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package analysis
import (
"fmt"
"reflect"
"strings"
"unicode"
)
// Validate reports an error if any of the analyzers are misconfigured.
// Checks include:
// that the name is a valid identifier;
// that the Requires graph is acyclic;
// that analyzer fact types are unique;
// that each fact type is a pointer.
func Validate(analyzers []*Analyzer) error {
// Map each fact type to its sole generating analyzer.
factTypes := make(map[reflect.Type]*Analyzer)
// Traverse the Requires graph, depth first.
const (
white = iota
grey
black
finished
)
color := make(map[*Analyzer]uint8)
var visit func(a *Analyzer) error
visit = func(a *Analyzer) error {
if a == nil {
return fmt.Errorf("nil *Analyzer")
}
if color[a] == white {
color[a] = grey
// names
if !validIdent(a.Name) {
return fmt.Errorf("invalid analyzer name %q", a)
}
if a.Doc == "" {
return fmt.Errorf("analyzer %q is undocumented", a)
}
// fact types
for _, f := range a.FactTypes {
if f == nil {
return fmt.Errorf("analyzer %s has nil FactType", a)
}
t := reflect.TypeOf(f)
if prev := factTypes[t]; prev != nil {
return fmt.Errorf("fact type %s registered by two analyzers: %v, %v",
t, a, prev)
}
if t.Kind() != reflect.Ptr {
return fmt.Errorf("%s: fact type %s is not a pointer", a, t)
}
factTypes[t] = a
}
// recursion
for _, req := range a.Requires {
if err := visit(req); err != nil {
return err
}
}
color[a] = black
}
if color[a] == grey {
stack := []*Analyzer{a}
inCycle := map[string]bool{}
for len(stack) > 0 {
current := stack[len(stack)-1]
stack = stack[:len(stack)-1]
if color[current] == grey && !inCycle[current.Name] {
inCycle[current.Name] = true
stack = append(stack, current.Requires...)
}
}
return &CycleInRequiresGraphError{AnalyzerNames: inCycle}
}
return nil
}
for _, a := range analyzers {
if err := visit(a); err != nil {
return err
}
}
// Reject duplicates among analyzers.
// Precondition: color[a] == black.
// Postcondition: color[a] == finished.
for _, a := range analyzers {
if color[a] == finished {
return fmt.Errorf("duplicate analyzer: %s", a.Name)
}
color[a] = finished
}
return nil
}
func validIdent(name string) bool {
for i, r := range name {
if !(r == '_' || unicode.IsLetter(r) || i > 0 && unicode.IsDigit(r)) {
return false
}
}
return name != ""
}
type CycleInRequiresGraphError struct {
AnalyzerNames map[string]bool
}
func (e *CycleInRequiresGraphError) Error() string {
var b strings.Builder
b.WriteString("cycle detected involving the following analyzers:")
for n := range e.AnalyzerNames {
b.WriteByte(' ')
b.WriteString(n)
}
return b.String()
}
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