Developer FAQ

This is just getting started. It will absorb some of the other Developer docs.

How do I get/build the hledger source ?

$ git clone
$ stack build

You can specify hledger, hledger-ui or hledger-web as an argument to build just that executable. Please see Install > Build from source for more details and other build methods.

What other repos are there ?

There are three official repos:

And third-party add-ons and tools (hledger-iadd, hledger-utils, full fledged hledger, hledger-flow, etc.) have their own repos.

How do I run a build in place ?

After building with stack,

$ stack exec -- hledger [ARGS]    # or hledger-ui, hledger-web

Or after building with cabal,

$ cabal exec -- hledger [ARGS]

How do I install a build in PATH ?

$ stack install

This installs the hledger executables to ~/.local/bin. You should have this directory configured in $PATH. Or you can install to another directory with --local-bin-path. It builds the executables first if needed; see Install > Build from source for more about building. You can specify hledger, hledger-ui or hledger-web as an argument to build/install just that executable.

If you use cabal, it has a similar command; the argument is required. It will install executables to ~/.cabal/bin:

$ cabal install all:exes

How do I build/run with ghc-debug support ?

You might need to stop background builders like HLS, to avoid a fight over the build flag (in VS Code, run the command "Haskell: Stop Haskell LSP server").

Then build lib and executable(s) with the ghcdebug flag:

$ stack build --flag='*:ghcdebug'

When the build is right, --version should mention ghc-debug:

$ stack exec -- hledger --version
... with ghc debug support

And when you run at debug level -1, -2 or -3 the output should mention ghc-debug:

$ hledger CMD --debug=-1    # run normally, and listen for ghc-debug commands
$ hledger CMD --debug=-2    # pause for ghc-debug commands at program start (doesn't work)
$ hledger CMD --debug=-3    # pause for ghc-debug commands at program end (doesn't work)
Starting ghc-debug on socket: ...

Now in another window, you can run ghc-debug-brick and it will show the hledger process (until it ends). Press enter to connect. If it fails,

  • you might need to clear out stale sockets: rm -f ~/.local/share/ghc-debug/debuggee/sockets/*
  • you might need to kill stale hledger processes: pkill -fl hledger
  • with --debug=-2 or -3 it fails with rts_resume: called from a different OS thread than rts_pause, so use --debug=-1 instead. This works best with the long-running hledger-ui or hledger-web; with hledger, you'll need a big enough data file so that you have time to connect before it finishes. Once connected, press p to pause the program.

At this point, you can explore memory/profile information, save snapshots, resume execution, etc.

Or, instead of ghc-debug-brick you can write a ghc-debug-client script to extract specific information.