debugging.md

Debugging Duffle using VS Code

We can use VS Code to breakpoint debug the Duffle binary. For this, you need:

• VS Code
• the Go extension for VS Code
• the Delve debugger

There is a wiki on the VS Code Go extension repository about debugging Go code using VS Code and Delve.

There are two modes for debugging Go code in VS Code that are relevant for us:

• debug - rebuilds the binary on every new run
• exec - uses an already built binary, launches it and attaches the debugger

For this document, we are going to use the exec mode, simply because we already have a customized way of building the Duffle binary (using make), and we might want to iterate through the execution of a command multiple times without rebuilding the binary.

Here are the steps involved in doing breakpoint debugging:

• make debug - this will build the Duffle binary and include the debugging symbols
• edit .vscode/launch.json and in the args field add the Duffle command you want to debug, while passing each argument as a new string.
• add a breakpoint in cmd/duffle/install

For example:

$ duffle install debug-test --driver debug -f examples/helloworld/cnab/bundle.json is translated into

"args": [
    "install", "debug-test", "--driver", "debug", "-f", "${workspaceFolder}/examples/helloworld/cnab/bundle.json"
]

Things to note regarding the path:

• because the examples directory is at the root of the repo, the ${workspaceFolder} variable is need to avoid passing the absolute path
• if running on Windows, the path separator must be \\, so the above path becomes ${workspaceFolder}\\examples\\helloworld\\cnab\\bundle.json
• you can find the full example for both Windows and Unix in .vscode/launch.json