feat(cli): add target-os and target-arch flags for neva build c…

…md; add `neva osarch` command that prints output of the `go tool

cmd/neva/main.go

@@ -20,7 +20,7 @@ import (
 )
 
 func main() {
-	wd, err := os.Getwd()
+	workdir, err := os.Getwd()
 	if err != nil {
 		panic(err)
 	}
@@ -53,9 +53,7 @@ func main() {
 		&desugarer,
 		analyzer,
 		irgen,
-		native.NewBackend(
-			golangBackend,
-		),
+		native.NewBackend(golangBackend),
 	)
 
 	wasmCompiler := compiler.New(
@@ -64,9 +62,7 @@ func main() {
 		&desugarer,
 		analyzer,
 		irgen,
-		wasm.NewBackend(
-			golangBackend,
-		),
+		wasm.NewBackend(golangBackend),
 	)
 
 	jsonCompiler := compiler.New(
@@ -89,7 +85,7 @@ func main() {
 
 	// command-line app that can compile and interpret neva code
 	app := cli.NewApp(
-		wd,
+		workdir,
 		bldr,
 		goCompiler,
 		nativeCompiler,

docs/tutorial.md

@@ -129,6 +129,8 @@ This will produce an `output` file in the directory where neva-cli was executed,
 
 Once again you should see `Hello, World!`.
 
+> Execute `neva build --help` to learn more - how to compile to Go, WASM or how to do cross-compilation e.g. compile linux binaries in windows.
+
 ## Core Concepts
 
 ### Components

internal/cli/build.go

@@ -2,6 +2,7 @@ package cli
 
 import (
 	"fmt"
+	"os"
 
 	"github.com/nevalang/neva/internal/compiler"
 
@@ -18,7 +19,7 @@ func newBuildCmd(
 ) *cli.Command {
 	return &cli.Command{
 		Name:  "build",
-		Usage: "Build neva program from source code",
+		Usage: "Generate target platform code from neva program",
 		Args:  true,
 		Flags: []cli.Flag{
 			&cli.StringFlag{
@@ -31,7 +32,7 @@ func newBuildCmd(
 			},
 			&cli.StringFlag{
 				Name:  "target",
-				Usage: "Target platform for build (options: go, wasm, native, json, dot)",
+				Usage: "Target platform for build (options: go, wasm, native, json, dot). For 'native' target, 'target-os' and 'target-arch' flags can be used, but if used, they must be used together.",
 				Action: func(ctx *cli.Context, s string) error {
 					switch s {
 					case "go", "wasm", "native", "json", "dot":
@@ -40,24 +41,52 @@ func newBuildCmd(
 					return fmt.Errorf("Unknown target %s", s)
 				},
 			},
+			&cli.StringFlag{
+				Name:  "target-os",
+				Usage: "Target operating system for native build. See 'neva osarch' for supported combinations. Only supported for native target. Not needed if building for the current platform. Must be combined properly with 'target-arch'.",
+			},
+			&cli.StringFlag{
+				Name:  "target-arch",
+				Usage: "Target architecture for native build. See 'neva osarch' for supported combinations. Only supported for native target. Not needed if building for the current platform. Must be combined properly with 'target-os'.",
+			},
 		},
 		ArgsUsage: "Provide path to main package",
 		Action: func(cliCtx *cli.Context) error {
+			var target string
+			if cliCtx.IsSet("target") {
+				target = cliCtx.String("target")
+			} else {
+				target = "native"
+			}
+
+			switch target {
+			case "go", "wasm", "json", "dot", "native":
+			default:
+				return fmt.Errorf("Unknown target %s", target)
+			}
+
+			var targetOS, targetArch string
+			if cliCtx.IsSet("target-os") {
+				targetOS = cliCtx.String("target-os")
+			}
+			if cliCtx.IsSet("target-arch") {
+				targetArch = cliCtx.String("target-arch")
+			}
+			if (targetOS != "" && targetArch == "") || (targetOS == "" && targetArch != "") {
+				return fmt.Errorf("target-os and target-arch must be set together")
+			}
+			if target != "native" && targetOS != "" {
+				return fmt.Errorf("target-os and target-arch are only supported when target is native")
+			}
+
 			mainPkg, err := mainPkgPathFromArgs(cliCtx)
 			if err != nil {
 				return err
 			}
 
-			output := workdir
+			outputDirPath := workdir
 			if cliCtx.IsSet("output") {
-				output = cliCtx.String("output")
-			}
-
-			var target string
-			if cliCtx.IsSet("target") {
-				target = cliCtx.String("target")
-			} else {
-				target = "native"
+				outputDirPath = cliCtx.String("output")
 			}
 
 			var isTraceEnabled bool
@@ -67,7 +96,7 @@ func newBuildCmd(
 
 			compilerInput := compiler.CompilerInput{
 				Main:   mainPkg,
-				Output: output,
+				Output: outputDirPath,
 				Trace:  isTraceEnabled,
 			}
 
@@ -83,8 +112,27 @@ func newBuildCmd(
 				compilerToUse = compilerToDOT
 			case "native":
 				compilerToUse = compilerToNative
-			default:
-				return fmt.Errorf("Unknown target %s", target)
+			}
+
+			if targetOS != "" {
+				prevGOOS := os.Getenv("GOOS")
+				prevGOARCH := os.Getenv("GOARCH")
+
+				if err := os.Setenv("GOOS", targetOS); err != nil {
+					return fmt.Errorf("set GOOS: %w", err)
+				}
+				if err := os.Setenv("GOARCH", targetArch); err != nil {
+					return fmt.Errorf("set GOARCH: %w", err)
+				}
+
+				defer func() {
+					if err := os.Setenv("GOOS", prevGOOS); err != nil {
+						panic(err)
+					}
+					if err := os.Setenv("GOARCH", prevGOARCH); err != nil {
+						panic(err)
+					}
+				}()
 			}
 
 			return compilerToUse.Compile(cliCtx.Context, compilerInput)

internal/cli/cli.go

@@ -33,6 +33,7 @@ func NewApp(
 			newGetCmd(workdir, bldr),
 			newRunCmd(workdir, nativec),
 			newBuildCmd(workdir, goc, nativec, wasmc, jsonc, dotc),
+			newOSArchCmd(),
 		},
 	}
 }

internal/cli/osarch.go

@@ -0,0 +1,34 @@
+package cli
+
+import (
+	"fmt"
+	"os/exec"
+	"strings"
+
+	cli "github.com/urfave/cli/v2"
+)
+
+func newOSArchCmd() *cli.Command {
+	return &cli.Command{
+		Name:  "osarch",
+		Usage: "List supported OS/architecture combinations for native target",
+		Action: func(cliCtx *cli.Context) error {
+			cmd := exec.Command("go", "tool", "dist", "list")
+			output, err := cmd.Output()
+			if err != nil {
+				return fmt.Errorf("failed to execute go tool dist list: %w", err)
+			}
+
+			fmt.Println("Supported OS/architecture combinations for native target:")
+			fmt.Println("(use these values for --target-os and --target-arch flags when cross-compiling)")
+			fmt.Println()
+
+			platforms := strings.Split(strings.TrimSpace(string(output)), "\n")
+			for _, platform := range platforms {
+				fmt.Println(platform)
+			}
+
+			return nil
+		},
+	}
+}