From d46a5896b796f423d3b3df463f4b5a3ca5a98afe Mon Sep 17 00:00:00 2001
From: Will Dixon <dixonwille@hotmail.com>
Date: Thu, 31 May 2018 01:24:46 -0400
Subject: [PATCH] Add Depguard to supported linters

---
 .golangci.example.yml                         |   5 +
 Gopkg.lock                                    |   8 +-
 Gopkg.toml                                    |   4 +
 README.md                                     |   5 +-
 pkg/commands/run.go                           |  12 +
 pkg/config/config.go                          |   5 +
 pkg/enabled_linters.go                        |   1 +
 pkg/enabled_linters_test.go                   |   2 +
 pkg/golinters/depguard.go                     |  57 ++
 pkg/testdata/with_issues/depguard.go          |   9 +
 pkg/testdata/with_issues/gas.go               |   2 +-
 pkg/testdata/with_issues/unconvert.go         |   2 +-
 .../OpenPeeDeeP/depguard/.gitignore           |  12 +
 .../OpenPeeDeeP/depguard/Gopkg.lock           |  28 +
 .../OpenPeeDeeP/depguard/Gopkg.toml           |  39 +
 .../github.com/OpenPeeDeeP/depguard/LICENSE   | 674 ++++++++++++++++++
 .../github.com/OpenPeeDeeP/depguard/README.md |  71 ++
 .../OpenPeeDeeP/depguard/depguard.go          | 154 ++++
 18 files changed, 1086 insertions(+), 4 deletions(-)
 create mode 100644 pkg/golinters/depguard.go
 create mode 100644 pkg/testdata/with_issues/depguard.go
 create mode 100644 vendor/github.com/OpenPeeDeeP/depguard/.gitignore
 create mode 100644 vendor/github.com/OpenPeeDeeP/depguard/Gopkg.lock
 create mode 100644 vendor/github.com/OpenPeeDeeP/depguard/Gopkg.toml
 create mode 100644 vendor/github.com/OpenPeeDeeP/depguard/LICENSE
 create mode 100644 vendor/github.com/OpenPeeDeeP/depguard/README.md
 create mode 100644 vendor/github.com/OpenPeeDeeP/depguard/depguard.go

diff --git a/.golangci.example.yml b/.golangci.example.yml
index 251d0113..b0b99f79 100644
--- a/.golangci.example.yml
+++ b/.golangci.example.yml
@@ -31,6 +31,11 @@ linters-settings:
   goconst:
     min-len: 3
     min-occurrences: 3
+  depguard:
+    list-type: blacklist
+    include-go-root: false
+    packages:
+      - github.com/davecgh/go-spew/spew
 
 linters:
   enable:
diff --git a/Gopkg.lock b/Gopkg.lock
index 0d484792..556c6f14 100644
--- a/Gopkg.lock
+++ b/Gopkg.lock
@@ -11,6 +11,12 @@
   revision = "a9de4d6c1589158e002cc336c495bf11fbf3ea06"
   source = "github.com/golangci/gas"
 
+[[projects]]
+  branch = "master"
+  name = "github.com/OpenPeeDeeP/depguard"
+  packages = ["."]
+  revision = "f2dff4f73566d1b9bd73f9bfd765030fbae5263a"
+
 [[projects]]
   name = "github.com/StackExchange/wmi"
   packages = ["."]
@@ -410,6 +416,6 @@
 [solve-meta]
   analyzer-name = "dep"
   analyzer-version = 1
-  inputs-digest = "8cfc9eb6d890be05e9a019a4537c3fba5bcaf25a396437d0a8b402f6cc244d2e"
+  inputs-digest = "832e18c919daf77730cda91687bfd2d0b0b70fe6283c38b33e48ed89c2fd2def"
   solver-name = "gps-cdcl"
   solver-version = 1
diff --git a/Gopkg.toml b/Gopkg.toml
index 4ca2cf7b..4c41aac1 100644
--- a/Gopkg.toml
+++ b/Gopkg.toml
@@ -112,3 +112,7 @@
 [[override]]
   branch = "master"
   name = "github.com/golangci/lint"
+
+[[constraint]]
+  branch = "master"
+  name = "github.com/OpenPeeDeeP/depguard"
diff --git a/README.md b/README.md
index 2031f317..c0367b67 100644
--- a/README.md
+++ b/README.md
@@ -104,6 +104,7 @@ gofmt: Gofmt checks whether code was gofmt-ed. By default this tool runs with -s
 goimports: Goimports does everything that gofmt does. Additionally it checks unused imports
 maligned: Tool to detect Go structs that would take less memory if their fields were sorted
 megacheck: 3 sub-linters in one: unused, gosimple and staticcheck
+depguard: Go linter that checks if package imports are in a list of acceptable packages
 ```
 
 Pass `-E/--enable` to enable linter and `-D/--disable` to disable:
@@ -196,6 +197,7 @@ golangci-lint linters
 - [goimports](https://godoc.org/golang.org/x/tools/cmd/goimports): Goimports does everything that gofmt does. Additionally it checks unused imports
 - [maligned](https://github.com/mdempsky/maligned): Tool to detect Go structs that would take less memory if their fields were sorted
 - [megacheck](https://github.com/dominikh/go-tools/tree/master/cmd/megacheck): 3 sub-linters in one: unused, gosimple and staticcheck
+- [depguard](https://github.com/OpenPeeDeeP/depguard): Go linter that checks if package imports are in a list of acceptable packages
 
 # Configuration
 ## Command-Line Options
@@ -231,7 +233,7 @@ Linters presets:
 bugs: govet, errcheck, staticcheck, gas, megacheck
 unused: unused, structcheck, varcheck, ineffassign, deadcode, megacheck
 format: gofmt, goimports
-style: golint, gosimple, interfacer, unconvert, dupl, goconst, megacheck
+style: golint, gosimple, interfacer, unconvert, dupl, goconst, megacheck, depguard
 complexity: gocyclo
 performance: maligned
 ```
@@ -427,6 +429,7 @@ Thanks to developers and authors of used linters:
 - [golang/x/tools/goimports](https://godoc.org/golang.org/x/tools/cmd/goimports)
 - [mdempsky/maligned](https://github.com/mdempsky/maligned)
 - [dominikh/go-tools/megacheck](https://github.com/dominikh/go-tools/tree/master/cmd/megacheck)
+- [OpenPeeDeeP/depguard](https://github.com/OpenPeeDeeP/depguard)
 
 # Future Plans
 1. Upstream all changes of forked linters.
diff --git a/pkg/commands/run.go b/pkg/commands/run.go
index a2a9c177..eb9fc6df 100644
--- a/pkg/commands/run.go
+++ b/pkg/commands/run.go
@@ -88,6 +88,18 @@ func (e *Executor) initRun() {
 	runCmd.Flags().IntVar(&lsc.Goconst.MinOccurrencesCount, "goconst.min-occurrences",
 		3, "Goconst: minimum occurrences of constant string count to trigger issue")
 
+	// (@dixonwille) These flag is only used for testing purposes.
+	runCmd.Flags().StringSliceVar(&lsc.Depguard.Packages, "depguard.packages", nil,
+		"Depguard: packages to add to the list")
+	if err := runCmd.Flags().MarkHidden("depguard.packages"); err != nil {
+		panic(err) //Considering The only time this is called is if name does not exist
+	}
+	runCmd.Flags().BoolVar(&lsc.Depguard.IncludeGoRoot, "depguard.include-go-root", false,
+		"Depguard: check list against standard lib")
+	if err := runCmd.Flags().MarkHidden("depguard.include-go-root"); err != nil {
+		panic(err) //Considering The only time this is called is if name does not exist
+	}
+
 	// Linters config
 	lc := &e.cfg.Linters
 	runCmd.Flags().StringSliceVarP(&lc.Enable, "enable", "E", []string{}, "Enable specific linter")
diff --git a/pkg/config/config.go b/pkg/config/config.go
index 3ae69dd9..4de22e5c 100644
--- a/pkg/config/config.go
+++ b/pkg/config/config.go
@@ -91,6 +91,11 @@ type LintersSettings struct {
 		MinStringLen        int `mapstructure:"min-len"`
 		MinOccurrencesCount int `mapstructure:"min-occurrences"`
 	}
+	Depguard struct {
+		ListType      string `mapstructure:"list-type"`
+		Packages      []string
+		IncludeGoRoot bool `mapstructure:"inlude-go-root"`
+	}
 }
 
 type Linters struct {
diff --git a/pkg/enabled_linters.go b/pkg/enabled_linters.go
index ddb016b5..ce3c9f02 100644
--- a/pkg/enabled_linters.go
+++ b/pkg/enabled_linters.go
@@ -125,6 +125,7 @@ func GetAllSupportedLinterConfigs() []LinterConfig {
 		newLinterConfig(golinters.Maligned{}).WithFullImport().WithPresets(PresetPerformance).WithSpeed(10),
 		newLinterConfig(golinters.Megacheck{GosimpleEnabled: true, UnusedEnabled: true, StaticcheckEnabled: true}).
 			WithSSA().WithPresets(PresetStyle, PresetBugs, PresetUnused).WithSpeed(1),
+		newLinterConfig(golinters.Depguard{}).WithFullImport().WithPresets(PresetStyle).WithSpeed(6),
 	}
 
 	if os.Getenv("GOLANGCI_COM_RUN") == "1" {
diff --git a/pkg/enabled_linters_test.go b/pkg/enabled_linters_test.go
index 2d026d46..9bd197b3 100644
--- a/pkg/enabled_linters_test.go
+++ b/pkg/enabled_linters_test.go
@@ -100,6 +100,8 @@ func testOneSource(t *testing.T, sourcePath string) {
 		"--out-format=line-number",
 		"--print-welcome=false",
 		"--govet.check-shadowing=true",
+		"--depguard.include-go-root",
+		"--depguard.packages='log'",
 		sourcePath)
 	runGoErrchk(cmd, t)
 }
diff --git a/pkg/golinters/depguard.go b/pkg/golinters/depguard.go
new file mode 100644
index 00000000..8bef16a2
--- /dev/null
+++ b/pkg/golinters/depguard.go
@@ -0,0 +1,57 @@
+package golinters
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	depguardAPI "github.com/OpenPeeDeeP/depguard"
+	"github.com/golangci/golangci-lint/pkg/result"
+)
+
+type Depguard struct{}
+
+func (Depguard) Name() string {
+	return "depguard"
+}
+
+func (Depguard) Desc() string {
+	return "Go linter that checks if package imports are in a list of acceptable packages"
+}
+
+func (d Depguard) Run(ctx context.Context, lintCtx *Context) ([]result.Issue, error) {
+	dg := &depguardAPI.Depguard{
+		Packages:      lintCtx.Settings().Depguard.Packages,
+		IncludeGoRoot: lintCtx.Settings().Depguard.IncludeGoRoot,
+	}
+	listType := lintCtx.Settings().Depguard.ListType
+	var found bool
+	dg.ListType, found = depguardAPI.StringToListType[strings.ToLower(listType)]
+	if !found {
+		if listType != "" {
+			return nil, fmt.Errorf("unsure what list type %s is", listType)
+		}
+		dg.ListType = depguardAPI.LTBlacklist
+	}
+
+	issues, err := dg.Run(lintCtx.LoaderConfig, lintCtx.Program)
+	if err != nil {
+		return nil, err
+	}
+	if len(issues) == 0 {
+		return nil, nil
+	}
+	msgSuffix := "is in the blacklist"
+	if dg.ListType == depguardAPI.LTWhitelist {
+		msgSuffix = "is not in the whitelist"
+	}
+	res := make([]result.Issue, 0, len(issues))
+	for _, i := range issues {
+		res = append(res, result.Issue{
+			Pos:        i.Position,
+			Text:       fmt.Sprintf("%s %s", formatCode(i.PackageName, lintCtx.Cfg), msgSuffix),
+			FromLinter: d.Name(),
+		})
+	}
+	return res, nil
+}
diff --git a/pkg/testdata/with_issues/depguard.go b/pkg/testdata/with_issues/depguard.go
new file mode 100644
index 00000000..9ed1640a
--- /dev/null
+++ b/pkg/testdata/with_issues/depguard.go
@@ -0,0 +1,9 @@
+package testdata
+
+import (
+	"log" // ERROR "`log` is in the blacklist"
+)
+
+func SpewDebugInfo() {
+	log.Println("Debug info")
+}
diff --git a/pkg/testdata/with_issues/gas.go b/pkg/testdata/with_issues/gas.go
index 286164f3..6ba96de3 100644
--- a/pkg/testdata/with_issues/gas.go
+++ b/pkg/testdata/with_issues/gas.go
@@ -2,7 +2,7 @@ package testdata
 
 import (
 	"crypto/md5" // ERROR "G501: Blacklisted import crypto/md5: weak cryptographic primitive"
-	"log"
+	"log"        // nolint:depguard
 )
 
 func Gas() {
diff --git a/pkg/testdata/with_issues/unconvert.go b/pkg/testdata/with_issues/unconvert.go
index 85e4fb41..97399673 100644
--- a/pkg/testdata/with_issues/unconvert.go
+++ b/pkg/testdata/with_issues/unconvert.go
@@ -1,6 +1,6 @@
 package testdata
 
-import "log"
+import "log" // nolint:depguard
 
 func Unconvert() {
 	a := 1
diff --git a/vendor/github.com/OpenPeeDeeP/depguard/.gitignore b/vendor/github.com/OpenPeeDeeP/depguard/.gitignore
new file mode 100644
index 00000000..f1c181ec
--- /dev/null
+++ b/vendor/github.com/OpenPeeDeeP/depguard/.gitignore
@@ -0,0 +1,12 @@
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, build with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
diff --git a/vendor/github.com/OpenPeeDeeP/depguard/Gopkg.lock b/vendor/github.com/OpenPeeDeeP/depguard/Gopkg.lock
new file mode 100644
index 00000000..4fcbbe11
--- /dev/null
+++ b/vendor/github.com/OpenPeeDeeP/depguard/Gopkg.lock
@@ -0,0 +1,28 @@
+# This file is autogenerated, do not edit; changes may be undone by the next 'dep ensure'.
+
+
+[[projects]]
+  name = "github.com/kisielk/gotool"
+  packages = [
+    ".",
+    "internal/load"
+  ]
+  revision = "80517062f582ea3340cd4baf70e86d539ae7d84d"
+  version = "v1.0.0"
+
+[[projects]]
+  branch = "master"
+  name = "golang.org/x/tools"
+  packages = [
+    "go/ast/astutil",
+    "go/buildutil",
+    "go/loader"
+  ]
+  revision = "a5b4c53f6e8bdcafa95a94671bf2d1203365858b"
+
+[solve-meta]
+  analyzer-name = "dep"
+  analyzer-version = 1
+  inputs-digest = "d82a46da1f8e74876d14c0aa629966b2d180652e4cb74607a74cfd2bd9574905"
+  solver-name = "gps-cdcl"
+  solver-version = 1
diff --git a/vendor/github.com/OpenPeeDeeP/depguard/Gopkg.toml b/vendor/github.com/OpenPeeDeeP/depguard/Gopkg.toml
new file mode 100644
index 00000000..ba576822
--- /dev/null
+++ b/vendor/github.com/OpenPeeDeeP/depguard/Gopkg.toml
@@ -0,0 +1,39 @@
+# Gopkg.toml example
+#
+# Refer to https://golang.github.io/dep/docs/Gopkg.toml.html
+# for detailed Gopkg.toml documentation.
+#
+# required = ["github.com/user/thing/cmd/thing"]
+# ignored = ["github.com/user/project/pkgX", "bitbucket.org/user/project/pkgA/pkgY"]
+#
+# [[constraint]]
+#   name = "github.com/user/project"
+#   version = "1.0.0"
+#
+# [[constraint]]
+#   name = "github.com/user/project2"
+#   branch = "dev"
+#   source = "github.com/myfork/project2"
+#
+# [[override]]
+#   name = "github.com/x/y"
+#   version = "2.4.0"
+#
+# [prune]
+#   non-go = false
+#   go-tests = true
+#   unused-packages = true
+
+ignored = ["github.com/davecgh/go-spew/spew"]
+
+[prune]
+  go-tests = true
+  unused-packages = true
+
+[[constraint]]
+  name = "github.com/kisielk/gotool"
+  version = "1.0.0"
+
+[[constraint]]
+  branch = "master"
+  name = "golang.org/x/tools"
diff --git a/vendor/github.com/OpenPeeDeeP/depguard/LICENSE b/vendor/github.com/OpenPeeDeeP/depguard/LICENSE
new file mode 100644
index 00000000..94a9ed02
--- /dev/null
+++ b/vendor/github.com/OpenPeeDeeP/depguard/LICENSE
@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
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+software and other kinds of works.
+
+  The licenses for most software and other practical works are designed
+to take away your freedom to share and change the works.  By contrast,
+the GNU General Public License is intended to guarantee your freedom to
+share and change all versions of a program--to make sure it remains free
+software for all its users.  We, the Free Software Foundation, use the
+GNU General Public License for most of our software; it applies also to
+any other work released this way by its authors.  You can apply it to
+your programs, too.
+
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+
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+
+  "This License" refers to version 3 of the GNU General Public License.
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+  In the following three paragraphs, a "patent license" is any express
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+license to downstream recipients.  "Knowingly relying" means you have
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+  A patent license is "discriminatory" if it does not include within
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+or that patent license was granted, prior to 28 March 2007.
+
+  Nothing in this License shall be construed as excluding or limiting
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+otherwise be available to you under applicable patent law.
+
+  12. No Surrender of Others' Freedom.
+
+  If conditions are imposed on you (whether by court order, agreement or
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+the Program, the only way you could satisfy both those terms and this
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+
+  13. Use with the GNU Affero General Public License.
+
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+
+  14. Revised Versions of this License.
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+  The Free Software Foundation may publish revised and/or new versions of
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+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
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+Program specifies that a certain numbered version of the GNU General
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+
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+
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+
+  15. Disclaimer of Warranty.
+
+  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
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+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
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+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
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+
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+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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+
+    You should have received a copy of the GNU General Public License
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+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<http://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<http://www.gnu.org/philosophy/why-not-lgpl.html>.
diff --git a/vendor/github.com/OpenPeeDeeP/depguard/README.md b/vendor/github.com/OpenPeeDeeP/depguard/README.md
new file mode 100644
index 00000000..5cf22a29
--- /dev/null
+++ b/vendor/github.com/OpenPeeDeeP/depguard/README.md
@@ -0,0 +1,71 @@
+# Depguard
+
+Go linter that checks package imports are in a list of acceptable packages. It
+supports a white list and black list option and only checks the prefixes of the
+import path. This allows you to allow imports from a whole organization or only
+allow specific packages within a repository.
+
+## Install
+
+```bash
+go get -u github.com/OpenPeeDeeP/depguard
+```
+
+## Config
+
+By default, Depguard looks for a file named `.depguard.json` in the current
+current working directory. If it is somewhere else, pass in the `-c` flag with
+the location of your configuration file.
+
+The following is an example configuration file.
+
+```json
+{
+  "type": "whitelist",
+  "packages": [
+    "github.com/OpenPeeDeeP/depguard"
+  ],
+  "includeGoRoot": true
+}
+```
+
+- `type` can be either `whitelist` or `blacklist`. This check is case insensitive.
+If not specified the default is `blacklist`.
+- `packages` is a list of packages for the list type specified.
+- Set `includeGoRoot` to true if you want to check the list against standard lib.
+If not specified the default is false.
+
+## Gometalinter
+
+The binary installation of this linter can be used with
+[Gometalinter](github.com/alecthomas/gometalinter).
+
+If you use a configuration file for Gometalinter then the following will need to
+be added to your configuration file.
+
+```json
+{
+  "linters": {
+    "depguard": {
+      "command": "depguard -c path/to/config.json",
+      "pattern": "PATH:LINE:COL:MESSAGE",
+      "installFrom": "github.com/OpenPeeDeeP/depguard",
+      "isFast": true,
+      "partitionStrategy": "packages"
+    }
+  }
+}
+```
+
+If you prefer the command line way the following will work for you as well.
+
+```bash
+gometalinter --linter='depguard:depguard -c path/to/config.json:PATH:LINE:COL:MESSAGE'
+```
+
+## Golangci-lint
+
+This linter was built with
+[Golangci-lint](https://github.com/golangci/golangci-lint) in mind. I have opened
+up a [Pull Request](github.com/golangci/golangci-lint/pull/47) into GolangCI-Lint
+and will hopefully get that merged in soon.
diff --git a/vendor/github.com/OpenPeeDeeP/depguard/depguard.go b/vendor/github.com/OpenPeeDeeP/depguard/depguard.go
new file mode 100644
index 00000000..5e6464e9
--- /dev/null
+++ b/vendor/github.com/OpenPeeDeeP/depguard/depguard.go
@@ -0,0 +1,154 @@
+package depguard
+
+import (
+	"go/build"
+	"go/token"
+	"os"
+	"sort"
+	"strings"
+
+	"golang.org/x/tools/go/loader"
+)
+
+//ListType states what kind of list is passed in.
+type ListType int
+
+const (
+	//LTBlacklist states the list given is a blacklist. (default)
+	LTBlacklist ListType = iota
+	//LTWhitelist states the list given is a whitelist.
+	LTWhitelist
+)
+
+//StringToListType makes it easier to turn a string into a ListType.
+//It assumes that the string representation is lower case.
+var StringToListType = map[string]ListType{
+	"whitelist": LTWhitelist,
+	"blacklist": LTBlacklist,
+}
+
+//Issue with the package with PackageName at the Position.
+type Issue struct {
+	PackageName string
+	Position    token.Position
+}
+
+//Depguard checks imports to make sure they follow the given list and constraints.
+type Depguard struct {
+	ListType      ListType
+	Packages      []string
+	IncludeGoRoot bool
+	buildCtx      *build.Context
+	cwd           string
+}
+
+//Run checks for dependencies given the program and validates them against
+//Packages.
+func (dg *Depguard) Run(config *loader.Config, prog *loader.Program) ([]*Issue, error) {
+	//Shortcut execution on an empty blacklist as that means every package is allowed
+	if dg.ListType == LTBlacklist && len(dg.Packages) == 0 {
+		return nil, nil
+	}
+
+	if err := dg.initialize(config, prog); err != nil {
+		return nil, err
+	}
+
+	directImports, err := dg.createImportMap(prog)
+	if err != nil {
+		return nil, err
+	}
+	var issues []*Issue
+	for pkg, positions := range directImports {
+		if dg.flagIt(pkg) {
+			for _, pos := range positions {
+				issues = append(issues, &Issue{
+					PackageName: pkg,
+					Position:    pos,
+				})
+			}
+		}
+	}
+	return issues, nil
+}
+
+func (dg *Depguard) initialize(config *loader.Config, prog *loader.Program) error {
+	//Try and get the current working directory
+	dg.cwd = config.Cwd
+	if dg.cwd == "" {
+		var err error
+		dg.cwd, err = os.Getwd()
+		if err != nil {
+			return err
+		}
+	}
+
+	//Use the &build.Default if one is not specified
+	dg.buildCtx = config.Build
+	if dg.buildCtx == nil {
+		dg.buildCtx = &build.Default
+	}
+
+	//Sort the packages so we can have a faster search in the array
+	sort.Strings(dg.Packages)
+	return nil
+}
+
+func (dg *Depguard) createImportMap(prog *loader.Program) (map[string][]token.Position, error) {
+	importMap := make(map[string][]token.Position)
+	//For the directly imported packages
+	for _, imported := range prog.InitialPackages() {
+		//Go through their files
+		for _, file := range imported.Files {
+			//And populate a map of all direct imports and their positions
+			//This will filter out GoRoot depending on the Depguard.IncludeGoRoot
+			for _, fileImport := range file.Imports {
+				fileImportPath := cleanBasicLitString(fileImport.Path.Value)
+				if !dg.IncludeGoRoot {
+					pkg, err := dg.buildCtx.Import(fileImportPath, dg.cwd, 0)
+					if err != nil {
+						return nil, err
+					}
+					if pkg.Goroot {
+						continue
+					}
+				}
+				position := prog.Fset.Position(fileImport.Pos())
+				positions, found := importMap[fileImportPath]
+				if !found {
+					importMap[fileImportPath] = []token.Position{
+						position,
+					}
+					continue
+				}
+				importMap[fileImportPath] = append(positions, position)
+			}
+		}
+	}
+	return importMap, nil
+}
+
+func (dg *Depguard) pkgInList(pkg string) bool {
+	//Idx represents where in the package slice the passed in package would go
+	//when sorted. -1 Just means that it would be at the very front of the slice.
+	idx := sort.Search(len(dg.Packages), func(i int) bool {
+		return dg.Packages[i] > pkg
+	}) - 1
+	//This means that the package passed in has no way to be prefixed by anything
+	//in the package list as it is already smaller then everything
+	if idx == -1 {
+		return false
+	}
+	return strings.HasPrefix(pkg, dg.Packages[idx])
+}
+
+//InList | WhiteList | BlackList
+//   y   |           |     x
+//   n   |     x     |
+func (dg *Depguard) flagIt(pkg string) bool {
+	return dg.pkgInList(pkg) == (dg.ListType == LTBlacklist)
+}
+
+func cleanBasicLitString(value string) string {
+	return strings.Trim(value, "\"\\")
+}