[batch] Option to clean files before generation

bin/generate-samples.sh

@@ -11,6 +11,7 @@ if [ ! -f "$executable" ]; then
 fi
 
 export JAVA_OPTS="${JAVA_OPTS} -ea -server -Duser.timezone=UTC"
+export BATCH_OPTS="${BATCH_OPTS:-}"
 
 files=()
 args=()
@@ -61,6 +62,6 @@ else
 
     # shellcheck disable=SC2086
     # shellcheck disable=SC2068
-    java ${JAVA_OPTS} -jar "$executable" batch --includes-base-dir "${root}" --fail-fast  -- ${files[@]}
+    java ${JAVA_OPTS} -jar "$executable" batch ${BATCH_OPTS} --includes-base-dir "${root}" --fail-fast  -- ${files[@]}
 fi
 

modules/openapi-generator-cli/src/main/java/org/openapitools/codegen/cmd/GenerateBatch.java

@@ -34,6 +34,7 @@
 import io.airlift.airline.Arguments;
 import io.airlift.airline.Command;
 import io.airlift.airline.Option;
+import org.apache.commons.io.FileUtils;
 import org.apache.commons.lang3.StringUtils;
 import org.openapitools.codegen.ClientOptInput;
 import org.openapitools.codegen.CodegenConfig;
@@ -46,6 +47,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
@@ -77,6 +79,9 @@ public class GenerateBatch extends OpenApiGeneratorCommand {
     @Option(name = {"--fail-fast"}, description = "fail fast on any errors")
     private Boolean failFast;
 
+    @Option(name = {"--clean"}, description = "clean output of previously written files before generation")
+    private Boolean clean;
+
     @Option(name = {"--timeout"}, description = "execution timeout (minutes)")
     private Integer timeout;
 
@@ -149,7 +154,10 @@ public void execute() {
         ExecutorService executor = Executors.newFixedThreadPool(numThreads);
 
         // Execute each configurator on a separate pooled thread.
-        configurators.forEach(configurator -> executor.execute(new GenerationRunner(configurator, rootDir, Boolean.TRUE.equals(failFast))));
+        configurators.forEach(configurator -> {
+            GenerationRunner runner = new GenerationRunner(configurator, rootDir, Boolean.TRUE.equals(failFast), Boolean.TRUE.equals(clean));
+            executor.execute(runner);
+        });
 
         executor.shutdown();
 
@@ -178,11 +186,13 @@ private static class GenerationRunner implements Runnable {
         private final CodegenConfigurator configurator;
         private final Path rootDir;
         private final boolean exitOnError;
+        private final boolean clean;
 
-        private GenerationRunner(CodegenConfigurator configurator, Path rootDir, boolean failFast) {
+        private GenerationRunner(CodegenConfigurator configurator, Path rootDir, boolean failFast, boolean clean) {
             this.configurator = configurator;
             this.rootDir = rootDir;
             this.exitOnError = failFast;
+            this.clean = clean;
         }
 
         /**
@@ -198,7 +208,7 @@ private GenerationRunner(CodegenConfigurator configurator, Path rootDir, boolean
          */
         @Override
         public void run() {
-            String name = "";
+            String name = null;
             try {
                 GlobalSettings.reset();
 
@@ -210,6 +220,10 @@ public void run() {
                 Path updated = rootDir.resolve(target);
                 config.setOutputDir(updated.toString());
 
+                if (this.clean) {
+                    cleanPreviousFiles(name, updated);
+                }
+
                 System.out.printf(Locale.ROOT, "[%s] Generating %s (outputs to %s)…%n", Thread.currentThread().getName(), name, updated.toString());
 
                 DefaultGenerator defaultGenerator = new DefaultGenerator();
@@ -234,6 +248,28 @@ public void run() {
                 GlobalSettings.reset();
             }
         }
+
+        private void cleanPreviousFiles(final String name, Path outDir) throws IOException {
+            System.out.printf(Locale.ROOT, "[%s] Cleaning previous contents for %s in %s…%n", Thread.currentThread().getName(), name, outDir.toString());
+            Path filesMeta = Paths.get(outDir.toAbsolutePath().toString(), ".openapi-generator", "FILES");
+            if (filesMeta.toFile().exists()) {
+                FileUtils.readLines(filesMeta.toFile(), StandardCharsets.UTF_8).forEach(relativePath -> {
+                    if (!StringUtils.startsWith(relativePath, ".")) {
+                        Path file = outDir.resolve(relativePath).toAbsolutePath();
+                        // hack: disallow directory traversal outside of output directory. we don't want to delete wrong files.
+                        if (file.toString().startsWith(outDir.toAbsolutePath().toString())) {
+                            try {
+                                Files.delete(file);
+                            } catch (Throwable e) {
+                                System.out.printf(Locale.ROOT, "[%s] Generator %s failed to clean file %s…%n", Thread.currentThread().getName(), name, file);
+                            }
+                        }
+                    } else {
+                        System.out.printf(Locale.ROOT, "[%s] Generator %s skip cleaning special filename %s…%n", Thread.currentThread().getName(), name, relativePath);
+                    }
+                });
+            }
+        }
     }
 
     static SimpleModule getCustomDeserializationModel(final File includesDir) {