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Precompute reverse dependency graph for diff-mode change-impact analysis #147

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Merged
alxxjohn merged 1 commit into from
Aug 19, 2026
Merged

Precompute reverse dependency graph for diff-mode change-impact analysis #147

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7 changes: 4 additions & 3 deletions internal/codeguard/checks/design/design_change_impact.go
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Original file line number Diff line number Diff line change
Expand Up @@ -29,8 +29,9 @@ func changeImpactFindings(env support.Context, graphs []targetModuleGraph) []cor
entries := make([]core.ChangeImpactEntry, 0)
findings := make([]core.Finding, 0)
for _, item := range graphs {
reverse := item.graph.reverseDependencies()
for _, changed := range env.ChangedFiles {
entry, ok := changeImpactEntry(item, changed)
entry, ok := changeImpactEntry(item, reverse, changed)
if !ok {
continue
}
Expand All @@ -46,12 +47,12 @@ func changeImpactFindings(env support.Context, graphs []targetModuleGraph) []cor
return findings
}

func changeImpactEntry(item targetModuleGraph, changed string) (core.ChangeImpactEntry, bool) {
func changeImpactEntry(item targetModuleGraph, reverse map[string][]string, changed string) (core.ChangeImpactEntry, bool) {
module, ok := item.graph.fileToModule[filepath.ToSlash(changed)]
if !ok {
return core.ChangeImpactEntry{}, false
}
dependents := item.graph.transitiveDependents(module)
dependents := support.TransitiveDependents(reverse, module)
return core.ChangeImpactEntry{
Target: item.target.Name,
Language: item.graph.language,
Expand Down
15 changes: 6 additions & 9 deletions internal/codeguard/checks/design/design_dependency_graph.go
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Original file line number Diff line number Diff line change
@@ -1,10 +1,6 @@
package design

import (
"sort"

"github.com/devr-tools/codeguard/internal/codeguard/checks/support"
)
import "sort"

// moduleGraph is a language-neutral module import graph used for cycle,
// god-module, and change-impact analysis across languages.
Expand Down Expand Up @@ -118,14 +114,15 @@ func (g *moduleGraph) fanCounts() (map[string]int, map[string]int) {
return fanOut, fanIn
}

// transitiveDependents returns every module that reaches the given module
// through one or more import edges, sorted by name.
func (g *moduleGraph) transitiveDependents(module string) []string {
// reverseDependencies builds the reverse adjacency list shared by change-impact
// traversals. Callers should build it once after graph construction rather than
// rebuilding it for every changed module.
func (g *moduleGraph) reverseDependencies() map[string][]string {
reverse := make(map[string][]string, len(g.modules))
for from, node := range g.modules {
for _, edge := range node.edges {
reverse[edge.to] = append(reverse[edge.to], from)
}
}
return support.TransitiveDependents(reverse, module)
return reverse
}
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