Improve error messages, esp. when the server is running

* Add file context to minifier errors when publishing
* Misc fixes (see issues)
* Allow custom server error template in layouts/server/error.html

To get to this, this commit also cleans up and simplifies the code surrounding errors and files. This also removes the usage of `github.com/pkg/errors`, mostly because of https://github.com/pkg/errors/issues/223 -- but also because most of this is now built-in to Go.

Fixes #9852
Fixes #9857
Fixes #9863

8 files changed, 28 insertions, 41 deletions

diff --git a/resources/resource_transformers/babel/babel.go b/resources/resource_transformers/babel/babel.go
index a4744961e..9a9110f62 100644
--- a/resources/resource_transformers/babel/babel.go
+++ b/resources/resource_transformers/babel/babel.go
@@ -15,6 +15,7 @@ package babel
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"io/ioutil"
 	"os"
@@ -34,7 +35,6 @@ import (
 	"github.com/gohugoio/hugo/common/herrors"
 	"github.com/gohugoio/hugo/resources"
 	"github.com/gohugoio/hugo/resources/resource"
-	"github.com/pkg/errors"
 )
 
 // Options from https://babeljs.io/docs/en/options
@@ -141,7 +141,7 @@ func (t *babelTransformation) Transform(ctx *resources.ResourceTransformationCtx
 		configFile = t.rs.BaseFs.ResolveJSConfigFile(configFile)
 		if configFile == "" && t.options.Config != "" {
 			// Only fail if the user specified config file is not found.
-			return errors.Errorf("babel config %q not found:", configFile)
+			return fmt.Errorf("babel config %q not found:", configFile)
 		}
 	}
 
@@ -203,7 +203,7 @@ func (t *babelTransformation) Transform(ctx *resources.ResourceTransformationCtx
 		if hexec.IsNotFound(err) {
 			return herrors.ErrFeatureNotAvailable
 		}
-		return errors.Wrap(err, errBuf.String())
+		return fmt.Errorf(errBuf.String()+": %w", err)
 	}
 
 	content, err := ioutil.ReadAll(compileOutput)
diff --git a/resources/resource_transformers/integrity/integrity.go b/resources/resource_transformers/integrity/integrity.go
index bbd0b6675..e15754685 100644
--- a/resources/resource_transformers/integrity/integrity.go
+++ b/resources/resource_transformers/integrity/integrity.go
@@ -19,14 +19,13 @@ import (
 	"crypto/sha512"
 	"encoding/base64"
 	"encoding/hex"
+	"fmt"
 	"hash"
 	"html/template"
 	"io"
 
 	"github.com/gohugoio/hugo/resources/internal"
 
-	"github.com/pkg/errors"
-
 	"github.com/gohugoio/hugo/resources"
 	"github.com/gohugoio/hugo/resources/resource"
 )
@@ -92,7 +91,7 @@ func newHash(algo string) (hash.Hash, error) {
 	case "sha512":
 		return sha512.New(), nil
 	default:
-		return nil, errors.Errorf("unsupported crypto algo: %q, use either md5, sha256, sha384 or sha512", algo)
+		return nil, fmt.Errorf("unsupported crypto algo: %q, use either md5, sha256, sha384 or sha512", algo)
 	}
 }
 
diff --git a/resources/resource_transformers/js/build.go b/resources/resource_transformers/js/build.go
index 3c6f24fc0..d2fbf5065 100644
--- a/resources/resource_transformers/js/build.go
+++ b/resources/resource_transformers/js/build.go
@@ -22,13 +22,14 @@ import (
 	"regexp"
 	"strings"
 
-	"github.com/pkg/errors"
+	"errors"
 
 	"github.com/spf13/afero"
 
 	"github.com/gohugoio/hugo/hugofs"
 
 	"github.com/gohugoio/hugo/common/herrors"
+	"github.com/gohugoio/hugo/common/text"
 
 	"github.com/gohugoio/hugo/hugolib/filesystems"
 	"github.com/gohugoio/hugo/media"
@@ -109,13 +110,13 @@ func (t *buildTransformation) Transform(ctx *resources.ResourceTransformationCtx
 		for i, ext := range opts.Inject {
 			impPath := filepath.FromSlash(ext)
 			if filepath.IsAbs(impPath) {
-				return errors.Errorf("inject: absolute paths not supported, must be relative to /assets")
+				return fmt.Errorf("inject: absolute paths not supported, must be relative to /assets")
 			}
 
 			m := resolveComponentInAssets(t.c.rs.Assets.Fs, impPath)
 
 			if m == nil {
-				return errors.Errorf("inject: file %q not found", ext)
+				return fmt.Errorf("inject: file %q not found", ext)
 			}
 
 			opts.Inject[i] = m.Filename
@@ -157,10 +158,12 @@ func (t *buildTransformation) Transform(ctx *resources.ResourceTransformationCtx
 			}
 
 			if err == nil {
-				fe := herrors.NewFileError("js", 0, loc.Line, loc.Column, errors.New(msg.Text))
-				err, _ := herrors.WithFileContext(fe, path, f, herrors.SimpleLineMatcher)
+				fe := herrors.NewFileError(path, errors.New(msg.Text)).
+					UpdatePosition(text.Position{Offset: -1, LineNumber: loc.Line, ColumnNumber: loc.Column}).
+					UpdateContent(f, herrors.SimpleLineMatcher)
+
 				f.Close()
-				return err
+				return fe
 			}
 
 			return fmt.Errorf("%s", msg.Text)
diff --git a/resources/resource_transformers/js/options.go b/resources/resource_transformers/js/options.go
index 675e40d43..a0d1b506f 100644
--- a/resources/resource_transformers/js/options.go
+++ b/resources/resource_transformers/js/options.go
@@ -21,7 +21,6 @@ import (
 	"strings"
 
 	"github.com/gohugoio/hugo/common/maps"
-	"github.com/pkg/errors"
 	"github.com/spf13/afero"
 
 	"github.com/evanw/esbuild/pkg/api"
@@ -251,7 +250,7 @@ func createBuildPlugins(c *Client, opts Options) ([]api.Plugin, error) {
 				func(args api.OnLoadArgs) (api.OnLoadResult, error) {
 					b, err := ioutil.ReadFile(args.Path)
 					if err != nil {
-						return api.OnLoadResult{}, errors.Wrapf(err, "failed to read %q", args.Path)
+						return api.OnLoadResult{}, fmt.Errorf("failed to read %q: %w", args.Path, err)
 					}
 					c := string(b)
 					return api.OnLoadResult{
@@ -274,7 +273,7 @@ func createBuildPlugins(c *Client, opts Options) ([]api.Plugin, error) {
 
 	b, err := json.Marshal(params)
 	if err != nil {
-		return nil, errors.Wrap(err, "failed to marshal params")
+		return nil, fmt.Errorf("failed to marshal params: %w", err)
 	}
 	bs := string(b)
 	paramsPlugin := api.Plugin{
diff --git a/resources/resource_transformers/postcss/postcss.go b/resources/resource_transformers/postcss/postcss.go
index 61209fb23..733c958cf 100644
--- a/resources/resource_transformers/postcss/postcss.go
+++ b/resources/resource_transformers/postcss/postcss.go
@@ -17,6 +17,7 @@ import (
 	"bytes"
 	"crypto/sha256"
 	"encoding/hex"
+	"fmt"
 	"io"
 	"io/ioutil"
 	"path"
@@ -36,8 +37,9 @@ import (
 	"github.com/spf13/afero"
 	"github.com/spf13/cast"
 
+	"errors"
+
 	"github.com/gohugoio/hugo/hugofs"
-	"github.com/pkg/errors"
 
 	"github.com/mitchellh/mapstructure"
 
@@ -161,7 +163,7 @@ func (t *postcssTransformation) Transform(ctx *resources.ResourceTransformationC
 		configFile = t.rs.BaseFs.ResolveJSConfigFile(configFile)
 		if configFile == "" && t.options.Config != "" {
 			// Only fail if the user specified config file is not found.
-			return errors.Errorf("postcss config %q not found:", configFile)
+			return fmt.Errorf("postcss config %q not found:", configFile)
 		}
 	}
 
@@ -388,15 +390,9 @@ func (imp *importResolver) toFileError(output string) error {
 	if err != nil {
 		return inErr
 	}
-	realFilename := fi.(hugofs.FileMetaInfo).Meta().Filename
-
-	ferr := herrors.NewFileError("css", -1, file.Offset+1, 1, inErr)
 
-	werr, ok := herrors.WithFileContextForFile(ferr, realFilename, file.Filename, imp.fs, herrors.SimpleLineMatcher)
+	realFilename := fi.(hugofs.FileMetaInfo).Meta().Filename
 
-	if !ok {
-		return ferr
-	}
+	return herrors.NewFileErrorFromFile(inErr, file.Filename, realFilename, hugofs.Os, herrors.SimpleLineMatcher)
 
-	return werr
 }
diff --git a/resources/resource_transformers/templates/execute_as_template.go b/resources/resource_transformers/templates/execute_as_template.go
index 5c2033ff9..5fe4230f1 100644
--- a/resources/resource_transformers/templates/execute_as_template.go
+++ b/resources/resource_transformers/templates/execute_as_template.go
@@ -15,12 +15,13 @@
 package templates
 
 import (
+	"fmt"
+
 	"github.com/gohugoio/hugo/helpers"
 	"github.com/gohugoio/hugo/resources"
 	"github.com/gohugoio/hugo/resources/internal"
 	"github.com/gohugoio/hugo/resources/resource"
 	"github.com/gohugoio/hugo/tpl"
-	"github.com/pkg/errors"
 )
 
 // Client contains methods to perform template processing of Resource objects.
@@ -55,7 +56,7 @@ func (t *executeAsTemplateTransform) Transform(ctx *resources.ResourceTransforma
 	tplStr := helpers.ReaderToString(ctx.From)
 	templ, err := t.t.TextTmpl().Parse(ctx.InPath, tplStr)
 	if err != nil {
-		return errors.Wrapf(err, "failed to parse Resource %q as Template:", ctx.InPath)
+		return fmt.Errorf("failed to parse Resource %q as Template:: %w", ctx.InPath, err)
 	}
 
 	ctx.OutPath = t.targetPath
diff --git a/resources/resource_transformers/tocss/dartsass/transform.go b/resources/resource_transformers/tocss/dartsass/transform.go
index 79c32fcfd..082e30710 100644
--- a/resources/resource_transformers/tocss/dartsass/transform.go
+++ b/resources/resource_transformers/tocss/dartsass/transform.go
@@ -120,18 +120,8 @@ func (t *transform) Transform(ctx *resources.ResourceTransformationCtx) error {
 				return m.Offset+len(m.Line) >= start.Offset && strings.Contains(m.Line, context)
 			}
 
-			ferr, ok := herrors.WithFileContextForFile(
-				herrors.NewFileError("scss", -1, -1, start.Column, sassErr),
-				filename,
-				filename,
-				hugofs.Os,
-				offsetMatcher)
-
-			if !ok {
-				return sassErr
-			}
+			return herrors.NewFileErrorFromFile(sassErr, filename, filename, hugofs.Os, offsetMatcher)
 
-			return ferr
 		}
 		return err
 	}
diff --git a/resources/resource_transformers/tocss/scss/tocss.go b/resources/resource_transformers/tocss/scss/tocss.go
index 802798e59..f9f4786f5 100644
--- a/resources/resource_transformers/tocss/scss/tocss.go
+++ b/resources/resource_transformers/tocss/scss/tocss.go
@@ -28,7 +28,6 @@ import (
 	"github.com/gohugoio/hugo/hugofs"
 	"github.com/gohugoio/hugo/media"
 	"github.com/gohugoio/hugo/resources"
-	"github.com/pkg/errors"
 )
 
 // Used in tests. This feature requires Hugo to be built with the extended tag.
@@ -172,7 +171,7 @@ func (c *Client) toCSS(options libsass.Options, dst io.Writer, src io.Reader) (l
 	in := helpers.ReaderToString(src)
 
 	// See https://github.com/gohugoio/hugo/issues/7059
-	// We need to preserver the regular CSS imports. This is by far
+	// We need to preserve the regular CSS imports. This is by far
 	// a perfect solution, and only works for the main entry file, but
 	// that should cover many use cases, e.g. using SCSS as a preprocessor
 	// for Tailwind.
@@ -181,7 +180,7 @@ func (c *Client) toCSS(options libsass.Options, dst io.Writer, src io.Reader) (l
 
 	res, err = transpiler.Execute(in)
 	if err != nil {
-		return res, errors.Wrap(err, "SCSS processing failed")
+		return res, fmt.Errorf("SCSS processing failed: %w", err)
 	}
 
 	out := res.CSS