refactor: split _get_java_post_build_commands (#837)

JavaPlugin provides _get_java_post_build_commands() that is
called from derived classes.

/bin/java link is broken for rockcraft projects.
Split _get_java_link_commands() into _get_java_link_commands()
and _get_jar_link_commands() to allow rockcraft plugins
override _get_java_link_commands().

Co-authored-by: Tiago Nobrega <[email protected]>

craft_parts/plugins/base.py

@@ -99,33 +99,39 @@ class JavaPlugin(Plugin):
     symlink creation.
     """
 
-    def _get_java_post_build_commands(self) -> list[str]:
-        """Get the bash commands to structure a Java build in the part's install dir.
-
-        :return: The returned list contains the bash commands to do the following:
-
-          - Create bin/ and jar/ directories in ${CRAFT_PART_INSTALL};
-          - Find the ``java`` executable (provided by whatever jre the part used) and
-            link it as ${CRAFT_PART_INSTALL}/bin/java;
-          - Hardlink the .jar files generated in ${CRAFT_PART_BUILD} to
-            ${CRAFT_PART_INSTALL}/jar.
-        """
+    def _get_java_link_commands(self) -> list[str]:
+        """Get the bash commands to provide /bin/java symlink."""
         # pylint: disable=line-too-long
-        link_java = [
+        return [
             '# Find the "java" executable and make a link to it in CRAFT_PART_INSTALL/bin/java',
             "mkdir -p ${CRAFT_PART_INSTALL}/bin",
             "java_bin=$(find ${CRAFT_PART_INSTALL} -name java -type f -executable)",
             "ln -s --relative $java_bin ${CRAFT_PART_INSTALL}/bin/java",
         ]
+        # pylint: enable=line-too-long
 
-        link_jars = [
+    def _get_jar_link_commands(self) -> list[str]:
+        """Get the bash commands to provide ${CRAFT_STAGE}/jars."""
+        # pylint: disable=line-too-long
+        return [
             "# Find all the generated jars and hardlink them inside CRAFT_PART_INSTALL/jar/",
             "mkdir -p ${CRAFT_PART_INSTALL}/jar",
             r'find ${CRAFT_PART_BUILD}/ -iname "*.jar" -exec ln {} ${CRAFT_PART_INSTALL}/jar \;',
         ]
         # pylint: enable=line-too-long
 
-        return link_java + link_jars
+    def _get_java_post_build_commands(self) -> list[str]:
+        """Get the bash commands to structure a Java build in the part's install dir.
+
+        :return: The returned list contains the bash commands to do the following:
+
+          - Create bin/ and jar/ directories in ${CRAFT_PART_INSTALL};
+          - Find the ``java`` executable (provided by whatever jre the part used) and
+            link it as ${CRAFT_PART_INSTALL}/bin/java;
+          - Hardlink the .jar files generated in ${CRAFT_PART_BUILD} to
+            ${CRAFT_PART_INSTALL}/jar.
+        """
+        return self._get_java_link_commands() + self._get_jar_link_commands()
 
 
 class BasePythonPlugin(Plugin):