a python argcomplete inspired shell completion engine for zig argument parsers.

Traditionally, bash-completion works by command line programs shipping their own bash code to handle suggestions when users type the command and hit <TAB> on the keyboard.

Since these scripts are:

• bash specific
• maintained separately from the binary and might not match the behaviour of it.

Zcomplete instead works like this:

• Generate a separate .wasm version of your program's argument parser
• embed the .wasm in a special zcomplete.wasm ELF section using a linker script
• provides a generic tool called zcomp that needs to be installed in PATH once, along with a simple zcomplete.bash completion script.
• when pressing <TAB> in bash, zcomp will try to extract and instanciate the zcomplete.wasm section with a Webassembly Runtime, then pass in the current command line and the current arg to be completed.
• evaluate the response and generate bash completion
• SUCCESS!

Python's argcomplete works by running the actual python script until the argparse instance is created, and uses the contained info to generate the completion suggestions. It's main shortcomings are:

• needs to run the actual python script. We cannot do that on a native binary safely. It uses a PYTHON_ARGCOMPLETE_OK magic string to determine a script's eligibility for completion.
• May take longer than bearable by users on each <TAB> press, since starting python and reading all source code is slow.

This project is in a Proof-of-concept stage. It barely generates useful completion for itself.

• zsh
• fish
• powershell

• Offer a way for .wasm to query filesystem files?
• report back valid extensions or magic numbers from .wasm to zcomp?

• Embedded Windows Resource files?
• MachO?
• Support .wasm separate from the binary? This needs a reasonably fast way of associating a binary and the .wasm. Optionally, a single .wasm core could serve completions for multiple binaries, like and zcomplete could use the .wasm files like a plugin system.

at the moment we set an explicit generic target (which means only mvp wasm features are on):

.target = b.resolveTargetQuery(.{
    .cpu_arch = .wasm32,
    .os_tag = .freestanding,
    .abi = .none,
    .cpu_model = .{
        .explicit = std.Target.Cpu.Model.generic(.wasm32),
    },
}),

zware works always with 0.14.0, on master with only wasm32-freestanding it fails. Maybe only mvp wasm32 should be supported, but this is the error:

error: ValidatorCallIndirectNoTable
/home/dasimmet/.cache/zig/p/zware-0.0.1-ZA7j6X3jBABhBIltmAF9N6OP7VTsgFP3O1xPkgiaCY_t/src/module/parser.zig:384:68: 0x11c7aec in next (zcomp)
                if (tableidx >= self.module.tables.list.items.len) return error.ValidatorCallIndirectNoTable;
                                                                   ^
/home/dasimmet/.cache/zig/p/zware-0.0.1-ZA7j6X3jBABhBIltmAF9N6OP7VTsgFP3O1xPkgiaCY_t/src/module/parser.zig:63:16: 0x11d9292 in parseFunction (zcomp)
        while (try self.next()) |instr| {
               ^
/home/dasimmet/.cache/zig/p/zware-0.0.1-ZA7j6X3jBABhBIltmAF9N6OP7VTsgFP3O1xPkgiaCY_t/src/module.zig:798:9: 0x11d973a in readFunction (zcomp)
        return parser.parseFunction(funcidx, locals, code);
        ^
/home/dasimmet/.cache/zig/p/zware-0.0.1-ZA7j6X3jBABhBIltmAF9N6OP7VTsgFP3O1xPkgiaCY_t/src/module.zig:686:33: 0x11d9e27 in decodeCodeSection (zcomp)
            const parsed_code = try self.readFunction(module, locals, function_index_start + i);
                                ^
/home/dasimmet/.cache/zig/p/zware-0.0.1-ZA7j6X3jBABhBIltmAF9N6OP7VTsgFP3O1xPkgiaCY_t/src/module.zig:174:22: 0x11dade0 in decodeSection (zcomp)
            .Code => try self.decodeCodeSection(module),
                     ^
/home/dasimmet/.cache/zig/p/zware-0.0.1-ZA7j6X3jBABhBIltmAF9N6OP7VTsgFP3O1xPkgiaCY_t/src/module.zig:106:25: 0x11dba05 in decode (zcomp)
                else => return err,
                        ^
/home/dasimmet/repos/zig/zcomplete/src/zcomp.zig:69:5: 0x11fc840 in complete (zcomp)
    try module.decode();
    ^