Allow print calls in IR (open-policy-agent#5501)

Since this was unset on the compiler for -t plan, print
calls got erased from the plans. Since this is useful for
debugging plan execution, we should allow print in this
context. If undesired, this can still be disabled via
the capabilities feature.

Signed-off-by: Anders Eknert <[email protected]>

cmd/build.go

@@ -306,6 +306,10 @@ func dobuild(params buildParams, args []string) error {
 		compiler = compiler.WithBundleVerificationKeyID(params.pubKeyID)
 	}
 
+	if params.target.String() == compile.TargetPlan {
+		compiler = compiler.WithEnablePrintStatements(true)
+	}
+
 	err = compiler.Build(context.Background())
 	if err != nil {
 		return err

cmd/build_test.go

@@ -392,6 +392,73 @@ func TestBuildPlanWithPruneUnused(t *testing.T) {
 	})
 }
 
+func TestBuildPlanWithPrintStatements(t *testing.T) {
+
+	files := map[string]string{
+		"test.rego": `
+			package test
+
+			p { print("hello") }
+		`,
+	}
+
+	test.WithTempFS(files, func(root string) {
+		params := newBuildParams()
+		if err := params.target.Set("plan"); err != nil {
+			t.Fatal(err)
+		}
+		params.entrypoints.v = []string{"test"}
+		params.outputFile = path.Join(root, "bundle.tar.gz")
+
+		err := dobuild(params, []string{root})
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		_, err = loader.NewFileLoader().AsBundle(params.outputFile)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		f, err := os.Open(params.outputFile)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer f.Close()
+
+		gr, err := gzip.NewReader(f)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		tr := tar.NewReader(gr)
+		var found bool
+
+		for {
+			f, err := tr.Next()
+			if err == io.EOF {
+				break
+			} else if err != nil {
+				t.Fatal(err)
+			}
+			if f.Name == "/plan.json" {
+				found = true
+				plan, err := io.ReadAll(tr)
+				if err != nil {
+					t.Fatal(err)
+				}
+				if !strings.Contains(string(plan), "internal.print") {
+					t.Error("expected plan.json to contain reference to internal.print built-in function")
+				}
+			}
+		}
+
+		if !found {
+			t.Error("plan.json not found")
+		}
+	})
+}
+
 func TestBuildPlanWithRegoEntrypointAnnotations(t *testing.T) {
 
 	tests := []struct {