gopackagesdriver: skip root packages that can't be built

go/tools/gopackagesdriver/gopackagesdriver_test.go

@@ -31,12 +31,19 @@ go_library(
 )
 
 go_test(
-	name = "hello_test",
-	srcs = [
-		"hello_test.go",
-		"hello_external_test.go",
-	],
-	embed = [":hello"],
+    name = "hello_test",
+    srcs = [
+        "hello_test.go",
+        "hello_external_test.go",
+    ],
+    embed = [":hello"],
+)
+
+go_library(
+    name = "incompatible",
+    srcs = ["incompatible.go"],
+    importpath = "example.com/incompatible",
+    target_compatible_with = ["@platforms//:incompatible"],
 )
 
 -- hello.go --
@@ -61,7 +68,11 @@ package hello_test
 import "testing"
 
 func TestHelloExternal(t *testing.T) {}
-		`,
+
+-- incompatible.go --
+//go:build ignore
+package hello
+`,
 	})
 }
 
@@ -167,6 +178,41 @@ func TestExternalTests(t *testing.T) {
 	}
 }
 
+// TestIncompatible checks that a target that can be queried but not analyzed
+// does not appear in .Roots.
+func TestIncompatible(t *testing.T) {
+	reader := strings.NewReader("{}")
+	out, _, err := bazel_testing.BazelOutputWithInput(reader, "run", "@io_bazel_rules_go//go/tools/gopackagesdriver", "--", "./...")
+	if err != nil {
+		t.Fatalf("error running bazel: %v", err)
+	}
+	var resp response
+	if err := json.Unmarshal(out, &resp); err != nil {
+		t.Fatalf("unmarshaling response: %v", err)
+	}
+
+	rootLabels := make(map[string]bool)
+	for _, root := range resp.Roots {
+		rootLabels[root] = true
+	}
+
+	// Verify //:hello is in .Roots and check whether its label starts with
+	// "@@" (bzlmod) or "@" (not bzlmod).
+	var incompatibleLabel string
+	if rootLabels["@@//:hello"] {
+		incompatibleLabel = "@@//:incompatible"
+	} else if rootLabels["@//:hello"] {
+		incompatibleLabel = "@//:incompatible"
+	} else {
+		t.Fatalf("response does not contain //:hello; roots were %s", strings.Join(resp.Roots, ", "))
+	}
+
+	// Verify //:incompatible is NOT in .Roots.
+	if rootLabels[incompatibleLabel] {
+		t.Fatalf("response contains root %s", incompatibleLabel)
+	}
+}
+
 func runForTest(t *testing.T, args ...string) driverResponse {
 	t.Helper()
 

go/tools/gopackagesdriver/packageregistry.go

@@ -115,12 +115,18 @@ func (pr *PackageRegistry) Match(labels []string) ([]string, []*FlatPackage) {
 					roots[pkg.ID] = struct{}{}
 				}
 			}
-		} else {
+		} else if _, ok := pr.packagesByID[label]; ok {
 			roots[label] = struct{}{}
 			// If an xtest package exists for this package add it to the roots
 			if _, ok := pr.packagesByID[label+"_xtest"]; ok {
 				roots[label+"_xtest"] = struct{}{}
 			}
+		} else {
+			// Skip a package if we don't have .pkg.json for it.
+			// This happens if 'bazel query' matches the target, but 'bazel build'
+			// can't analyze it, for example, if target_compatible_with is set
+			// with contraints not compatible with the host platform.
+			continue
 		}
 	}