loader.go

package gatekit

import (
	"encoding/json"
	"os"
	"path/filepath"
	"strings"
	"time"
)

// loadedSource pairs a parsed Source with the file-level facts Evaluate
// needs but that don't belong in the JSON schema itself: the file's own
// mtime (the freshness signal a module cannot lie about) and whether it
// parsed at all.
type loadedSource struct {
	Source
	mtime   time.Time
	parsed  bool
	warning string // set when parsed is false, or the module field mismatches
}

// loadSources reads every sources/*.json file in dir. A file that fails to
// parse is never fatal to the whole Evaluate call -- it becomes a
// loadedSource with parsed=false, zero items, and a warning, so one broken
// module can never take down every other module's reporting.
func loadSources(dir string) ([]loadedSource, error) {
	entries, err := os.ReadDir(dir)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, err
	}

	var out []loadedSource
	for _, e := range entries {
		if e.IsDir() || !strings.HasSuffix(e.Name(), ".json") {
			continue
		}
		path := filepath.Join(dir, e.Name())
		stem := strings.TrimSuffix(e.Name(), ".json")

		info, err := e.Info()
		if err != nil {
			continue // vanished between ReadDir and Info; next Evaluate will see it or not
		}

		ls := loadedSource{mtime: info.ModTime()}
		b, err := os.ReadFile(path)
		if err != nil {
			ls.Module = stem
			ls.warning = stem + ": could not read source file: " + err.Error()
			out = append(out, ls)
			continue
		}
		var s Source
		if err := json.Unmarshal(b, &s); err != nil {
			ls.Module = stem
			ls.warning = stem + ": could not parse source file: " + err.Error()
			out = append(out, ls)
			continue
		}

		ls.Source = s
		ls.parsed = true
		if s.Module == "" {
			ls.Module = stem
		} else if s.Module != stem {
			ls.warning = "source file " + e.Name() + " declares module \"" + s.Module +
				"\", which does not match its filename; grouping by filename"
			ls.Module = stem
		}
		out = append(out, ls)
	}
	return out, nil
}