Overview

This proposal outlines the implementation of two standard go test flags for llgo test to improve compatibility with Go tooling.

Flags to Implement

Flag Details

-o file

Compile test binary to the specified file. Test still runs unless -c is specified.

• If file ends in / or is a directory, writes pkg.test in that directory
• Errors when used with multiple packages
• Shared with build command using the existing OutputFile variable

-c

Compile test binary to pkg.test in current directory but do not run it.

• Output location can be changed with -o flag
• Useful for cross-compilation and CI workflows

Design Decisions

Shared Output File Variable

Use the existing OutputFile variable for both build and test commands.

Reason: Simplifies implementation and avoids duplication. The -o flag has the same semantics in both contexts.

Implementation:

func AddTestFlags(fs *flag.FlagSet) {
    fs.StringVar(&OutputFile, "o", "", "Compile test binary to the named file")
    fs.BoolVar(&CompileOnly, "c", false, "Compile test binary but do not run it")
}

Implementation Plan

Modified Files

cmd/internal/flags/flags.go:

• Add CompileOnly variable
• Use existing OutputFile variable (no new variable needed)
• Create AddTestFlags() function
• Update UpdateConfig() for ModeTest

cmd/internal/test/test.go:

• Call flags.AddTestFlags() in init

internal/build/build.go:

• Add CompileOnly field to Config struct

internal/build/run.go:

• Check CompileOnly and skip execution when true

Example Usage

# Compile test binary without running
llgo test -c .

# Compile to specific file
llgo test -c -o mytest.test .

# Compile to specific output and run
llgo test -o mytest.test .

Compatibility

• ✅ All changes are additive and backward compatible
• ✅ Works with embedded targets (e.g., rp2040, wasi)
• ✅ Works with emulator mode
• ✅ No breaking changes to existing behavior

Related

• Comprehensive proposal: Proposal: Add 'go test' Flags Implementation Details #1447 (covers additional flags -args and -json)
• Implementation PR: [CLOSE] Implement go test flags: -o and -c (#1447) #1448

This is a simplified, focused proposal for the core compilation flags. Additional flags (-args, -json) will be proposed separately.