MCP cgen_run tool: correctly set last modification time

Author: stariy95

cayenne-mcp-server/src/main/java/org/apache/cayenne/mcp/tools/cgen/CgenRunTool.java

@@ -168,6 +168,18 @@ public CgenRunResult run(String projectPath, String dataMapName) {
         }
         CgenConfiguration cgenConfig = configList.getAll().getFirst();
 
+        // Set the DataMap file's mtime as the timestamp so fileNeedUpdate() can detect DataMap changes correctly.
+        if (dataMap.getConfigurationSource() != null) {
+            try {
+                Path dataMapFile = Path.of(dataMap.getConfigurationSource().getURL().toURI());
+                cgenConfig.setTimestamp(Files.getLastModifiedTime(dataMapFile).toMillis());
+            } catch (Exception e) {
+                // URI conversion failed (e.g. non-file: URL) or some problems with file mtime read,
+                // better to regen all, than silently fail.
+                cgenConfig.setForce(true);
+            }
+        }
+
         // Step 5 — destDir specified?
         Path destDir = cgenConfig.buildOutputPath();
         if (destDir == null) {

cayenne-mcp-server/src/test/java/org/apache/cayenne/mcp/tools/cgen/CgenRunIT.java

@@ -28,6 +28,7 @@
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.nio.file.attribute.FileTime;
 import java.util.List;
 
 import static org.junit.jupiter.api.Assertions.*;
@@ -117,6 +118,30 @@ public void subclassNotOverwrittenWhenMakePairsIsTrue() throws IOException {
         assertTrue(skipped >= 1, "At least one file (the existing subclass) should have been skipped");
     }
 
+    @Test
+    public void regeneratesAfterDataMapChange() throws IOException {
+        // First run — generates files
+        CgenRunResult first = tool.run(projectFile.toString(), "PersonMap");
+        assertEquals("generated", first.status());
+
+        // Bump the DataMap's mtime to be clearly newer than the generated files.
+        // Use setLastModifiedTime rather than a wall-clock sleep to avoid
+        // filesystem mtime granularity issues (Windows has 1-second resolution).
+        long maxGeneratedMtime = first.files().stream()
+                .mapToLong(e -> Path.of(e.path()).toFile().lastModified())
+                .max()
+                .orElseThrow();
+        Path dataMapFile = tempDir.resolve("PersonMap.map.xml");
+        Files.setLastModifiedTime(dataMapFile, FileTime.fromMillis(maxGeneratedMtime + 5_000L));
+
+        // Second run — must detect that the DataMap is newer than the generated files
+        // and regenerate the superclass(es).
+        CgenRunResult second = tool.run(projectFile.toString(), "PersonMap");
+        assertEquals("generated", second.status(),
+                "Expected regeneration after DataMap mtime was bumped past generated files");
+        assertTrue(second.summary().filesWritten() > 0);
+    }
+
     private Path writeFixture(String mapName, String pkg, Path destDir, boolean makePairs) throws IOException {
 
         // Project descriptor