integrations/golang: Use full package paths when building.

Carefully tracking the path to the built package within the Go module allows us to refer to binaries in a build plan across modules.

Previously given the following specification in example.com/foo/xxx/binary.cue

    build_plan: [{binary: "example.com/bar/yyy"}]

we would try to build a package with the desired local name (yyy), but within the "calling" module (example.com/foo/yyy).

internal/integrations/golang/buildkit.go

@@ -7,6 +7,7 @@ package golang
 import (
 	"context"
 	"fmt"
+	"path"
 	"strings"
 
 	"github.com/moby/buildkit/client/llb"
@@ -73,12 +74,9 @@ func buildUsingBuildkit(ctx context.Context, env pkggraph.SealedContext, bin GoB
 	goBuild = append(goBuild, quoteArgs(goBuildArgs(version, bin.StripBinary))...)
 	goBuild = append(goBuild, fmt.Sprintf("-o=/out/%s", bin.BinaryName))
 
-	relPath, err := makePkg(bin.GoWorkspacePath, bin.SourcePath)
-	if err != nil {
-		return nil, err
-	}
+	pkg := path.Join(bin.GoModule, bin.SourcePath)
 
-	goBuild = append(goBuild, relPath)
+	goBuild = append(goBuild, pkg)
 
 	state := (llbutil.RunGo{
 		Base:       prepareGoMod(base, src, conf.TargetPlatform()).Root(),

internal/integrations/golang/generate.proto

@@ -20,4 +20,7 @@ message FrameworkExt {
 
     // Relative path to go.work, or to go.mod.
     string go_workspace_path = 4;
+
+    // Path to the Go package within the module.
+    string rel_package = 5;
 }

internal/integrations/golang/gobinary.go

@@ -28,7 +28,7 @@ type GoBinary struct {
 	GoWorkspacePath string `json:"workspacePath"`
 	GoModule        string `json:"module"` // Go module name.
 	GoVersion       string `json:"goVersion"`
-	SourcePath      string `json:"sourcePath"` // Relative to ns workspace root.
+	SourcePath      string `json:"sourcePath"` // Relative to GoModule.
 	BinaryName      string `json:"binaryName"`
 
 	BinaryOnly      bool
@@ -59,6 +59,11 @@ func FromLocation(loc pkggraph.Location, pkgName string) (*GoBinary, error) {
 		return nil, err
 	}
 
+	pkgInsideMod, err := filepath.Rel(filepath.Dir(modFile), absSrc)
+	if err != nil {
+		return nil, err
+	}
+
 	gowork, _ := findroot.Find("go work", filepath.Dir(modFile), findroot.LookForFile("go.work"))
 	if gowork == "" {
 		gowork = filepath.Dir(modFile)
@@ -73,7 +78,7 @@ func FromLocation(loc pkggraph.Location, pkgName string) (*GoBinary, error) {
 		PackageName:     loc.PackageName,
 		GoWorkspacePath: relMod,
 		GoModule:        mod.Module.Mod.Path,
-		SourcePath:      loc.Rel(pkgName),
+		SourcePath:      pkgInsideMod,
 		GoVersion:       mod.Go.Version,
 	}, nil
 }

internal/integrations/golang/golang.go

@@ -93,7 +93,7 @@ func (impl) PrepareBuild(ctx context.Context, _ assets.AvailableBuildAssets, ser
 		GoWorkspacePath: ext.GoWorkspacePath,
 		GoModule:        ext.GoModule,
 		GoVersion:       ext.GoVersion,
-		SourcePath:      server.Location.Rel(),
+		SourcePath:      ext.RelPackage,
 		BinaryName:      serverName(server),
 	}
 
@@ -222,6 +222,7 @@ func (impl) PreParseServer(ctx context.Context, loc pkggraph.Location, ext *pars
 		GoVersion:       bin.GoVersion,
 		GoModule:        bin.GoModule,
 		GoWorkspacePath: bin.GoWorkspacePath,
+		RelPackage:      bin.SourcePath,
 	})
 	if err != nil {
 		return err

internal/integrations/golang/localbuild.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"io/fs"
 	"os"
+	"path"
 	"path/filepath"
 
 	specs "github.com/opencontainers/image-spec/specs-go/v1"
@@ -100,10 +101,7 @@ func compile(ctx context.Context, sdk golang.LocalSDK, absWorkspace string, targ
 
 	modulePath := filepath.Join(absWorkspace, bin.GoWorkspacePath)
 	out := filepath.Join(targetDir, bin.BinaryName)
-	pkg, err := makePkg(bin.GoWorkspacePath, bin.SourcePath)
-	if err != nil {
-		return err
-	}
+	pkg := path.Join(bin.GoModule, bin.SourcePath)
 
 	var cmd localexec.Command
 	cmd.Label = "go build"