Fix test logging output.

In version 1.0.0-1.6.0, our in-process non-binary test driver didn't
call go-plugin, and called log.SetOutput to control what got logged, to
avoid flooding test output with debug logs.

From version 1.6.0, the in-process non-binary test driver had the same
behavior, but we added an out-of-process binary test driver, which used
go-plugin, but had the provider in a separate process that sent its
stdout and stderr through Terraform. Terraform then, not the test
framework, was responsible for filtering the output.

With the introduction of our in-process binary test driver, however,
we're using go-plugin and Terraform isn't filtering log output for us.
In theory, the log.SetOutput call that was working for the in-process
non-binary test driver should've worked here, as well, and it sort of
did. The issue was that go-plugin calls log.SetOutput and sets it to
os.Stderr in plugin.Serve, which overrides our filter.

To get this behavior back, after every call to plugin.Serve, we override
the go-plugin log.SetOutput by calling our own again.

This also removes the helper/resource.logOutput function, replacing its
usage with helper/logging.SetOutput, which does the same thing. The only
difference should be that filtering on test name is no longer supported.
If we want to support that, we would need to plumb a testing.T through
to runProviderCommand, which involves updating a lot of code for
marginal gain; as far as I know, nobody actually uses the test name
filtering for logging, preferring instead to log everything and only run
the test they want logs for.

helper/resource/plugin.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 
 	"github.com/hashicorp/go-hclog"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/logging"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
 	grpcplugin "github.com/hashicorp/terraform-plugin-sdk/v2/internal/helper/plugin"
 	proto "github.com/hashicorp/terraform-plugin-sdk/v2/internal/tfplugin5"
@@ -57,6 +58,9 @@ func runProviderCommand(f func() error, wd *tftest.WorkingDir, opts *plugin.Serv
 		return err
 	}
 
+	// plugin.DebugServe hijacks our log output location, so let's reset it
+	logging.SetOutput()
+
 	reattachInfo := map[string]plugin.ReattachConfig{}
 	var namespaces []string
 	host := "registry.terraform.io"

helper/resource/testing.go

@@ -5,17 +5,13 @@ import (
 	"errors"
 	"flag"
 	"fmt"
-	"io"
-	"io/ioutil"
 	"log"
 	"os"
 	"regexp"
 	"strconv"
 	"strings"
-	"syscall"
 
 	"github.com/hashicorp/go-multierror"
-	"github.com/hashicorp/logutils"
 	tftest "github.com/hashicorp/terraform-plugin-test"
 	testing "github.com/mitchellh/go-testing-interface"
 
@@ -451,49 +447,6 @@ type TestStep struct {
 	providers map[string]*schema.Provider
 }
 
-// Set to a file mask in sprintf format where %s is test name
-const envLogPathMask = "TF_LOG_PATH_MASK"
-
-func logOutput(t testing.T) (logOutput io.Writer, err error) {
-	logOutput = ioutil.Discard
-
-	logLevel := logging.LogLevel()
-	if logLevel == "" {
-		return
-	}
-
-	logOutput = os.Stderr
-
-	if logPath := os.Getenv(logging.EnvLogFile); logPath != "" {
-		var err error
-		logOutput, err = os.OpenFile(logPath, syscall.O_CREAT|syscall.O_RDWR|syscall.O_APPEND, 0666)
-		if err != nil {
-			return nil, err
-		}
-	}
-
-	if logPathMask := os.Getenv(envLogPathMask); logPathMask != "" {
-		// Escape special characters which may appear if we have subtests
-		testName := strings.Replace(t.Name(), "/", "__", -1)
-
-		logPath := fmt.Sprintf(logPathMask, testName)
-		var err error
-		logOutput, err = os.OpenFile(logPath, syscall.O_CREAT|syscall.O_RDWR|syscall.O_APPEND, 0666)
-		if err != nil {
-			return nil, err
-		}
-	}
-
-	// This was the default since the beginning
-	logOutput = &logutils.LevelFilter{
-		Levels:   logging.ValidLevels,
-		MinLevel: logutils.LogLevel(logLevel),
-		Writer:   logOutput,
-	}
-
-	return
-}
-
 // ParallelTest performs an acceptance test on a resource, allowing concurrency
 // with other ParallelTest.
 //
@@ -526,11 +479,7 @@ func Test(t testing.T, c TestCase) {
 		return
 	}
 
-	logWriter, err := logOutput(t)
-	if err != nil {
-		t.Error(fmt.Errorf("error setting up logging: %s", err))
-	}
-	log.SetOutput(logWriter)
+	logging.SetOutput()
 
 	// get instances of all providers, so we can use the individual
 	// resources to shim the state during the tests.