Fix #237, fix #178: use go/packages

Use go/packages instead of x/tools/loader: it allows to work
with go modules and speedups loading of packages with the help
of build cache.

A lot of linters became "fast": they are enabled by --fast now and
work in 1-2 seconds. Only unparam, interfacer and megacheck
are "slow" linters now.

Average project is analyzed 20-40% faster than before if all linters are
enabled! If we enable all linters except unparam, interfacer and
megacheck analysis is 10-20x faster!

test/run_test.go

@@ -15,7 +15,7 @@ import (
 
 	"github.com/golangci/golangci-lint/pkg/exitcodes"
 	"github.com/golangci/golangci-lint/pkg/lint/lintersdb"
-	"github.com/stretchr/testify/assert"
+	assert "github.com/stretchr/testify/require"
 )
 
 var root = filepath.Join("..", "...")
@@ -36,8 +36,8 @@ func checkNoIssuesRun(t *testing.T, out string, exitCode int) {
 }
 
 func TestNoCongratsMessage(t *testing.T) {
-	out, exitCode := runGolangciLint(t, "../...")
-	assert.Equal(t, exitcodes.Success, exitCode)
+	out, exitCode := runGolangciLint(t, filepath.Join("..", "..."))
+	assert.Equal(t, exitcodes.Success, exitCode, out)
 	assert.Equal(t, "", out)
 }
 
@@ -51,26 +51,27 @@ func TestAutogeneratedNoIssues(t *testing.T) {
 	checkNoIssuesRun(t, out, exitCode)
 }
 
-func TestSymlinkLoop(t *testing.T) {
-	out, exitCode := runGolangciLint(t, filepath.Join(testdataDir, "symlink_loop", "..."))
-	checkNoIssuesRun(t, out, exitCode)
+func TestEmptyDirRun(t *testing.T) {
+	out, exitCode := runGolangciLint(t, filepath.Join(testdataDir, "nogofiles"))
+	assert.Equal(t, exitcodes.NoGoFiles, exitCode)
+	assert.Contains(t, out, ": no go files to analyze")
 }
 
-func TestRunOnAbsPath(t *testing.T) {
-	absPath, err := filepath.Abs(filepath.Join(testdataDir, ".."))
-	assert.NoError(t, err)
+func TestNotExistingDirRun(t *testing.T) {
+	out, exitCode := runGolangciLint(t, filepath.Join(testdataDir, "no_such_dir"))
+	assert.True(t, exitCode == exitcodes.WarningInTest || exitCode == exitcodes.IssuesFound)
+	assert.Contains(t, out, `cannot find package \"./testdata/no_such_dir\"`)
+}
 
-	out, exitCode := runGolangciLint(t, "--no-config", "--fast", absPath)
-	checkNoIssuesRun(t, out, exitCode)
-
-	out, exitCode = runGolangciLint(t, "--no-config", absPath)
+func TestSymlinkLoop(t *testing.T) {
+	out, exitCode := runGolangciLint(t, filepath.Join(testdataDir, "symlink_loop", "..."))
 	checkNoIssuesRun(t, out, exitCode)
 }
 
 func TestDeadline(t *testing.T) {
 	out, exitCode := runGolangciLint(t, "--deadline=1ms", root)
 	assert.Equal(t, exitcodes.Timeout, exitCode)
-	assert.Contains(t, out, "deadline exceeded: try increase it by passing --deadline option")
+	assert.Contains(t, strings.ToLower(out), "deadline exceeded: try increase it by passing --deadline option")
 }
 
 func runGolangciLint(t *testing.T, args ...string) (string, int) {
@@ -125,8 +126,9 @@ func runGolangciLintWithYamlConfigWithCode(t *testing.T, cfg string, args ...str
 }
 
 func TestTestsAreLintedByDefault(t *testing.T) {
-	out, exitCode := runGolangciLint(t, "./testdata/withtests")
-	assert.Equal(t, exitcodes.Success, exitCode, out)
+	out, exitCode := runGolangciLint(t, filepath.Join(testdataDir, "withtests"))
+	assert.Equal(t, exitcodes.IssuesFound, exitCode)
+	assert.Contains(t, out, "if block ends with a return")
 }
 
 func TestCgoOk(t *testing.T) {
@@ -134,11 +136,26 @@ func TestCgoOk(t *testing.T) {
 	checkNoIssuesRun(t, out, exitCode)
 }
 
+func TestCgoWithIssues(t *testing.T) {
+	out, exitCode := runGolangciLint(t, "--enable-all", filepath.Join(testdataDir, "cgo_with_issues"))
+	assert.Equal(t, exitcodes.IssuesFound, exitCode)
+	assert.Contains(t, out, "Printf format %t has arg cs of wrong type")
+}
+
 func TestUnsafeOk(t *testing.T) {
 	out, exitCode := runGolangciLint(t, "--enable-all", filepath.Join(testdataDir, "unsafe"))
 	checkNoIssuesRun(t, out, exitCode)
 }
 
+func TestSkippedDirs(t *testing.T) {
+	out, exitCode := runGolangciLint(t, "--print-issued-lines=false", "--no-config", "--skip-dirs", "skip_me", "-Egolint",
+		filepath.Join(testdataDir, "skipdirs", "..."))
+	assert.Equal(t, exitcodes.IssuesFound, exitCode)
+	assert.Equal(t, out,
+		"testdata/skipdirs/examples_no_skip/with_issue.go:8:9: if block ends with "+
+			"a return statement, so drop this else and outdent its block (golint)\n")
+}
+
 func TestDeadcodeNoFalsePositivesInMainPkg(t *testing.T) {
 	out, exitCode := runGolangciLint(t, "--no-config", "--disable-all", "-Edeadcode",
 		filepath.Join(testdataDir, "deadcode_main_pkg"))
@@ -173,7 +190,7 @@ func getEnabledByDefaultFastLintersExcept(except ...string) []string {
 	ebdl := m.GetAllEnabledByDefaultLinters()
 	ret := []string{}
 	for _, lc := range ebdl {
-		if lc.DoesFullImport {
+		if lc.NeedsSSARepr {
 			continue
 		}
 
@@ -189,7 +206,7 @@ func getAllFastLintersWith(with ...string) []string {
 	linters := lintersdb.NewManager().GetAllSupportedLinterConfigs()
 	ret := append([]string{}, with...)
 	for _, lc := range linters {
-		if lc.DoesFullImport {
+		if lc.NeedsSSARepr {
 			continue
 		}
 		ret = append(ret, lc.Name())
@@ -212,7 +229,7 @@ func getEnabledByDefaultFastLintersWith(with ...string) []string {
 	ebdl := lintersdb.NewManager().GetAllEnabledByDefaultLinters()
 	ret := append([]string{}, with...)
 	for _, lc := range ebdl {
-		if lc.DoesFullImport {
+		if lc.NeedsSSARepr {
 			continue
 		}
 
@@ -337,8 +354,8 @@ func TestEnabledLinters(t *testing.T) {
 		},
 		{
 			name:           "fast option combined with enable and enable-all",
-			args:           "--enable-all --fast --enable=typecheck",
-			el:             getAllFastLintersWith("typecheck"),
+			args:           "--enable-all --fast --enable=megacheck",
+			el:             getAllFastLintersWith("megacheck"),
 			noImplicitFast: true,
 		},
 	}
@@ -361,15 +378,6 @@ func TestEnabledLinters(t *testing.T) {
 	}
 }
 
-func TestGovetInFastMode(t *testing.T) {
-	cfg := `
-	linters-settings:
-		use-installed-packages: true
-	`
-	out := runGolangciLintWithYamlConfig(t, cfg, "--fast", "-Egovet", root)
-	assert.Equal(t, noIssuesOut, out)
-}
-
 func TestEnabledPresetsAreNotDuplicated(t *testing.T) {
 	out, _ := runGolangciLint(t, "--no-config", "-v", "-p", "style,bugs")
 	assert.Contains(t, out, "Active presets: [bugs style]")