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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Cannot build wasm demo. Build fails at wasm-bindgen","articleBody":"When building the WASM demo app, I'm getting this error\r\n\r\n```\r\n$ npm run dev\r\n...\r\ni ｢wds｣: Project is running at http://localhost:8080/\r\ni ｢wds｣: webpack output is served from /\r\ni ｢wds｣: Content not from webpack is served from C:\\Projects\\RustPython\\wasm\\demo\r\n[INFO]: Checking for the Wasm target...\r\n[INFO]: Compiling to Wasm...\r\nwarning: unused imports: `IntoPyResult`, `PyInt`\r\n    --\u003e vm\\src\\exceptions.rs:1028:47\r\n     |\r\n1028 |         builtins::{traceback::PyTracebackRef, PyInt, PyTupleRef, PyTypeRef},\r\n     |                                               ^^^^^\r\n1029 |         function::{FuncArgs, IntoPyResult},\r\n     |                              ^^^^^^^^^^^^\r\n     |\r\n     = note: `#[warn(unused_imports)]` on by default\r\n\r\nwarning: unused import: `std::ops::Deref`\r\n    --\u003e vm\\src\\exceptions.rs:1034:9\r\n     |\r\n1034 |     use std::ops::Deref;\r\n     |         ^^^^^^^^^^^^^^^\r\n\r\nwarning: unused import: `_io::io_open as open`\r\n  --\u003e vm\\src\\stdlib\\io.rs:13:16\r\n   |\r\n13 | pub(crate) use _io::io_open as open;\r\n   |                ^^^^^^^^^^^^^^^^^^^^\r\n\r\nwarning: `rustpython-vm` (lib) generated 3 warnings\r\n    Finished dev [unoptimized + debuginfo] target(s) in 2.68s\r\n[INFO]: License key is set in Cargo.toml but no LICENSE file(s) were found; Please add the LICENSE file(s) to your project directory\r\n[INFO]: Installing wasm-bindgen...\r\nerror: failed to parse input file as wasm\r\n\r\nCaused by:\r\n    0: failed to parse code section\r\n    1: locals exceed maximum (at offset 18929596)\r\nError: Running the wasm-bindgen CLI\r\nCaused by: failed to execute `wasm-bindgen`: exited with exit code: 1\r\n  full command: \"C:\\\\Users\\\\\u003cUSER\u003e\\\\AppData\\\\Local\\\\.wasm-pack\\\\wasm-bindgen-866ccfefff3842a2\\\\wasm-bindgen.exe\" \"C:\\Projects\\RustPython\\\\target\\\\wasm32-unknown-unknown\\\\debug\\\\rustpython_wasm.wasm\" \"--out-dir\" \"C:\\Projects\\RustPython\\\\wasm\\\\lib\\\\pkg\" \"--typescript\" \"--target\" \"bundler\" \"--out-name\" \"index\" \"--debug\"\r\n× ｢wdm｣: Hash: 4cbecc264801045dd3e3\r\n```\r\n\r\nUnsure about the root cause of this error, but it looks like `C:\\Projects\\RustPython\\target\\wasm32-unknown-unknown\\debug\\rustpython_wasm.wasm` is too big (170+MB) and hence wasm-bindgen is failing with `locals exceed maximum (at offset 18929596)`. This error results in an empty `pkg` directory that breaks `import('rustpython') in `index.js`\r\n\r\n\r\nCurrent workaround is to use the `WasmPackPlugin` in release configuration in `wasm/demo/webpack.conf.js`\r\n```\r\nconfig.plugins.push(\r\n    new WasmPackPlugin({\r\n        crateDirectory: path.resolve(__dirname, '../lib'),\r\n        outDir: path.resolve(__dirname, \"../lib/pkg\"),\r\n        forceMode: \"production\"\r\n    })\r\n);\r\n```","author":{"url":"https://github.com/yashgorana","@type":"Person","name":"yashgorana"},"datePublished":"2022-04-08T10:17:50.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/3592/RustPython/issues/3592"}