Merge pull request #3783 from ebean-orm/feature/init-migrations-do-not-overwrite

db-migration: Change I__ init scripts to NOT overwrite (allow customisation)

ebean-ddl-generator/src/main/java/io/ebeaninternal/dbmigration/DefaultDbMigration.java

@@ -397,12 +397,21 @@ public class DefaultDbMigration implements DbMigration {
   }
 
   /**
-   * Write (or override) the "repeatable" migration script.
+   * Write the "repeatable" or "init" migration script.
+   * <p>
+   * Repeatable ({@code R__}) scripts are always (re)written from their source
+   * (typically {@code extra-ddl.xml} views), but an init ({@code I__}) script is
+   * only written when it does not already exist. Init scripts run once to
+   * bootstrap a database and can be hand-tuned after first generation.
    */
-  private void writeExtraDdl(File migrationDir, DdlScript script) throws IOException {
+  void writeExtraDdl(File migrationDir, DdlScript script) throws IOException {
     String fullName = repeatableMigrationName(script.isInit(), script.getName());
-    logger.log(DEBUG, "writing repeatable script {0}", fullName);
     File file = new File(migrationDir, fullName);
+    if (script.isInit() && file.exists()) {
+      logger.log(DEBUG, "skip existing init script {0}", fullName);
+      return;
+    }
+    logger.log(DEBUG, "writing repeatable script {0}", fullName);
     try (Writer writer = IOUtils.newWriter(file)) {
       writer.write(script.getValue());
       writer.flush();

ebean-ddl-generator/src/test/java/io/ebeaninternal/dbmigration/DefaultDbMigrationTest.java

@@ -1,7 +1,15 @@
 package io.ebeaninternal.dbmigration;
 
+import io.ebeaninternal.extraddl.model.DdlScript;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
 
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
@@ -30,4 +38,51 @@ class DefaultDbMigrationTest {
     migration.checkDropVersion("1.0", "1.0.0");
     migration.checkDropVersion("1.0", "1.1");
   }
+
+  @Test
+  void writeExtraDdl_initScript_notOverwrittenWhenExists(@TempDir Path dir) throws IOException {
+    File migrationDir = dir.toFile();
+
+    migration.writeExtraDdl(migrationDir, initScript("partition help", "ORIGINAL"));
+    File initFile = new File(migrationDir, "I__partition_help.sql");
+    assertThat(initFile).exists().content().isEqualTo("ORIGINAL");
+
+    // hand-tune the generated init script
+    Files.writeString(initFile.toPath(), "CUSTOMISED");
+
+    // regeneration must not clobber an existing init script
+    migration.writeExtraDdl(migrationDir, initScript("partition help", "ORIGINAL"));
+    assertThat(initFile).content().isEqualTo("CUSTOMISED");
+  }
+
+  @Test
+  void writeExtraDdl_repeatableScript_alwaysRewritten(@TempDir Path dir) throws IOException {
+    File migrationDir = dir.toFile();
+
+    migration.writeExtraDdl(migrationDir, repeatableScript("my view", "V1"));
+    File file = new File(migrationDir, "R__my_view.sql");
+    assertThat(file).exists().content().isEqualTo("V1");
+
+    Files.writeString(file.toPath(), "STALE");
+
+    // repeatable scripts are regenerated from their source every time
+    migration.writeExtraDdl(migrationDir, repeatableScript("my view", "V1"));
+    assertThat(file).content().isEqualTo("V1");
+  }
+
+  private static DdlScript initScript(String name, String value) {
+    return script(name, value, true);
+  }
+
+  private static DdlScript repeatableScript(String name, String value) {
+    return script(name, value, false);
+  }
+
+  private static DdlScript script(String name, String value, boolean init) {
+    DdlScript script = new DdlScript();
+    script.setName(name);
+    script.setValue(value);
+    script.setInit(init);
+    return script;
+  }
 }