fix(scanner): Resolve tsconfig alias targets written as "./*"

scanner/aliastarget_test.go

@@ -0,0 +1,83 @@
+package scanner
+
+import (
+	"context"
+	"reflect"
+	"sort"
+	"testing"
+)
+
+// create-next-app has shipped "@/*": ["./*"] for years, so this is the most
+// common TypeScript layout in the wild. The substituted target was "./lib/a1"
+// while the file index holds "lib/a1", so nothing matched and a file imported
+// everywhere reported no importers at all.
+func TestTsconfigDotSlashAliasResolvesImporters(t *testing.T) {
+	graph, err := BuildFileGraph(context.Background(), "../testdata/tsconfig-alias-dotslash", Filters{})
+	if err != nil {
+		t.Fatalf("build alias fixture graph: %v", err)
+	}
+	// Compare as a set: the graph appends importers in analysis order, which
+	// is not deterministic across runs (see the note in the PR for #173). The
+	// exactness this asserts is membership, not sequence.
+	got := append([]string(nil), graph.Importers["lib/a1.ts"]...)
+	sort.Strings(got)
+	want := []string{"app/layout.tsx", "app/page.tsx"}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("lib/a1.ts importers = %v, want exactly %v", got, want)
+	}
+}
+
+func TestNormalizeAliasTarget(t *testing.T) {
+	for _, tc := range []struct {
+		name   string
+		target string
+		want   string
+	}{
+		{"create-next-app default", "./lib/a1", "lib/a1"},
+		{"bare wildcard target", "lib/a1", "lib/a1"},
+		{"nested with dot slash", "./src/lib/s1", "src/lib/s1"},
+		{"redundant separators", "./src//lib/../lib/s1", "src/lib/s1"},
+		{"bare dot collapses to root", ".", ""},
+		{"dot slash only", "./", ""},
+		{"empty stays empty", "", ""},
+		// A target escaping the project must not be silently rewritten into a
+		// path that could match an unrelated file.
+		{"parent traversal preserved", "../shared/x", "../shared/x"},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := normalizeAliasTarget(tc.target); got != tc.want {
+				t.Fatalf("normalizeAliasTarget(%q) = %q, want %q", tc.target, got, tc.want)
+			}
+		})
+	}
+}
+
+// Every alias target shape has to keep resolving, so the "./" fix cannot
+// regress the forms that already worked.
+func TestPathAliasTargetShapes(t *testing.T) {
+	files := []FileInfo{{Path: "lib/a1.ts"}, {Path: "src/lib/s1.ts"}, {Path: "app/page.tsx"}}
+	idx := buildFileIndex(files, "")
+
+	for _, tc := range []struct {
+		name    string
+		imp     string
+		aliases map[string][]string
+		baseURL string
+		want    []string
+	}{
+		{"dot slash wildcard", "@/lib/a1", map[string][]string{"@/*": {"./*"}}, "", []string{"lib/a1.ts"}},
+		{"bare wildcard", "@/lib/a1", map[string][]string{"@/*": {"*"}}, "", []string{"lib/a1.ts"}},
+		{"nested dot slash", "@/lib/s1", map[string][]string{"@/*": {"./src/*"}}, "", []string{"src/lib/s1.ts"}},
+		{"nested bare", "@/lib/s1", map[string][]string{"@/*": {"src/*"}}, "", []string{"src/lib/s1.ts"}},
+		{"base url with dot slash", "@/lib/a1", map[string][]string{"@/*": {"./*"}}, ".", []string{"lib/a1.ts"}},
+		{"exact alias with dot slash", "@app", map[string][]string{"@app": {"./lib/a1"}}, "", []string{"lib/a1.ts"}},
+		{"unmatched alias resolves to nothing", "@/nope", map[string][]string{"@/*": {"./*"}}, "", nil},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			got := resolvePathAlias(tc.imp, tc.aliases, tc.baseURL, idx, "typescript")
+			if !reflect.DeepEqual(got, tc.want) {
+				t.Fatalf("resolvePathAlias(%q, %v, baseURL=%q) = %v, want %v", tc.imp, tc.aliases, tc.baseURL, got, tc.want)
+			}
+		})
+	}
+}

scanner/filegraph.go

@@ -811,6 +811,23 @@ func readTSConfig(configPath, root string) (map[string][]string, string) {
 	return paths, baseURL
 }
 
+// normalizeAliasTarget puts a substituted tsconfig alias target into the same
+// shape as the file index, which stores repository-relative paths with no "./"
+// prefix. create-next-app has shipped "@/*": ["./*"] for years, so the
+// substituted target is "./lib/a1" while the index holds "lib/a1" and nothing
+// matches. filepath.Join already cleaned the target when a baseUrl was set,
+// which is why this only ever bit projects without one.
+func normalizeAliasTarget(target string) string {
+	if target == "" {
+		return target
+	}
+	cleaned := filepath.ToSlash(filepath.Clean(target))
+	if cleaned == "." {
+		return ""
+	}
+	return cleaned
+}
+
 // resolvePathAlias attempts to resolve an import using TypeScript path aliases
 // e.g., "@modules/auth" with alias "@modules/*" -> ["src/modules/*"] becomes "src/modules/auth"
 func resolvePathAlias(imp string, pathAliases map[string][]string, baseURL string, idx *fileIndex, sourceLanguage string) []string {
@@ -828,6 +845,7 @@ func resolvePathAlias(imp string, pathAliases map[string][]string, baseURL strin
 					if baseURL != "" && !filepath.IsAbs(resolved) {
 						resolved = filepath.Join(baseURL, resolved)
 					}
+					resolved = normalizeAliasTarget(resolved)
 					if files := tryExactMatch(resolved, idx, sourceLanguage); len(files) > 0 {
 						return files
 					}
@@ -863,6 +881,8 @@ func resolvePathAlias(imp string, pathAliases map[string][]string, baseURL strin
 				resolved = filepath.Join(baseURL, resolved)
 			}
 
+			resolved = normalizeAliasTarget(resolved)
+
 			// Try to find matching files
 			if files := tryExactMatch(resolved, idx, sourceLanguage); len(files) > 0 {
 				return files

testdata/tsconfig-alias-dotslash/app/layout.tsx

@@ -0,0 +1,5 @@
+import { a1 } from "@/lib/a1";
+
+export function Layout() {
+  return a1();
+}

testdata/tsconfig-alias-dotslash/app/page.tsx

@@ -0,0 +1,5 @@
+import { a1 } from "@/lib/a1";
+
+export default function Page() {
+  return a1();
+}

testdata/tsconfig-alias-dotslash/lib/a1.ts

@@ -0,0 +1,3 @@
+export function a1(): string {
+  return "a1";
+}

testdata/tsconfig-alias-dotslash/tsconfig.json

@@ -0,0 +1,7 @@
+{
+  "compilerOptions": {
+    "paths": {
+      "@/*": ["./*"]
+    }
+  }
+}