How can I expand arrays / maps when viewing variables in debug mode?

[eeprom-foo]

I'm able to view a listing of variables and their values while debugging with Helix by pressing v. Is there a way to expand entries like Locals > $form: array = array(27) so I can navigate the data within?

[latent-9]

Short answer: you cannot expand them, and it is not a setting you are missing. The variables popup only ever fetches and renders the top level.

dap_variables asks the adapter for the variables of each scope once, then formats each one into a plain text popup. There is a TODO sitting directly above the code that does it:

// TODO: allow expanding variables into sub-fields

helix-term/src/commands/dap.rs:558

The loop below it pushes only name, type and value for each variable (dap.rs:578-589), and the result is turned into a Popup built from Text (dap.rs:593-595). That widget has no selection or fold state, so there is nothing to press a key on even if you wanted to bind one.

The mildly annoying part is that the data needed to recurse is already parsed. Helix's Variable struct deserialises variables_reference (helix-dap-types/src/lib.rs:302), which is exactly the handle you would send back to the adapter to get the children of your $form array. The command reads it for the scope and never for the individual variables.

There is no eval or REPL escape hatch either. The complete DAP command set is 16 commands (helix-term/src/commands.rs:585-600) and none of them evaluate an expression.

The workaround that does work: logpoints

Helix does support breakpoint log messages, and that is the one way to get nested values out today. On the line you care about, press <space>G then Ctrl-l (dap_edit_log, bound in helix-term/src/keymap/default.rs:251) and type a message. It is stored as that breakpoint's log_message (dap.rs:713) and passed to the adapter as the DAP logMessage, so execution does not stop and the text goes to your debug output.

Most adapters interpolate {expr} inside that string, so something like

form[0] is {$form[0]}

will print the expanded value. Interpolation is optional in the DAP spec, so it depends on your adapter. If nothing shows up, that is why.

One thing that probably cost you time before you asked: the book has no debugger page at all, so there was nothing to find. The DAP support is undocumented outside the source and the keymap.

Checked against master at 079a789.