How to debug live code

How to debug a program with Visual Studio Code:

Debug TypeScript code

Requires “Debugger for Chrome” extension.

  • Quit Chrome
  • Launch Chrome (Canary) from the command line with a remote debugging port:
    • Mac OS: /Applications/Google\ Chrome\ Canary.app/Contents/MacOS/Google\ Chrome\ Canary --remote-debugging-port=9222
    • Windows: start chrome.exe –remote-debugging-port=9222
    • Linux: chromium-browser --remote-debugging-port=9222
  • Go to http://localhost:3080
  • Open the Debugger in VSCode: “View” > “Debug”
  • Launch the (ui) http://localhost:3080/* debug configuration
  • Set breakpoints, enjoy

Debug Go code

Install Delve:

xcode-select --install
pushd /tmp
go get github.com/go-delve/delve/cmd/dlv
popd /tmp

Then install pgrep:

brew install proctools

Make sure to run env DELVE=true dev/start.sh to disable optimizations during compilation, otherwise Delve will have difficulty stepping through optimized functions (line numbers will be off, you won’t be able to print local variables, etc.).

Now you can attach a debugger to any Go process (e.g. frontend, searcher, go-langserver) in 1 command:

dlv attach $(pgrep frontend)

Delve will pause the process once it attaches the debugger. Most used commands:

  • b internal/db/access_tokens.go:52 to set a breakpoint on a line (bp lists all, clearall deletes all)
  • c to continue execution of the program
  • Ctrl-C pause the program to bring back the command prompt
  • n to step over the next statement
  • s to step into the next function call
  • stepout to step out of the current function call
  • Ctrl-D to exit