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Debugging

Debugging with VS Code

Install go install github.com/go-delve/delve/cmd/dlv@latest
Install VS Code extension rust-analyzer and CodeLLDB
build @rspack/cli and napi binding by run pnpm install && pnpm -w build:cli:debug
In VS Code's Run and Debug tab, select debug-rspack to start debugging the initial launch of @rspack/cli. This task can be configured in .vscode/launch.json, which launches the Node and Rust debugger together.

Tracing

tracing is used to instrumenting Rspack.

The supported tracing levels for

release builds are INFO, WARN and ERROR
debug builds are TRACE, DEBUG, INFO, WARN and ERROR

Use the RSPACK_PROFILE environment variable for displaying trace information

RSPACK_PROFILE=TRACE=layer=logger rspack build
# filter for an event
RSPACK_PROFILE='TRACE=layer=logger&filter=rspack_core::compiler::compilation' rspack build
# with logger level
RSPACK_PROFILE='TRACE=layer=logger&filter=rspack_core::compiler::compilation=info' rspack build
# filter logs across multiple modules
RSPACK_PROFILE='TRACE=layer=logger&filter=rspack_core::compiler::compilation,rspack_core::build_chunk_graph::code_splitter' rspack build
# [fn_name] will show:
# - all functions calls to `fn_name`
# - the arguments(except for these in the `skip` list)
# - everything until this function returns
RSPACK_PROFILE='TRACE=layer=logger&filter=[build_chunk_graph]' rspack build
# compilation::chunk_asset is a custom instrument name
RSPACK_PROFILE='TRACE=layer=logger&filter=[compilation:chunk_asset]' rspack build
# log a specific function by their arguments
RSPACK_PROFILE='TRACE=layer=logger&filter=[compilation:chunk_asset{filename="main\.js"}]' rspack build
# It support regexp expression
RSPACK_PROFILE='TRACE=layer=logger&filter=[compilation:chunk_asset{filename=".*\.js"}]' rspack build
# disable ansi color escape codes
NO_COLOR=1 RSPACK_PROFILE=TRACE=layer=logger rspack build

Resolver

oxc_resolver emits some tracing information for debugging purposes.

RSPACK_PROFILE='TRACE=filter=oxc_resolver=trace&layer=logger' rspack build

rust-lldb

rust-lldb can be used to get panic information from debug builds

rust-lldb -- node /path/to/rspack build

Once it launches, press r for running the program.

For example, examples/arco-pro crashes without any information before this fix:

rspack/examples/arco-pro ❯ node ../../packages/rspack-cli/bin/rspack build
Rspack ██████████████████████░░░░░░░░░░░░░░░░░░ 56% building ./pages/welcome
zsh: bus error  node ../../packages/rspack-cli/bin/rspack build

Using rust-lldb

rspack/examples/arco-pro ❯ rust-lldb -- node ../../packages/rspack-cli/bin/rspack build

Press r and it prints:

Process 23110 stopped
* thread #10, name = 'tokio-runtime-worker', stop reason = EXC_BAD_ACCESS (code=2, address=0x70000cc66560)
    frame #0: 0x0000000140d0db4b rspack.darwin-x64.node`swc_ecma_parser::parser::expr::ops::_$LT$impl$u20$swc_ecma_parser..parser..Parser$LT$I$GT$$GT$::parse_unary_expr::h29f49330a806839c(self=0x0000000000000000) at ops.rs:244
   241 	    /// Parse unary expression and update expression.
   242 	    ///
   243 	    /// spec: 'UnaryExpression'
-> 244 	    pub(in crate::parser) fn parse_unary_expr(&mut self) -> PResult<Box<Expr>> {
   245 	        trace_cur!(self, parse_unary_expr);
   246 	        let start = cur_pos!(self);
   247
Target 0: (node) stopped.

Mixed Debug

This section aims to illustrate the method for mixed debugging between JavaScript and Rust.

Prerequisites

To illustrate this process, I'll use an example. Let's start by introduce the environment and example I have used.

System: macos
IDE: vscode
Debugging target: rspack build ${projectRoot}/basic

Firstly, you need to build rspack in debug mode. To do this, execute the following commands in the project's root directory:

npm run build:binding:debug
npm run build:js

Configure `launch.json` in VS Code

It's necessary to configure two debug configurations within in .vscode/launch.json.

attach for node:

{
  "name": "attach:node",
  "request": "attach", // refer: https://code.visualstudio.com/docs/editor/debugging#_launch-versus-attach-configurations
  "type": "node",
  // `9229` is the default port of message
  "port": 9229,
}

and launch for lldb

{
  "name": "launch:rust-from-node",
  "request": "launch",
  "type": "lldb", // it means we use `lldb` to launch the binary file of `node`
  "program": "node",
  "args": [
    "--inspect",
    "--enable-source-maps",
    "${workspaceFolder}/packages/rspack-cli/bin/rspack",
    "build",
    "-c",
    "${workspaceFolder}/examples/basic/rspack.config.js",
  ],
  // `cwd` is just for repack find the correctly entry.
  "cwd": "${workspaceFolder}/examples/basic/",
}

Next, we can utilize compounds to amalgamate the two commands:

{
  "name": "mix-debug",
  "configurations": ["attach:node", "launch:rust-from-node"]
}

Finally, your launch.json should appear as follows:

{
  "configurations": [
    {
      "name": "attach:node",
      "request": "attach",
      "type": "node",
      "port": 9229
    },
    {
      "name": "launch:rust-from-node",
      "request": "launch",
      "type": "lldb",
      "program": "node",
      "args": [
        "--inspect",
        "--enable-source-maps",
        "${workspaceFolder}/packages/rspack-cli/bin/rspack",
        "build",
        "-c",
        "${workspaceFolder}/examples/basic/rspack.config.js"
      ],
      "cwd": "${workspaceFolder}/examples/basic/"
    }
  ],
  "compounds": [
    {
      "name": "mix-debug",
      "configurations": ["attach:node", "launch:rust-from-node"]
    }
  ]
}

Debugging Attempt

Next, we can introduce some breakpoints and commence debugging.

The result appears as follows:

ON THIS PAGE

Debugging#

Debugging with VS Code#

Tracing#

Resolver#

rust-lldb#

Mixed Debug#

Prerequisites#

Configure launch.json in VS Code#

Debugging Attempt#