feat(core): add a method to help getting a file extension

core/src/main/java/io/kestra/core/runners/RunContext.java

@@ -24,6 +24,8 @@
 import io.micronaut.inject.qualifiers.Qualifiers;
 import lombok.NoArgsConstructor;
 import org.apache.commons.io.FileUtils;
+import org.apache.commons.io.FilenameUtils;
+import org.apache.commons.lang3.StringUtils;
 
 import java.io.*;
 import java.net.URI;
@@ -480,6 +482,17 @@ public URI putTempFile(File file, String name) throws IOException {
         return this.putTempFile(file, this.storageOutputPrefix.toString(), name);
     }
 
+    /**
+     * Put the temporary file on storage and delete it after.
+     * This method is meant to be used by polling triggers, the name of the destination file is derived from the
+     * executionId and the trigger passed as parameters.
+     *
+     * @param file the temporary file to upload to storage
+     * @param executionId overwrite file name
+     * @param trigger the trigger
+     * @return the {@code StorageObject} created
+     * @throws IOException If the temporary file can't be read
+     */
     public URI putTempFile(File file, String executionId, AbstractTrigger trigger) throws IOException {
         return this.putTempFile(
             file,
@@ -680,6 +693,16 @@ public Path tempFile(byte[] content, String suffix) throws IOException {
         return tempFile;
     }
 
+    /**
+     * Get the file extension including the '.' to be used with the various methods that took a suffix.
+     * @param fileName the name of the file
+     * @return the file extension including the '.' or null
+     */
+    public String fileExtension(String fileName) {
+        String extension = FilenameUtils.getExtension(fileName);
+        return StringUtils.isEmpty(extension) ? null : "." + extension;
+    }
+
     public void cleanup() {
         try {
             this.cleanTemporaryDirectory();

core/src/test/java/io/kestra/core/runners/RunContextTest.java

@@ -178,4 +178,14 @@ void metricsIncrement() {
         assertThat(runContext.metrics().get(3).getValue(), is(Duration.ofSeconds(123)));
         assertThat(runContext.metrics().get(3).getTags().size(), is(1));
     }
+
+    @Test
+    void fileExtension() {
+        RunContext runContext = runContextFactory.of();
+
+        assertThat(runContext.fileExtension(null), nullValue());
+        assertThat(runContext.fileExtension(""), nullValue());
+        assertThat(runContext.fileExtension("/file/hello"), nullValue());
+        assertThat(runContext.fileExtension("/file/hello.txt"), is(".txt"));
+    }
 }