denoland-deno/docs/contributing/development_tools.md

## Testing and Tools

### Tests

Test `deno`:

```shell
# Run the whole suite:
cargo test

# Only test cli/js/:
cargo test js_unit_tests
```

Test `std/`:

```shell
cargo test std_tests
```

### Lint and format

Lint the code:

```shell
./tools/lint.py
```

Format the code:

```shell
./tools/format.py
```

### Profiling

To start profiling,

```sh
# Make sure we're only building release.
# Build deno and V8's d8.
ninja -C target/release d8

# Start the program we want to benchmark with --prof
./target/release/deno run tests/http_bench.ts --allow-net --v8-flags=--prof &

# Exercise it.
third_party/wrk/linux/wrk http://localhost:4500/
kill `pgrep deno`
```

V8 will write a file in the current directory that looks like this:
`isolate-0x7fad98242400-v8.log`. To examine this file:

```sh
D8_PATH=target/release/ ./third_party/v8/tools/linux-tick-processor
isolate-0x7fad98242400-v8.log > prof.log
# on macOS, use ./third_party/v8/tools/mac-tick-processor instead
```

`prof.log` will contain information about tick distribution of different calls.

To view the log with Web UI, generate JSON file of the log:

```sh
D8_PATH=target/release/ ./third_party/v8/tools/linux-tick-processor
isolate-0x7fad98242400-v8.log --preprocess > prof.json
```

Open `third_party/v8/tools/profview/index.html` in your browser, and select
`prof.json` to view the distribution graphically.

Useful V8 flags during profiling:

- --prof
- --log-internal-timer-events
- --log-timer-events
- --track-gc
- --log-source-code
- --track-gc-object-stats

To learn more about `d8` and profiling, check out the following links:

- [https://v8.dev/docs/d8](https://v8.dev/docs/d8)
- [https://v8.dev/docs/profile](https://v8.dev/docs/profile)

### Debugging with LLDB

We can use LLDB to debug Deno.

```shell
$ lldb -- target/debug/deno run tests/worker.js
> run
> bt
> up
> up
> l
```

To debug Rust code, we can use `rust-lldb`. It should come with `rustc` and is a
wrapper around LLDB.

```shell
$ rust-lldb -- ./target/debug/deno run --allow-net tests/http_bench.ts
# On macOS, you might get warnings like
# `ImportError: cannot import name _remove_dead_weakref`
# In that case, use system python by setting PATH, e.g.
# PATH=/System/Library/Frameworks/Python.framework/Versions/2.7/bin:$PATH
(lldb) command script import "/Users/kevinqian/.rustup/toolchains/1.36.0-x86_64-apple-darwin/lib/rustlib/etc/lldb_rust_formatters.py"
(lldb) type summary add --no-value --python-function lldb_rust_formatters.print_val -x ".*" --category Rust
(lldb) type category enable Rust
(lldb) target create "../deno/target/debug/deno"
Current executable set to '../deno/target/debug/deno' (x86_64).
(lldb) settings set -- target.run-args  "tests/http_bench.ts" "--allow-net"
(lldb) b op_start
(lldb) r
```

### V8 flags

V8 has many many internal command-line flags.

```shell
# list available v8 flags
$ deno --v8-flags=--help

#  example for applying multiple flags
$ deno --v8-flags=--expose-gc,--use-strict
```

Particularly useful ones:

```
--async-stack-trace
```

### Continuous Benchmarks

See our benchmarks [over here](https://deno.land/benchmarks)

The benchmark chart supposes
https://github.com/denoland/benchmark_data/blob/gh-pages/data.json has the type
`BenchmarkData[]` where `BenchmarkData` is defined like the below:

```ts
interface ExecTimeData {
  mean: number;
  stddev: number;
  user: number;
  system: number;
  min: number;
  max: number;
}

interface BenchmarkData {
  created_at: string;
  sha1: string;
  benchmark: {
    [key: string]: ExecTimeData;
  };
  binarySizeData: {
    [key: string]: number;
  };
  threadCountData: {
    [key: string]: number;
  };
  syscallCountData: {
    [key: string]: number;
  };
}
```