modrinth: handle empty projects list as removing all

src/main/java/me/itzg/helpers/modrinth/ModrinthCommand.java

@@ -111,23 +111,38 @@ public enum DownloadDependencies {
     public Integer call() throws Exception {
         Files.createDirectories(outputDirectory);
 
-        final ModrinthManifest prevManifest = loadManifest();
+        // Unlike @Parameters, the argument of @Option could be a list with a single empty string
+        // when --projects="". So, trim away any blanks.
+        final List<String> trimmedProjects = projects == null ? Collections.emptyList() :
+            projects.stream()
+                .filter(s -> !s.trim().isEmpty())
+                .collect(Collectors.toList());
 
-        final List<Path> outputFiles = processProjects(projects);
+        final List<Path> outputFiles = processProjects(trimmedProjects);
 
         final ModrinthManifest newManifest = ModrinthManifest.builder()
             .files(Manifests.relativizeAll(outputDirectory, outputFiles))
             .projects(projects)
             .build();
 
+        final ModrinthManifest prevManifest = loadManifest();
         Manifests.cleanup(outputDirectory, prevManifest, newManifest, log);
 
-        Manifests.save(outputDirectory, ModrinthManifest.ID, newManifest);
+        if (!outputFiles.isEmpty()) {
+            Manifests.save(outputDirectory, ModrinthManifest.ID, newManifest);
+        }
+        else {
+            Manifests.remove(outputDirectory, ModrinthManifest.ID);
+        }
 
         return ExitCode.OK;
     }
 
     private List<Path> processProjects(List<String> projects) {
+        if (projects == null || projects.isEmpty()) {
+            return Collections.emptyList();
+        }
+
         try (ModrinthApiClient modrinthApiClient = new ModrinthApiClient(baseUrl, "modrinth", sharedFetchArgs.options())) {
             //noinspection DataFlowIssue since it thinks block() may return null
             return

src/test/java/me/itzg/helpers/modrinth/ModrinthCommandTest.java

@@ -3,8 +3,6 @@
 import static com.github.stefanbirkner.systemlambda.SystemLambda.tapSystemErrNormalized;
 import static com.github.tomakehurst.wiremock.client.WireMock.*;
 import static com.github.tomakehurst.wiremock.core.WireMockConfiguration.wireMockConfig;
-import static org.apache.commons.lang3.RandomStringUtils.randomAlphabetic;
-import static org.apache.commons.lang3.RandomStringUtils.randomAlphanumeric;
 import static org.assertj.core.api.Assertions.assertThat;
 
 import com.fasterxml.jackson.core.JsonProcessingException;
@@ -24,6 +22,7 @@
 import me.itzg.helpers.modrinth.ModrinthCommand.DownloadDependencies;
 import me.itzg.helpers.modrinth.model.Project;
 import me.itzg.helpers.modrinth.model.ProjectType;
+import org.apache.commons.lang3.RandomStringUtils;
 import org.assertj.core.api.AbstractPathAssert;
 import org.jetbrains.annotations.NotNull;
 import org.junit.jupiter.api.Test;
@@ -48,6 +47,8 @@ class ModrinthCommandTest {
         .configureStaticDsl(true)
         .build();
 
+    private final RandomStringUtils randomStringUtils = RandomStringUtils.insecure();
+
     @Test
     void commaNewlineDelimited(@TempDir Path tempDir) {
         setupStubs();
@@ -153,6 +154,15 @@ else if (downloadDependencies == DownloadDependencies.OPTIONAL) {
         }
     }
 
+    private String randomAlphanumeric(int n) {
+        return randomStringUtils.nextAlphanumeric(n);
+    }
+
+    @SuppressWarnings("SameParameterValue")
+    private String randomAlphabetic(int n) {
+        return randomStringUtils.nextAlphabetic(n);
+    }
+
     @Test
     void failsWhenNoDependenciesForModLoader(@TempDir Path tempDir) throws JsonProcessingException {
         final String projectId = randomAlphanumeric(6);
@@ -162,11 +172,11 @@ void failsWhenNoDependenciesForModLoader(@TempDir Path tempDir) throws JsonProce
 
         stubProjectBulkRequest(projectId, projectSlug);
 
-        stubVersionRequest(projectId, versionId, deps -> {
+        stubVersionRequest(projectId, versionId, deps ->
             deps.addObject()
-                .put("project_id", requiredDepProjectId)
-                .put("dependency_type", "required");
-        });
+            .put("project_id", requiredDepProjectId)
+            .put("dependency_type", "required")
+        );
         stubVersionRequestEmptyResponse(requiredDepProjectId, "paper");
         stubVersionRequestEmptyResponse(requiredDepProjectId, "spigot");
         stubGetProject(requiredDepProjectId, new Project().setProjectType(ProjectType.resourcepack));
@@ -277,7 +287,6 @@ void handlesDatapacksSpecificVersion(boolean absoluteWorldDir, @TempDir Path tem
 
         stubProjectBulkRequest(projectId, projectSlug);
 
-        final ArrayNode versionResp = objectMapper.createArrayNode();
         final ObjectNode versionNode = objectMapper.createObjectNode()
             .put("id", versionId)
             .put("project_id", projectId)
@@ -412,6 +421,51 @@ void usingListingFile(@TempDir Path tempDir) throws Exception {
         assertThat(tempDir.resolve("mods/cloth-config-8.3.103-fabric.jar")).exists();
     }
 
+    @Test
+    void removesAllWhenEmpty(@TempDir Path tempDir) {
+        setupStubs();
+
+        {
+            final int exitCode = new CommandLine(
+                new ModrinthCommand()
+            )
+                .execute(
+                    "--api-base-url", wm.getRuntimeInfo().getHttpBaseUrl(),
+                    "--output-directory", tempDir.toString(),
+                    "--game-version", "1.19.2",
+                    "--loader", "fabric",
+                    "--projects", "fabric-api,cloth-config"
+                );
+
+            assertThat(exitCode).isEqualTo(ExitCode.OK);
+
+            assertThat(tempDir.resolve("mods/fabric-api-0.76.1+1.19.2.jar")).exists();
+            assertThat(tempDir.resolve("mods/cloth-config-8.3.103-fabric.jar")).exists();
+        }
+
+        // now process an empty projects list to uninstall all
+        {
+            final int exitCode = new CommandLine(
+                new ModrinthCommand()
+            )
+                .execute(
+                    "--api-base-url", wm.getRuntimeInfo().getHttpBaseUrl(),
+                    "--output-directory", tempDir.toString(),
+                    "--game-version", "1.19.2",
+                    "--loader", "fabric",
+                    "--projects", ""
+                );
+
+            assertThat(exitCode).isEqualTo(ExitCode.OK);
+
+            // assert files now do NOT exist
+            assertThat(tempDir.resolve("mods/fabric-api-0.76.1+1.19.2.jar"))
+                .doesNotExist();
+            assertThat(tempDir.resolve("mods/cloth-config-8.3.103-fabric.jar"))
+                .doesNotExist();
+        }
+    }
+
     @NotNull
     private static RequestPatternBuilder projectVersionsRequest(String projectId) {
         return getRequestedFor(urlPathEqualTo("/v2/project/" + projectId + "/version"));