René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"__file__ is not set correctly in subsequent script executions on the same thread","articleBody":"Given the following script:\r\n\r\n```java\r\nfinal String script = \"#@output String res\\n\" + \"import os\\n\" + \"res = os.path.dirname(os.path.abspath(__file__)) + __file__\\n\";\r\nfor (int i =0; i\u003c5; i++) {\r\n\tfinal ScriptModule m = scriptService.run(\"add\" + i + \".py\", script, true).get();\r\n\tfinal Object result = m.getInfo().getLanguage().decode(m.getOutput(\"res\"));\r\n\tSystem.out.println(result);\r\n}\r\n```\r\n\r\nthe `__file__` variable will either: a) be set appropriately if this is the first time the script was run on a particular thread, or b) be unset, causing the script to fail.\r\n\r\nThe [ScriptModule](https://github.com/scijava/scijava-common/blob/3f0e32f14aa7c6f64f206d79af14c47c6aac0249/src/main/java/org/scijava/script/ScriptModule.java#L146) passes the file name to the engine. In Jython, this file name gets picked up in [the PyScriptEngine](https://github.com/jython/jython/blob/8c3734d1f09d0e2de8843c3d8f22b469b83e6860/src/org/python/jsr223/PyScriptEngine.java#L85-L89). In the pathological case, this `__file__` value is lost [here](https://github.com/jython/jython/blob/8c3734d1f09d0e2de8843c3d8f22b469b83e6860/src/org/python/jsr223/PyScriptEngine.java#L39)\r\n\r\nThis does not seem to be a core problem with the interpreter, e.g. reuse of an existing interpreter within a thread produces appropriate output:\r\n```java\r\nScriptEngineManager mgr = new ScriptEngineManager();\r\nScriptEngine pyEngine = mgr.getEngineByName(\"jython\");\r\nfinal String script = \"print __file__\\n\";\r\nfor (int i=0; i\u003c5; i++) {\r\n\tpyEngine.put(ScriptEngine.FILENAME, \"hello\" + i +\".py\");\r\n\tpyEngine.eval(script);\r\n}\r\n```\r\n\r\nHowever, in our case, a new `ScriptEngine` instance (and `interpreter` instance) is created for each execution, whether it's within the same thread or not. If we modify the previous script to do the same, we can reproduce the error:\r\n\r\n```java\r\nScriptEngineManager mgr = new ScriptEngineManager();\r\nfinal String script = \"print __file__\\n\";\r\nfor (int i=0; i\u003c5; i++) {\r\n\tScriptEngine pyEngine = mgr.getEngineByName(\"jython\");\r\n\tpyEngine.put(ScriptEngine.FILENAME, \"hello\" + i +\".py\");\r\n\tpyEngine.eval(script);\r\n}\r\n```\r\n\r\nSo this is either a bug in jython, or a misuse of the script engine on our part.","author":{"url":"https://github.com/hinerm","@type":"Person","name":"hinerm"},"datePublished":"2024-05-02T17:48:56.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/13/scripting-jython/issues/13"}