add trace-query flag for rego

README.md

@@ -158,7 +158,7 @@ Conftest is also able to be used via Docker. Simply mount your configuration and
 and specify the relevant command like so:
 
 ```console
-$ docker run --rm -v (pwd):/project instrumenta/conftest test deployment.yaml
+$ docker run --rm -v $(pwd):/project instrumenta/conftest test deployment.yaml
 deployment.yaml
    Containers must not run as root in Deployment hello-kubernetes
 ```

acceptance.bats

@@ -32,6 +32,12 @@
   [ "$status" -eq 0 ]
 }
 
+@test "Has trace-query flag" {
+  run conftest test -p examples/kubernetes/policy examples/kubernetes/service.yaml --trace-query
+  [ "$status" -eq 0 ]
+  [[ "$output" =~ "Enter warn[msg] { data.kubernetes.is_service;" ]]
+}
+
 @test "Has help flag" {
   run conftest --help
   [ "$status" -eq 0 ]

conftest.go

@@ -21,6 +21,7 @@ import (
 	"github.com/logrusorgru/aurora"
 	"github.com/open-policy-agent/opa/ast"
 	"github.com/open-policy-agent/opa/rego"
+	"github.com/open-policy-agent/opa/topdown"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
@@ -183,16 +184,15 @@ func makeQuery(ctx context.Context, query string, input interface{}, compiler *a
 		return false
 	}
 
-	rego := rego.New(
-		rego.Query(query),
-		rego.Compiler(compiler),
-		rego.Input(input))
-
+	rego, stdout := buildRego(viper.GetBool("trace-query"), query, input, compiler)
 	rs, err := rego.Eval(ctx)
+
 	if err != nil {
 		return fmt.Errorf("Problem evaluating rego policy: %s", err)
 	}
 
+	topdown.PrettyTrace(os.Stdout, *stdout)
+
 	var errorsList *multierror.Error
 
 	for _, r := range rs {
@@ -209,6 +209,20 @@ func makeQuery(ctx context.Context, query string, input interface{}, compiler *a
 	return errorsList.ErrorOrNil()
 }
 
+func buildRego(trace bool, query string, input interface{}, compiler *ast.Compiler) (*rego.Rego, *topdown.BufferTracer) {
+	var regoObj *rego.Rego
+	var regoFunc []func(r *rego.Rego)
+	buf := topdown.NewBufferTracer()
+
+	regoFunc = append(regoFunc, rego.Query(query), rego.Compiler(compiler), rego.Input(input))
+	if trace {
+		regoFunc = append(regoFunc, rego.Tracer(buf))
+	}
+	regoObj = rego.New(regoFunc...)
+
+	return regoObj, buf
+}
+
 func buildCompiler(path string) (*ast.Compiler, error) {
 	files, err := ioutil.ReadDir(path)
 	if err != nil {
@@ -430,6 +444,7 @@ func init() {
 
 	RootCmd.PersistentFlags().StringP("policy", "p", "policy", "directory for Rego policy files")
 	RootCmd.PersistentFlags().BoolP("debug", "", false, "enable more verbose log output")
+	RootCmd.PersistentFlags().BoolP("trace-query", "", false, "enable more verbose trace output for rego queries")
 
 	testCmd.Flags().BoolP("fail-on-warn", "", false, "return a non-zero exit code if only warnings are found")
 	testCmd.Flags().BoolP("update", "", false, "update any policies before running the tests")
@@ -439,6 +454,7 @@ func init() {
 
 	viper.BindPFlag("policy", RootCmd.PersistentFlags().Lookup("policy"))
 	viper.BindPFlag("debug", RootCmd.PersistentFlags().Lookup("debug"))
+	viper.BindPFlag("trace-query", RootCmd.PersistentFlags().Lookup("trace-query"))
 
 	viper.BindPFlag("fail-on-warn", testCmd.Flags().Lookup("fail-on-warn"))
 	viper.BindPFlag("update", testCmd.Flags().Lookup("update"))

go.sum

@@ -241,6 +241,7 @@ github.com/logrusorgru/aurora v0.0.0-20190417130405-e50442bb4cb5 h1:1jmSMm6Ob8hs
 github.com/logrusorgru/aurora v0.0.0-20190417130405-e50442bb4cb5/go.mod h1:7rIyQOR62GCctdiQpZ/zOJlFyk6y+94wXzv6RNZgaR4=
 github.com/magiconair/properties v1.8.0 h1:LLgXmsheXeRoUOBOjtwPQCWIYqM/LU1ayDtDePerRcY=
 github.com/magiconair/properties v1.8.0/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=
+github.com/magiconair/properties v1.8.1 h1:ZC2Vc7/ZFkGmsVC9KvOjumD+G5lXy2RtTKyzRKO2BQ4=
 github.com/magiconair/properties v1.8.1/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=
 github.com/mailru/easyjson v0.0.0-20160728113105-d5b7844b561a/go.mod h1:C1wdFJiN94OJF2b5HbByQZoLdCWB1Yqtg26g4irojpc=
 github.com/mailru/easyjson v0.0.0-20180823135443-60711f1a8329/go.mod h1:C1wdFJiN94OJF2b5HbByQZoLdCWB1Yqtg26g4irojpc=
@@ -286,6 +287,7 @@ github.com/pelletier/go-toml v1.2.0 h1:T5zMGML61Wp+FlcbWjRDT7yAxhJNAiPPLOFECq181
 github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=
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 github.com/pelletier/go-toml v1.3.0/go.mod h1:PN7xzY2wHTK0K9p34ErDQMlFxa51Fk0OUruD3k1mMwo=
+github.com/pelletier/go-toml v1.4.0 h1:u3Z1r+oOXJIkxqw34zVhyPgjBsm6X2wn21NWs/HfSeg=
 github.com/pelletier/go-toml v1.4.0/go.mod h1:PN7xzY2wHTK0K9p34ErDQMlFxa51Fk0OUruD3k1mMwo=
 github.com/peterbourgon/diskv v2.0.1+incompatible h1:UBdAOUP5p4RWqPBg048CAvpKN+vxiaj6gdUUzhl4XmI=
 github.com/peterbourgon/diskv v2.0.1+incompatible/go.mod h1:uqqh8zWWbv1HBMNONnaR/tNboyR3/BZd58JJSHlUSCU=
@@ -301,6 +303,7 @@ github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZN
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+github.com/prometheus/client_golang v0.9.3 h1:9iH4JKXLzFbOAdtqv/a+j8aewx2Y8lAjAydhbaScPF8=
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@@ -312,13 +315,15 @@ github.com/prometheus/common v0.0.0-20181126121408-4724e9255275/go.mod h1:daVV7q
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+github.com/prometheus/common v0.4.1 h1:K0MGApIoQvMw27RTdJkPbr3JZ7DNbtxQNyi5STVM6Kw=
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+github.com/prometheus/procfs v0.0.0-20190523193104-a7aeb8df3389 h1:F/k2nob1S9M6v5Xkq7KjSTQirOYaYQord0jR4TwyVmY=
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@@ -333,6 +338,7 @@ github.com/sirupsen/logrus v1.2.0/go.mod h1:LxeOpSwHxABJmUn/MG1IvRgCAasNZTLOkJPx
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+github.com/sirupsen/logrus v1.4.2 h1:SPIRibHv4MatM3XXNO2BJeFLZwZ2LvZgfQ5+UNI2im4=
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@@ -356,6 +362,7 @@ github.com/spf13/pflag v1.0.3 h1:zPAT6CGy6wXeQ7NtTnaTerfKOsV6V6F8agHXFiazDkg=
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@@ -499,12 +506,14 @@ google.golang.org/genproto v0.0.0-20190128161407-8ac453e89fca/go.mod h1:L3J43x8/
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