match(/^v?(\d+\.\d+\.\d+)$/);
+    if (!match) {
+        return version;
+    }
+    return `~${match[1]}`;
 }
 async function resolveStableVersionDist(versionSpec, arch) {
     const archFilter = getArch(arch);
@@ -100573,7 +100597,7 @@ async function run() {
         // versionSpec is optional.  If supplied, install / use from the tool cache
         // If not supplied then problem matchers will still be setup.  Useful for self-hosted.
         //
-        const versionSpec = resolveVersionInput();
+        const { version: versionSpec, latestPatchApplied } = resolveVersionInput();
         setGoToolchain();
         const cache = getBooleanInput('cache');
         core_info(`Setup go version spec ${versionSpec}`);
@@ -100584,14 +100608,20 @@ async function run() {
         if (versionSpec) {
             const token = getInput('token');
             const auth = !token ? undefined : `token ${token}`;
-            const checkLatest = getBooleanInput('check-latest');
+            let checkLatest = getBooleanInput('check-latest');
+            if (latestPatchApplied && !checkLatest) {
+                // the runner's tool cache may only hold a stale patch release; the
+                // newest one has to come from the versions manifest
+                core_info('go-version-file-behavior: latest-patch implies check-latest');
+                checkLatest = true;
+            }
             const goDownloadBaseUrl = getInput('go-download-base-url') ||
                 process.env['GO_DOWNLOAD_BASE_URL'] ||
                 undefined;
             if (goDownloadBaseUrl) {
                 core_info(`Using custom Go download base URL: ${goDownloadBaseUrl}`);
             }
-            const installDir = await getGo(versionSpec, checkLatest, auth, arch, goDownloadBaseUrl);
+            const installDir = await getGo(versionSpec, checkLatest, auth, arch, goDownloadBaseUrl, latestPatchApplied);
             const installDirVersion = external_path_default().basename(external_path_default().dirname(installDir));
             addPath(external_path_default().join(installDir, 'bin'));
             core_info('Added go to the path');
@@ -100672,19 +100702,43 @@ function parseGoVersion(versionString) {
 function resolveVersionInput() {
     let version = getInput('go-version');
     const versionFilePath = getInput('go-version-file');
+    const behavior = getInput('go-version-file-behavior') || 'exact';
+    if (behavior !== 'exact' && behavior !== 'latest-patch') {
+        throw new Error(`Invalid go-version-file-behavior: '${behavior}'. Supported values: 'exact', 'latest-patch'`);
+    }
     if (version && versionFilePath) {
         warning('Both go-version and go-version-file inputs are specified, only go-version will be used');
     }
     if (version) {
-        return version;
+        return { version, latestPatchApplied: false };
     }
     if (versionFilePath) {
         if (!external_fs_default().existsSync(versionFilePath)) {
             throw new Error(`The specified go version file at: ${versionFilePath} does not exist`);
         }
-        version = parseGoVersionFile(versionFilePath);
+        const versionFile = parseGoVersionFile(versionFilePath);
+        version = versionFile.version;
+        if (behavior === 'latest-patch' && version) {
+            if (versionFile.fromToolchainDirective) {
+                core_info(`Using toolchain directive version ${version} as written (latest-patch does not widen an explicit toolchain pin)`);
+            }
+            else {
+                const spec = latestPatchSpec(version);
+                if (spec === version) {
+                    core_info(`Using version ${version} as written (latest-patch only widens exact major.minor.patch versions)`);
+                }
+                else {
+                    if (getInput('go-download-base-url') ||
+                        process.env['GO_DOWNLOAD_BASE_URL']) {
+                        throw new Error(`go-version-file-behavior: 'latest-patch' is not supported with a custom download base URL because version ranges cannot be resolved against it. Use the default 'exact' behavior.`);
+                    }
+                    core_info(`Using latest patch release satisfying ${spec} (version file specifies ${version})`);
+                    return { version: spec, latestPatchApplied: true };
+                }
+            }
+        }
     }
-    return version;
+    return { version, latestPatchApplied: false };
 }
 function setGoToolchain() {
     // docs: https://go.dev/doc/toolchain

docs/advanced-usage.md

@@ -3,6 +3,7 @@
   - [Specifying a go version](advanced-usage.md#specifying-a-go-version)
   - [Matrix testing](advanced-usage.md#matrix-testing)
 - [Using the go-version-file input](advanced-usage.md#using-the-go-version-file-input)
+  - [Using the latest patch release](advanced-usage.md#using-the-latest-patch-release)
 - [Check latest version](advanced-usage.md#check-latest-version)
 - [Caching](advanced-usage.md#caching)
   - [Caching in monorepos](advanced-usage.md#caching-in-monorepos)
@@ -212,6 +213,37 @@ steps:
   - run: go version
 ```
 
+### Using the latest patch release
+
+By default, an exact version read from the version file is used as written: a `go 1.22.0` directive installs exactly Go 1.22.0, even if newer 1.22.x patch releases with security fixes are available.
+
+Set `go-version-file-behavior` to `latest-patch` to instead resolve the newest available patch release of the same minor version that is at least the version in the file (e.g., `go 1.22.0` resolves to the newest 1.22.x):
+
+```yaml
+steps:
+  - uses: actions/checkout@v7
+  - uses: actions/setup-go@v7
+    with:
+      go-version-file: 'go.mod'
+      go-version-file-behavior: 'latest-patch'
+  - run: go version
+```
+
+Because the newest patch release is often not yet present in the runner's tool cache, `latest-patch` implies `check-latest`: the newest matching patch is resolved from the versions manifest rather than from whatever the cache happens to hold.
+
+Two operational effects to be aware of:
+
+- The dependency cache key includes the installed Go version, so with `cache: true` each new Go patch release changes the key: the first run after a patch release rebuilds the module and build caches from scratch.
+- If the versions manifest cannot be reached (for example on GitHub Enterprise Server or other runners without github.com access), the action emits a warning and falls back to resolving the version range locally, which may install an older patch release from the runner's tool cache.
+
+Some versions are always used as written and are not affected by `latest-patch`:
+
+- Versions without a patch component (e.g., `go 1.22`), which already resolve to the latest available patch release.
+- Prerelease versions (e.g., `go1.22rc1`), which have no patch series to float within.
+- An exact version pinned by a go.mod or go.work `toolchain` directive (e.g., `toolchain go1.22.3`): the pin is deliberate and is never widened.
+
+`latest-patch` is not supported together with `go-download-base-url`, which requires an exact version.
+
 ## Check latest version
 
 The `check-latest` flag defaults to `false`. Use the default or set `check-latest` to `false` if you prefer stability

src/installer.ts

@@ -54,7 +54,8 @@ export async function getGo(
   checkLatest: boolean,
   auth: string | undefined,
   arch: Architecture = os.arch() as Architecture,
-  goDownloadBaseUrl?: string
+  goDownloadBaseUrl?: string,
+  latestPatchApplied = false
 ) {
   let manifest: tc.IToolRelease[] | undefined;
   const osPlat: string = os.platform();
@@ -111,6 +112,12 @@ export async function getGo(
       if (resolvedVersion) {
         versionSpec = resolvedVersion;
         core.info(`Resolved as '${versionSpec}'`);
+      } else if (latestPatchApplied) {
+        // latest-patch depends on the manifest to see patches newer than
+        // the runner's tool cache, so a silent info line is not enough here
+        core.warning(
+          `go-version-file-behavior: latest-patch could not be honored: unable to resolve ${versionSpec} from the versions manifest. Falling back to the version spec, which may resolve to an older patch release from the runner's tool cache.`
+        );
       } else {
         core.info(`Failed to resolve version ${versionSpec} from manifest`);
       }
@@ -642,7 +649,16 @@ export function makeSemver(version: string): string {
   return fullVersion;
 }
 
-export function parseGoVersionFile(versionFilePath: string): string {
+export interface GoVersionFileResult {
+  version: string;
+  // true when the version came from a go.mod/go.work toolchain directive,
+  // an explicit pin that must be respected as written
+  fromToolchainDirective: boolean;
+}
+
+export function parseGoVersionFile(
+  versionFilePath: string
+): GoVersionFileResult {
   const contents = fs.readFileSync(versionFilePath).toString();
 
   if (
@@ -657,19 +673,39 @@ export function parseGoVersionFile(versionFilePath: string): string {
         /^toolchain go(1\.\d+(?:\.\d+|rc\d+)?)/m
       );
       if (matchToolchain) {
-        return matchToolchain[1];
+        return {version: matchToolchain[1], fromToolchainDirective: true};
       }
     }
 
     // go directive: https://go.dev/ref/mod#go-mod-file-go
     const matchGo = contents.match(/^go (\d+(\.\d+)*)/m);
-    return matchGo ? matchGo[1] : '';
+    return {
+      version: matchGo ? matchGo[1] : '',
+      fromToolchainDirective: false
+    };
   } else if (path.basename(versionFilePath) === '.tool-versions') {
     const match = contents.match(/^golang\s+([^\n#]+)/m);
-    return match ? match[1].trim() : '';
+    return {
+      version: match ? match[1].trim() : '',
+      fromToolchainDirective: false
+    };
   }
 
-  return contents.trim();
+  return {version: contents.trim(), fromToolchainDirective: false};
+}
+
+// Widen an exact version from a version file into a semver range matching
+// the newest patch release of the same minor (go-version-file-behavior:
+// latest-patch). Only exact major.minor.patch versions are widened,
+// optionally with a leading 'v' as found in some .go-version files: bare
+// minors like '1.22' already resolve to the newest patch, and prereleases
+// like '1.21rc2' have no patch series to float within.
+export function latestPatchSpec(version: string): string {
+  const match = version.match(/^v?(\d+\.\d+\.\d+)$/);
+  if (!match) {
+    return version;
+  }
+  return `~${match[1]}`;
 }
 
 async function resolveStableVersionDist(

src/main.ts

@@ -17,7 +17,7 @@ export async function run() {
     // versionSpec is optional.  If supplied, install / use from the tool cache
     // If not supplied then problem matchers will still be setup.  Useful for self-hosted.
     //
-    const versionSpec = resolveVersionInput();
+    const {version: versionSpec, latestPatchApplied} = resolveVersionInput();
     setGoToolchain();
 
     const cache = core.getBooleanInput('cache');
@@ -33,7 +33,15 @@ export async function run() {
       const token = core.getInput('token');
       const auth = !token ? undefined : `token ${token}`;
 
-      const checkLatest = core.getBooleanInput('check-latest');
+      let checkLatest = core.getBooleanInput('check-latest');
+      if (latestPatchApplied && !checkLatest) {
+        // the runner's tool cache may only hold a stale patch release; the
+        // newest one has to come from the versions manifest
+        core.info(
+          'go-version-file-behavior: latest-patch implies check-latest'
+        );
+        checkLatest = true;
+      }
 
       const goDownloadBaseUrl =
         core.getInput('go-download-base-url') ||
@@ -49,7 +57,8 @@ export async function run() {
         checkLatest,
         auth,
         arch,
-        goDownloadBaseUrl
+        goDownloadBaseUrl,
+        latestPatchApplied
       );
 
       const installDirVersion = path.basename(path.dirname(installDir));
@@ -152,10 +161,25 @@ export function parseGoVersion(versionString: string): string {
   return versionString.split(' ')[2].slice('go'.length);
 }
 
-function resolveVersionInput(): string {
+interface ResolvedVersionInput {
+  version: string;
+  // true when latest-patch widened the version into a range; the newest
+  // matching patch must then be resolved from the versions manifest, not
+  // just the runner's local tool cache
+  latestPatchApplied: boolean;
+}
+
+function resolveVersionInput(): ResolvedVersionInput {
   let version = core.getInput('go-version');
   const versionFilePath = core.getInput('go-version-file');
 
+  const behavior = core.getInput('go-version-file-behavior') || 'exact';
+  if (behavior !== 'exact' && behavior !== 'latest-patch') {
+    throw new Error(
+      `Invalid go-version-file-behavior: '${behavior}'. Supported values: 'exact', 'latest-patch'`
+    );
+  }
+
   if (version && versionFilePath) {
     core.warning(
       'Both go-version and go-version-file inputs are specified, only go-version will be used'
@@ -163,7 +187,7 @@ function resolveVersionInput(): string {
   }
 
   if (version) {
-    return version;
+    return {version, latestPatchApplied: false};
   }
 
   if (versionFilePath) {
@@ -172,10 +196,39 @@ function resolveVersionInput(): string {
         `The specified go version file at: ${versionFilePath} does not exist`
       );
     }
-    version = installer.parseGoVersionFile(versionFilePath);
+    const versionFile = installer.parseGoVersionFile(versionFilePath);
+    version = versionFile.version;
+
+    if (behavior === 'latest-patch' && version) {
+      if (versionFile.fromToolchainDirective) {
+        core.info(
+          `Using toolchain directive version ${version} as written (latest-patch does not widen an explicit toolchain pin)`
+        );
+      } else {
+        const spec = installer.latestPatchSpec(version);
+        if (spec === version) {
+          core.info(
+            `Using version ${version} as written (latest-patch only widens exact major.minor.patch versions)`
+          );
+        } else {
+          if (
+            core.getInput('go-download-base-url') ||
+            process.env['GO_DOWNLOAD_BASE_URL']
+          ) {
+            throw new Error(
+              `go-version-file-behavior: 'latest-patch' is not supported with a custom download base URL because version ranges cannot be resolved against it. Use the default 'exact' behavior.`
+            );
+          }
+          core.info(
+            `Using latest patch release satisfying ${spec} (version file specifies ${version})`
+          );
+          return {version: spec, latestPatchApplied: true};
+        }
+      }
+    }
   }
 
-  return version;
+  return {version, latestPatchApplied: false};
 }
 
 function setGoToolchain() {