Add deps subcommand

These changes add a new subcommand that analyzes policies and prints
base and virtual document dependencies.

Signed-off-by: Torin Sandall <torinsandall@gmail.com>

cmd/deps.go

@@ -0,0 +1,113 @@
+// Copyright 2018 The OPA Authors.  All rights reserved.
+// Use of this source code is governed by an Apache2
+// license that can be found in the LICENSE file.
+
+package cmd
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/open-policy-agent/opa/dependencies"
+	"github.com/open-policy-agent/opa/internal/presentation"
+
+	"github.com/open-policy-agent/opa/ast"
+	"github.com/open-policy-agent/opa/loader"
+	"github.com/open-policy-agent/opa/util"
+	"github.com/pkg/errors"
+	"github.com/spf13/cobra"
+)
+
+type depsCommandParams struct {
+	dataPaths repeatedStringFlag
+	format    *util.EnumFlag
+	ignore    []string
+}
+
+const (
+	depsFormatPretty = "pretty"
+	depsFormatJSON   = "json"
+)
+
+func init() {
+
+	var params depsCommandParams
+
+	params.format = util.NewEnumFlag(depsFormatPretty, []string{
+		depsFormatPretty, depsFormatJSON,
+	})
+
+	depsCommand := &cobra.Command{
+		Use:   "deps <query>",
+		Short: "Analyze Rego query dependencies",
+		PreRunE: func(cmd *cobra.Command, args []string) error {
+			if len(args) != 1 {
+				return errors.New("specify exactly one query argument")
+			}
+			return nil
+		},
+		Run: func(cmd *cobra.Command, args []string) {
+			if err := deps(args, params); err != nil {
+				fmt.Fprintln(os.Stderr, err)
+				os.Exit(1)
+			}
+		},
+	}
+
+	depsCommand.Flags().VarP(params.format, "format", "f", "set output format")
+	depsCommand.Flags().VarP(&params.dataPaths, "data", "d", "set data file(s) or directory path(s)")
+	setIgnore(depsCommand.Flags(), &params.ignore)
+
+	RootCommand.AddCommand(depsCommand)
+}
+
+func deps(args []string, params depsCommandParams) error {
+
+	query, err := ast.ParseBody(args[0])
+	if err != nil {
+		return err
+	}
+
+	f := loaderFilter{
+		Ignore: params.ignore,
+	}
+
+	result, err := loader.Filtered(params.dataPaths.v, f.Apply)
+	if err != nil {
+		return err
+	}
+
+	modules := map[string]*ast.Module{}
+	for _, m := range result.Modules {
+		modules[m.Name] = m.Parsed
+	}
+
+	compiler := ast.NewCompiler()
+	compiler.Compile(modules)
+
+	if compiler.Failed() {
+		return compiler.Errors
+	}
+
+	brs, err := dependencies.Base(compiler, query)
+	if err != nil {
+		return err
+	}
+
+	vrs, err := dependencies.Virtual(compiler, query)
+	if err != nil {
+		return err
+	}
+
+	output := presentation.DepAnalysisOutput{
+		Base:    brs,
+		Virtual: vrs,
+	}
+
+	switch params.format.String() {
+	case depsFormatJSON:
+		return presentation.JSON(os.Stdout, output)
+	default:
+		return output.Pretty(os.Stdout)
+	}
+}

internal/presentation/presentation.go

@@ -25,6 +25,81 @@ import (
 	"github.com/open-policy-agent/opa/topdown"
 )
 
+// DepAnalysisOutput contains the result of dependency analysis to be presented.
+type DepAnalysisOutput struct {
+	Base    []ast.Ref `json:"base,omitempty"`
+	Virtual []ast.Ref `json:"virtual,omitempty"`
+}
+
+// JSON outputs o to w as JSON.
+func (o DepAnalysisOutput) JSON(w io.Writer) error {
+	o.sort()
+	return JSON(w, o)
+}
+
+// Pretty outputs o to w in a human-readable format.
+func (o DepAnalysisOutput) Pretty(w io.Writer) error {
+
+	var headers []string
+	var rows [][]string
+
+	// Fill two columns if results have base and virtual docs. Else fill one column.
+	if len(o.Base) > 0 && len(o.Virtual) > 0 {
+		maxLen := len(o.Base)
+		if len(o.Virtual) > maxLen {
+			maxLen = len(o.Virtual)
+		}
+		headers = []string{"Base Documents", "Virtual Documents"}
+		rows = make([][]string, maxLen)
+		for i := range rows {
+			rows[i] = make([]string, 2)
+			if i < len(o.Base) {
+				rows[i][0] = o.Base[i].String()
+			}
+			if i < len(o.Virtual) {
+				rows[i][1] = o.Virtual[i].String()
+			}
+		}
+	} else if len(o.Base) > 0 {
+		headers = []string{"Base Documents"}
+		rows = make([][]string, len(o.Base))
+		for i := range rows {
+			rows[i] = []string{o.Base[i].String()}
+		}
+	} else if len(o.Virtual) > 0 {
+		headers = []string{"Virtual Documents"}
+		rows = make([][]string, len(o.Base))
+		for i := range rows {
+			rows[i] = []string{o.Virtual[i].String()}
+		}
+	}
+
+	if len(rows) == 0 {
+		return nil
+	}
+
+	table := tablewriter.NewWriter(w)
+	table.SetHeader(headers)
+	table.SetAutoWrapText(false)
+	for i := range rows {
+		table.Append(rows[i])
+	}
+
+	table.Render()
+
+	return nil
+}
+
+func (o DepAnalysisOutput) sort() {
+	sort.Slice(o.Base, func(i, j int) bool {
+		return o.Base[i].Compare(o.Base[j]) < 0
+	})
+
+	sort.Slice(o.Virtual, func(i, j int) bool {
+		return o.Virtual[i].Compare(o.Virtual[j]) < 0
+	})
+}
+
 // Output contains the result of evaluation to be presented.
 type Output struct {
 	Error       error                `json:"error,omitempty"`