go-omni/cmd/go-omni/apigen/mappingLoad.go

package apigen

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"go/importer"
	gotoken "go/token"
	"go/types"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"golang.org/x/mod/modfile"
)

// loadMappingTypes uses the Go compiler's export data, including the pending
// DTOs via an overlay. Module files and sum updates remain in a temporary dir.
// It compiles only explicitly selected packages and their dependencies; never
// runs project code. Build tags/GOOS follow the caller; GOWORK is disabled.
func loadMappingTypes(o Options, refs []string, generated, seeds map[string][]byte) (types.Importer, func(), error) {
	// go list resolves its working directory (notably /var -> /private/var on
	// macOS). Overlay keys must name that same physical path or stale DTOs win.
	o.Dir = canonical(o.Dir)
	temp, err := os.MkdirTemp("", "go-omni-mapping-*")
	if err != nil {
		return nil, nil, err
	}
	cleanup := func() { _ = os.RemoveAll(temp) }
	fail := func(err error) (types.Importer, func(), error) { cleanup(); return nil, nil, err }
	raw, err := os.ReadFile(filepath.Join(o.Dir, "go.mod"))
	if err != nil {
		return fail(errors.New("mapping generation requires an existing Go module; scaffold first and resolve dependencies"))
	}
	mf, err := modfile.Parse("go.mod", raw, nil)
	if err != nil {
		return fail(err)
	}
	replacements := append([]*modfile.Replace(nil), mf.Replace...)
	for _, r := range replacements {
		if r.New.Version == "" && !filepath.IsAbs(r.New.Path) {
			if err = mf.AddReplace(r.Old.Path, r.Old.Version, filepath.Join(o.Dir, r.New.Path), ""); err != nil {
				return fail(err)
			}
		}
	}
	raw, err = mf.Format()
	if err != nil {
		return fail(err)
	}
	modPath := filepath.Join(temp, "go.mod")
	if err = os.WriteFile(modPath, raw, 0600); err != nil {
		return fail(err)
	}
	if sums, e := os.ReadFile(filepath.Join(o.Dir, "go.sum")); e == nil {
		if err = os.WriteFile(filepath.Join(temp, "go.sum"), sums, 0600); err != nil {
			return fail(err)
		}
	} else if !errors.Is(e, os.ErrNotExist) {
		return fail(e)
	}
	overlay := map[string]string{}
	// Hide stale owned Go files, which may otherwise redeclare a renamed DTO.
	var previous manifest
	if data, e := os.ReadFile(filepath.Join(o.Dir, manifestPath)); e == nil {
		if err = json.Unmarshal(data, &previous); err != nil {
			return fail(err)
		}
		for name := range previous.Generated {
			if strings.HasSuffix(name, ".go") {
				if !ownedPath(name) {
					return fail(fmt.Errorf("invalid owned path %s", name))
				}
				if err = safePath(o.Dir, name); err != nil {
					return fail(err)
				}
				if _, ok := generated[name]; !ok {
					overlay[filepath.Join(o.Dir, filepath.FromSlash(name))] = ""
				}
			}
		}
	} else if !errors.Is(e, os.ErrNotExist) {
		return fail(e)
	}
	for i, files := range []map[string][]byte{generated, seeds} {
		names := make([]string, 0, len(files))
		for name := range files {
			if strings.HasSuffix(name, ".go") {
				names = append(names, name)
			}
		}
		sort.Strings(names)
		for _, name := range names {
			if err = safePath(o.Dir, name); err != nil {
				return fail(err)
			}
			path := filepath.Join(o.Dir, filepath.FromSlash(name))
			if i == 1 {
				if _, e := os.Stat(path); e == nil {
					continue
				} else if !errors.Is(e, os.ErrNotExist) {
					return fail(e)
				}
			}
			backing := filepath.Join(temp, fmt.Sprintf("overlay%d.go", len(overlay)))
			if err = os.WriteFile(backing, files[name], 0600); err != nil {
				return fail(err)
			}
			overlay[path] = backing
		}
	}
	raw, err = json.Marshal(map[string]any{"Replace": overlay})
	if err != nil {
		return fail(err)
	}
	overlayPath := filepath.Join(temp, "overlay.json")
	if err = os.WriteFile(overlayPath, raw, 0600); err != nil {
		return fail(err)
	}
	args := []string{"list", "-deps", "-export", "-json", "-mod=readonly", "-modfile", modPath, "-overlay", overlayPath}
	// fmt is used for fallible conversions even if neither struct imports it.
	args = append(args, "fmt")
	args = append(args, refs...)
	ctx, cancel := context.WithTimeout(context.Background(), 90*time.Second)
	defer cancel()
	cmd := exec.CommandContext(ctx, "go", args...)
	cmd.Dir = o.Dir
	cmd.Env = append(os.Environ(), "GOWORK=off")
	cmd.WaitDelay = 2 * time.Second
	stdout := &limitedCatalogBuffer{limit: 32 << 20}
	stderr := &limitedCatalogBuffer{limit: 64 << 10}
	cmd.Stdout = stdout
	cmd.Stderr = stderr
	if err = cmd.Run(); err != nil {
		if ctx.Err() != nil {
			return fail(fmt.Errorf("mapping type loading: %w", ctx.Err()))
		}
		// Go download errors may contain authenticated remote URLs. Keep arbitrary
		// command output out of diagnostics; exact mapping errors follow type loading.
		return fail(fmt.Errorf("mapping type loading failed (%v); run go list -deps -export for the configured source/target/converter packages; check dependencies, build tags and import cycles", err))
	}
	exports := map[string]string{}
	dec := json.NewDecoder(bytes.NewReader(stdout.Bytes()))
	for {
		var p struct {
			ImportPath, Export string
			Error              *struct{ Err string }
		}
		if err = dec.Decode(&p); err == io.EOF {
			break
		} else if err != nil {
			return fail(err)
		}
		if p.Error != nil {
			return fail(fmt.Errorf("mapping package %s could not be compiled", p.ImportPath))
		}
		if p.Export != "" {
			exports[p.ImportPath] = p.Export
		}
	}
	imp := importer.ForCompiler(gotoken.NewFileSet(), "gc", func(path string) (io.ReadCloser, error) {
		file, ok := exports[path]
		if !ok {
			return nil, fmt.Errorf("no export data for mapping dependency %s", path)
		}
		return os.Open(file)
	})
	return imp, cleanup, nil
}