Invalidate Importlib's Module Cache on Writes to FS (#996)

* Add runtime.invalidate_module_path_cache() to clear importlib's cache of modules

* Clear cache after [[fetch]], after plugin files download, after plugins setup, and prior to py-script tag execution.

pyscriptjs/src/main.ts

@@ -179,6 +179,8 @@ export class PyScriptApp {
         // lifecycle (6.5)
         this.plugins.afterSetup(runtime);
 
+        //Refresh module cache in case plugins have modified the filesystem
+        runtime.invalidate_module_path_cache()
         this.logStatus('Executing <py-script> tags...');
         this.executeScripts(runtime);
 
@@ -205,6 +207,8 @@ export class PyScriptApp {
 
         // Save and load pyscript.py from FS
         runtime.interpreter.FS.writeFile('pyscript.py', pyscript, { encoding: 'utf8' });
+        //Refresh the module cache so Python consistently finds pyscript module
+        runtime.invalidate_module_path_cache()
 
         // inject `define_custom_element` it into the PyScript module scope
         const pyscript_module = runtime.interpreter.pyimport('pyscript');
@@ -227,6 +231,8 @@ from pyscript import micropip, Element, console, document`);
         await runtime.installPackage(this.config.packages);
         await this.fetchPaths(runtime);
 
+        //This may be unnecessary - only useful if plugins try to import files fetch'd in fetchPaths()
+        runtime.invalidate_module_path_cache()
         // Finally load plugins
         await this.fetchPythonPlugins(runtime);
     }
@@ -273,6 +279,10 @@ from pyscript import micropip, Element, console, document`);
                 // TODO: Would be probably be better to store plugins somewhere like /plugins/python/ or similar
                 const destPath = `./${filename}`;
                 await runtime.loadFromFile(destPath, singleFile);
+
+                //refresh module cache before trying to import module files into runtime
+                runtime.invalidate_module_path_cache()
+
                 const modulename = singleFile.replace(/^.*[\\/]/, '').replace('.py', '');
 
                 console.log(`importing ${modulename}`);

pyscriptjs/src/pyodide.ts

@@ -118,4 +118,9 @@ export class PyodideRuntime extends Runtime {
         this.interpreter.FS.write(stream, data, 0, data.length, 0);
         this.interpreter.FS.close(stream);
     }
+
+    invalidate_module_path_cache(): void {
+        const importlib = this.interpreter.pyimport("importlib")
+        importlib.invalidate_caches()
+    }
 }

pyscriptjs/src/runtime.ts

@@ -100,4 +100,10 @@ export abstract class Runtime extends Object {
      * underlying interpreter.
      * */
     abstract loadFromFile(path: string, fetch_path: string): Promise<void>;
+
+    /**
+     * delegates clearing importlib's module path
+     * caches to the underlying interpreter
+     */
+    abstract invalidate_module_path_cache(): void;
 }

pyscriptjs/tests/unit/fakeruntime.ts

@@ -36,4 +36,8 @@ export class FakeRuntime extends Runtime {
     async loadFromFile(path: string, fetch_path: string) {
         throw new Error("not implemented");
     }
+
+    invalidate_module_path_cache(): void {
+        throw new Error("not implemented");
+    }
 }