fabric: skip fabricmc API call when matching version installed

Author: itzg

src/main/java/me/itzg/helpers/fabric/FabricMetaClient.java

@@ -37,17 +37,21 @@ static boolean nonEmptyString(String loaderVersion) {
      * @param version can be latest, snapshot or specific
      */
     public Mono<String> resolveMinecraftVersion(@Nullable String version) {
+        if (!isLatest(version) && !isSnapshot(version)) {
+            return Mono.just(version);
+        }
+
         return sharedFetch.fetch(
                 uriBuilder.resolve("/v2/versions/game")
             )
             .toObjectList(VersionEntry.class)
             .assemble()
             .flatMap(versionEntries -> {
-                if (version == null || version.equalsIgnoreCase("latest")) {
+                if (isLatest(version)) {
                     return findFirst(versionEntries, VersionEntry::isStable)
                         .switchIfEmpty(Mono.error(() -> new GenericException("Unable to find any stable versions")));
                 }
-                else if (version.equalsIgnoreCase("snapshot")) {
+                else if (isSnapshot(version)) {
                     return findFirst(versionEntries, versionEntry -> !versionEntry.isStable())
                         .switchIfEmpty(Mono.error(() -> new GenericException("Unable to find any unstable versions")));
                 }
@@ -58,6 +62,14 @@ else if (version.equalsIgnoreCase("snapshot")) {
             });
     }
 
+    private static boolean isSnapshot(@Nullable String version) {
+        return version != null && version.equalsIgnoreCase("snapshot");
+    }
+
+    private static boolean isLatest(@Nullable String version) {
+        return version == null || version.equalsIgnoreCase("latest");
+    }
+
     public Mono<String> resolveLoaderVersion(String minecraftVersion, String loaderVersion) {
         if (nonEmptyString(loaderVersion)) {
             return Mono.just(loaderVersion);

src/test/java/me/itzg/helpers/fabric/FabricLauncherInstallerTest.java

@@ -201,6 +201,50 @@ void testUpgradeFromVersionToVersion(WireMockRuntimeInfo wmRuntimeInfo) {
             .doesNotExist();
     }
 
+    @Test
+    void testNoNetworkUsageWhenVersionMatches(WireMockRuntimeInfo wmRuntimeInfo) {
+        final WireMock wm = wmRuntimeInfo.getWireMock();
+        wm.loadMappingsFrom("src/test/resources/fabric");
+
+        final FabricLauncherInstaller installer = new FabricLauncherInstaller(
+            tempDir
+        );
+        installer.setFabricMetaBaseUrl(wmRuntimeInfo.getHttpBaseUrl());
+
+        installer.installUsingVersions(
+            "1.19.2", null, null
+        );
+
+        wm.verifyThat(
+            // since minecraft version is pinned
+            0,
+            getRequestedFor(urlEqualTo("/v2/versions/game")));
+        wm.verifyThat(
+            // to lookup installer version
+            1,
+            getRequestedFor(urlEqualTo("/v2/versions/installer")));
+
+        final Path expectedLauncher192 = tempDir.resolve("fabric-server-mc.1.19.2-loader.0.14.12-launcher.0.11.1.jar");
+        assertThat(expectedLauncher192)
+            .isNotEmptyFile()
+            .hasContent("fabric-server-mc.1.19.2-loader.0.14.12-launcher.0.11.1");
+
+        // Now try again with same
+
+        wm.resetRequests();
+
+        installer.installUsingVersions(
+            "1.19.2", "0.14.12", "0.11.1"
+        );
+
+        assertThat(expectedLauncher192)
+            .isNotEmptyFile()
+            .hasContent("fabric-server-mc.1.19.2-loader.0.14.12-launcher.0.11.1");
+
+        wm.verifyThat(0, getRequestedFor(urlEqualTo("/v2/versions/game")));
+        wm.verifyThat(0, getRequestedFor(urlEqualTo("/v2/versions/installer")));
+    }
+
     @Test
     @EnabledIfSystemProperty(named = "testEnableManualTests", matches = "true", disabledReason = "For manual recording")
     void forRecordingVersionDiscovery() {