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| 1 | +// Package structs provides code generation utilities for optimizing Go struct |
| 2 | +// types. The primary use case is flattening deeply nested API model structs |
| 3 | +// into decode-efficient versions where nested struct fields are replaced with |
| 4 | +// map[string]any, eliminating the decode -> allocate -> re-encode cycle that occurs |
| 5 | +// when the CloudQuery SDK serializes nested fields as JSON columns. |
| 6 | +package structs |
| 7 | + |
| 8 | +import ( |
| 9 | + "bytes" |
| 10 | + "embed" |
| 11 | + "errors" |
| 12 | + "fmt" |
| 13 | + "go/ast" |
| 14 | + "go/format" |
| 15 | + "os" |
| 16 | + "path/filepath" |
| 17 | + "slices" |
| 18 | + "strings" |
| 19 | + "text/template" |
| 20 | +) |
| 21 | + |
| 22 | +//go:embed templates/*.go.tpl |
| 23 | +var templatesFS embed.FS |
| 24 | + |
| 25 | +var tmpl = template.Must(template.ParseFS(templatesFS, "templates/*.go.tpl")) |
| 26 | + |
| 27 | +// StructConfig defines how to transform one source struct into an optimized version. |
| 28 | +type StructConfig struct { |
| 29 | + // SourceName is the struct name in the source file (e.g. "VulnerabilityFinding"). |
| 30 | + SourceName string |
| 31 | + // OutputName is the generated struct name (e.g. "customVulnerabilityFinding"). |
| 32 | + OutputName string |
| 33 | + // OutputFile is the filename for the generated file (e.g. "vulnerability_finding_generated.go"). |
| 34 | + OutputFile string |
| 35 | + // ExtraFields are additional fields prepended to the generated struct. |
| 36 | + ExtraFields []Field |
| 37 | +} |
| 38 | + |
| 39 | +// Field represents a struct field in the generated output. |
| 40 | +type Field struct { |
| 41 | + Name string |
| 42 | + Type string |
| 43 | + JSONTag string |
| 44 | +} |
| 45 | + |
| 46 | +type templateData struct { |
| 47 | + HeaderComment string |
| 48 | + PackageName string |
| 49 | + SourceName string |
| 50 | + OutputName string |
| 51 | + Fields []Field |
| 52 | +} |
| 53 | + |
| 54 | +// Flatten parses the Go source file at srcPath, finds the structs described by |
| 55 | +// configs, replaces deeply nested struct fields with map[string]any, and writes |
| 56 | +// generated files into outputDir. |
| 57 | +// |
| 58 | +// Scalar types and string-based enum types |
| 59 | +// are kept typed. All other types (structs, interfaces, cross-package types, |
| 60 | +// maps) are flattened to map[string]any. Pointer wrappers are preserved for |
| 61 | +// scalar types but collapsed for complex types. |
| 62 | +func Flatten(srcPath string, configs []StructConfig, outputDir string, opts ...Option) error { |
| 63 | + var o options |
| 64 | + for _, opt := range opts { |
| 65 | + opt(&o) |
| 66 | + } |
| 67 | + o.setDefaults(outputDir) |
| 68 | + |
| 69 | + f, err := parseFile(srcPath) |
| 70 | + if err != nil { |
| 71 | + return err |
| 72 | + } |
| 73 | + |
| 74 | + typeKinds := buildTypeKinds(f) |
| 75 | + scalars := o.scalars() |
| 76 | + |
| 77 | + var errs []error |
| 78 | + for _, cfg := range configs { |
| 79 | + if err := flattenOne(f, cfg, typeKinds, scalars, outputDir, &o); err != nil { |
| 80 | + errs = append(errs, fmt.Errorf("%s: %w", cfg.SourceName, err)) |
| 81 | + } |
| 82 | + } |
| 83 | + return errors.Join(errs...) |
| 84 | +} |
| 85 | + |
| 86 | +func flattenOne(f *ast.File, cfg StructConfig, typeKinds map[string]string, scalars map[string]bool, outputDir string, o *options) error { |
| 87 | + st, err := findStruct(f, cfg.SourceName) |
| 88 | + if err != nil { |
| 89 | + return err |
| 90 | + } |
| 91 | + |
| 92 | + fields := make([]Field, 0, len(cfg.ExtraFields)+len(st.Fields.List)) |
| 93 | + fields = append(fields, cfg.ExtraFields...) |
| 94 | + sourceFields := extractFields(st, typeKinds, scalars) |
| 95 | + if o.sortFields { |
| 96 | + sortFields(sourceFields) |
| 97 | + } |
| 98 | + fields = append(fields, sourceFields...) |
| 99 | + |
| 100 | + data := templateData{ |
| 101 | + HeaderComment: o.headerComment, |
| 102 | + PackageName: o.packageName, |
| 103 | + SourceName: cfg.SourceName, |
| 104 | + OutputName: cfg.OutputName, |
| 105 | + Fields: fields, |
| 106 | + } |
| 107 | + |
| 108 | + var buf bytes.Buffer |
| 109 | + if err := tmpl.ExecuteTemplate(&buf, "struct.go.tpl", data); err != nil { |
| 110 | + return fmt.Errorf("executing template: %w", err) |
| 111 | + } |
| 112 | + |
| 113 | + formatted, err := format.Source(buf.Bytes()) |
| 114 | + if err != nil { |
| 115 | + fmt.Fprintf(os.Stderr, "warning: could not format generated code for %s: %v\n", cfg.OutputFile, err) |
| 116 | + formatted = buf.Bytes() |
| 117 | + } |
| 118 | + |
| 119 | + outputPath := filepath.Join(outputDir, cfg.OutputFile) |
| 120 | + if err := os.MkdirAll(filepath.Dir(outputPath), 0o755); err != nil { |
| 121 | + return fmt.Errorf("creating output directory: %w", err) |
| 122 | + } |
| 123 | + if err := os.WriteFile(outputPath, formatted, 0o644); err != nil { |
| 124 | + return fmt.Errorf("writing %s: %w", outputPath, err) |
| 125 | + } |
| 126 | + |
| 127 | + fmt.Printf("Generated %s with %d fields\n", outputPath, len(fields)) |
| 128 | + return nil |
| 129 | +} |
| 130 | + |
| 131 | +// sortFields sorts fields with "ID" first, then alphabetically by name (case-insensitive). |
| 132 | +func sortFields(fields []Field) { |
| 133 | + slices.SortStableFunc(fields, func(a, b Field) int { |
| 134 | + aIsID := strings.EqualFold(a.Name, "ID") |
| 135 | + bIsID := strings.EqualFold(b.Name, "ID") |
| 136 | + switch { |
| 137 | + case aIsID && !bIsID: |
| 138 | + return -1 |
| 139 | + case !aIsID && bIsID: |
| 140 | + return 1 |
| 141 | + default: |
| 142 | + return strings.Compare(strings.ToLower(a.Name), strings.ToLower(b.Name)) |
| 143 | + } |
| 144 | + }) |
| 145 | +} |
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