Codegen: Render constraints in generated docs (#63196)

* Add constraints rendering

* Generate docs

* Fix constraint format

* Add type alias

* Compare numbers as strings

* fixup! Compare numbers as strings

* Add missing return

pkg/codegen/jenny_docs.go

@@ -60,7 +60,9 @@ func (j docsJenny) Generate(kind kindsys.Kind) (*codejen.File, error) {
 			Schemas json.RawMessage
 		}
 	}
-	err = json.Unmarshal(b, &obj)
+	dec := json.NewDecoder(bytes.NewReader(b))
+	dec.UseNumber()
+	err = dec.Decode(&obj)
 	if err != nil {
 		return nil, fmt.Errorf("failed to unmarshal schema json: %v", err)
 	}
@@ -109,8 +111,18 @@ type templateData struct {
 
 // -------------------- JSON to Markdown conversion --------------------
 // Copied from https://github.com/marcusolsson/json-schema-docs and slightly changed to fit the DocsJenny
+type constraints struct {
+	Pattern          string      `json:"pattern"`
+	Maximum          json.Number `json:"maximum"`
+	ExclusiveMinimum bool        `json:"exclusiveMinimum"`
+	Minimum          json.Number `json:"minimum"`
+	ExclusiveMaximum bool        `json:"exclusiveMaximum"`
+	MinLength        uint        `json:"minLength"`
+	MaxLength        uint        `json:"maxLength"`
+}
 
 type schema struct {
+	constraints
 	ID                   string             `json:"$id,omitempty"`
 	Ref                  string             `json:"$ref,omitempty"`
 	Schema               string             `json:"$schema,omitempty"`
@@ -480,7 +492,14 @@ func makeRows(s *schema) [][]string {
 	rows := make([][]string, 0, len(s.Properties))
 
 	for key, p := range s.Properties {
-		typeStr := propTypeStr(key, p)
+		alias := propTypeAlias(p)
+
+		var typeStr string
+		if alias != "" {
+			typeStr = alias
+		} else {
+			typeStr = propTypeStr(key, p)
+		}
 
 		// Emphasize required properties.
 		var required string
@@ -491,7 +510,6 @@ func makeRows(s *schema) [][]string {
 		}
 
 		var desc string
-
 		if p.inheritedFrom != "" {
 			desc = fmt.Sprintf("*(Inherited from [%s](#%s))*", p.inheritedFrom, strings.ToLower(p.inheritedFrom))
 		}
@@ -512,6 +530,10 @@ func makeRows(s *schema) [][]string {
 			desc += fmt.Sprintf(" Default: `%v`.", p.Default)
 		}
 
+		// Render a constraint only if it's not a type alias https://cuelang.org/docs/references/spec/#predeclared-identifiers
+		if alias == "" {
+			desc += constraintDescr(p)
+		}
 		rows = append(rows, []string{fmt.Sprintf("`%s`", key), typeStr, required, formatForTable(desc)})
 	}
 
@@ -528,6 +550,70 @@ func makeRows(s *schema) [][]string {
 	return rows
 }
 
+func propTypeAlias(prop *schema) string {
+	if prop.Minimum == "" || prop.Maximum == "" {
+		return ""
+	}
+
+	min := prop.Minimum
+	max := prop.Maximum
+
+	switch {
+	case min == "0" && max == "255":
+		return "uint8"
+	case min == "0" && max == "65535":
+		return "uint16"
+	case min == "0" && max == "4294967295":
+		return "uint32"
+	case min == "0" && max == "18446744073709551615":
+		return "uint64"
+	case min == "-128" && max == "127":
+		return "int8"
+	case min == "-32768" && max == "32767":
+		return "int16"
+	case min == "-2147483648" && max == "2147483647":
+		return "int32"
+	case min == "-9223372036854775808" && max == "9223372036854775807":
+		return "int64"
+	default:
+		return ""
+	}
+}
+
+func constraintDescr(prop *schema) string {
+	if prop.Minimum != "" && prop.Maximum != "" {
+		var left, right string
+		if prop.ExclusiveMinimum {
+			left = ">" + prop.Minimum.String()
+		} else {
+			left = ">=" + prop.Minimum.String()
+		}
+
+		if prop.ExclusiveMaximum {
+			right = "<" + prop.Maximum.String()
+		} else {
+			right = "<=" + prop.Maximum.String()
+		}
+		return fmt.Sprintf("\nConstraint: `%s & %s`.", left, right)
+	}
+
+	if prop.MinLength > 0 {
+		left := fmt.Sprintf(">=%v", prop.MinLength)
+		right := ""
+
+		if prop.MaxLength > 0 {
+			right = fmt.Sprintf(" && <=%v", prop.MaxLength)
+		}
+		return fmt.Sprintf("\nConstraint: `length %s`.", left+right)
+	}
+
+	if prop.Pattern != "" {
+		return fmt.Sprintf("\nConstraint: must match `%s`.", prop.Pattern)
+	}
+
+	return ""
+}
+
 func propTypeStr(propName string, propValue *schema) string {
 	// If the property has AdditionalProperties, it is most likely a map type
 	if propValue.AdditionalProperties != nil {