buildifier: fix uninitialised check when using list unpack assignment (…

…#1202)

as the test added in this commit shows, prior to this commit, the
uninitialized check would incorrectly fail when using list unpack
assignment, if the same variable is reused later.

this modified CollectLValues, so that it supports list unpack
assignments (in addition to tuple, and normal assignments).

bzlenv/bzlenv.go

@@ -148,6 +148,10 @@ func CollectLValues(node build.Expr) []*build.Ident {
 		for _, item := range node.List {
 			result = append(result, CollectLValues(item)...)
 		}
+	case *build.ListExpr:
+		for _, item := range node.List {
+			result = append(result, CollectLValues(item)...)
+		}
 	}
 	return result
 }

warn/warn_control_flow_test.go

@@ -1281,6 +1281,15 @@ def foo():
 
   for x, y in z:
     bar(x)
+`,
+		[]string{},
+		scopeEverywhere)
+
+	checkFindings(t, "uninitialized", `
+def foo():
+  [x, y] = [1, 2]
+  x = 3
+  print(x)
 `,
 		[]string{},
 		scopeEverywhere)