fix: only strip a literal "./" path prefix

.changeset/chilled-paths-keep-x.md

@@ -0,0 +1,10 @@
+---
+"changed-modules-go": patch
+"changed-roots": patch
+---
+
+fix: only strip a literal "./" prefix when normalizing paths
+
+The prefix-stripping regex had an unescaped dot, so it matched any single character followed
+by a slash. A module under a single-character top-level directory, such as `x/config`, was
+reported as `config`, and consumers received a module directory no directory holds.

actions/changed-modules-go/src/__tests__/path-ops.test.ts

@@ -110,6 +110,26 @@ describe("matchModule", () => {
       const result = matchModule("scripts/build.js", moduleDirectories);
       expect(result).toBe("scripts");
     });
+
+    // A single-character top-level directory used to be stripped along with the "./" prefix,
+    // so "x/config/go.mod" matched a module named "config" that no directory holds.
+    test("should keep a single-character top-level directory", () => {
+      const moduleDirectories = ["x/config"];
+      const result = matchModule("x/config/go.mod", moduleDirectories);
+      expect(result).toBe("x/config");
+    });
+
+    test('should still strip a leading "./" prefix', () => {
+      const moduleDirectories = ["x/config"];
+      const result = matchModule("./x/config/go.mod", moduleDirectories);
+      expect(result).toBe("x/config");
+    });
+
+    test('should normalize a module directory given with a "./" prefix', () => {
+      const moduleDirectories = ["./x/config"];
+      const result = matchModules(["x/config/go.mod"], moduleDirectories);
+      expect(result).toEqual([["x/config/go.mod", "x/config"]]);
+    });
   });
 });
 

actions/changed-modules-go/src/path-ops.ts

@@ -14,7 +14,7 @@ function normalizePath(p: string): string {
   if (s === "." || s === "./") return ".";
 
   // strip leading ./ and extra slashes
-  s = s.replace(/^.\//, "").replace(/\/+$/, "");
+  s = s.replace(/^\.\//, "").replace(/\/+$/, "");
   return s;
 }
 

actions/changed-roots/src/__tests__/path-ops.test.ts

@@ -110,6 +110,26 @@ describe("matchModule", () => {
       const result = matchModule("scripts/build.js", moduleDirectories);
       expect(result).toBe("scripts");
     });
+
+    // A single-character top-level directory used to be stripped along with the "./" prefix,
+    // so "x/config/go.mod" matched a module named "config" that no directory holds.
+    test("should keep a single-character top-level directory", () => {
+      const moduleDirectories = ["x/config"];
+      const result = matchModule("x/config/go.mod", moduleDirectories);
+      expect(result).toBe("x/config");
+    });
+
+    test('should still strip a leading "./" prefix', () => {
+      const moduleDirectories = ["x/config"];
+      const result = matchModule("./x/config/go.mod", moduleDirectories);
+      expect(result).toBe("x/config");
+    });
+
+    test('should normalize a module directory given with a "./" prefix', () => {
+      const moduleDirectories = ["./x/config"];
+      const result = matchModules(["x/config/go.mod"], moduleDirectories);
+      expect(result).toEqual([["x/config/go.mod", "x/config"]]);
+    });
   });
 });
 

actions/changed-roots/src/path-ops.ts

@@ -14,7 +14,7 @@ function normalizePath(p: string): string {
   if (s === "." || s === "./") return ".";
 
   // strip leading ./ and extra slashes
-  s = s.replace(/^.\//, "").replace(/\/+$/, "");
+  s = s.replace(/^\.\//, "").replace(/\/+$/, "");
   return s;
 }