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

7 files changed, 272 insertions, 252 deletions

diff --git a/common/herrors/error_locator.go b/common/herrors/error_locator.go
index 2c0d215b1..5d2c10c04 100644
--- a/common/herrors/error_locator.go
+++ b/common/herrors/error_locator.go
@@ -1,4 +1,4 @@
-// Copyright 2018 The Hugo Authors. All rights reserved.
+// Copyright 2022 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -21,8 +21,6 @@ import (
 	"strings"
 
 	"github.com/gohugoio/hugo/common/text"
-
-	"github.com/spf13/afero"
 )
 
 // LineMatcher contains the elements used to match an error to a line
@@ -43,8 +41,6 @@ var SimpleLineMatcher = func(m LineMatcher) bool {
 	return m.Position.LineNumber == m.LineNumber
 }
 
-var _ text.Positioner = ErrorContext{}
-
 // ErrorContext contains contextual information about an error. This will
 // typically be the lines surrounding some problem in a file.
 type ErrorContext struct {
@@ -56,125 +52,11 @@ type ErrorContext struct {
 	// The position of the error in the Lines above. 0 based.
 	LinesPos int
 
-	position text.Position
-
 	// The lexer to use for syntax highlighting.
 	// https://gohugo.io/content-management/syntax-highlighting/#list-of-chroma-highlighting-languages
 	ChromaLexer string
 }
 
-// Position returns the text position of this error.
-func (e ErrorContext) Position() text.Position {
-	return e.position
-}
-
-var _ causer = (*ErrorWithFileContext)(nil)
-
-// ErrorWithFileContext is an error with some additional file context related
-// to that error.
-type ErrorWithFileContext struct {
-	cause error
-	ErrorContext
-}
-
-func (e *ErrorWithFileContext) Error() string {
-	pos := e.Position()
-	if pos.IsValid() {
-		return pos.String() + ": " + e.cause.Error()
-	}
-	return e.cause.Error()
-}
-
-func (e *ErrorWithFileContext) Cause() error {
-	return e.cause
-}
-
-// WithFileContextForFile will try to add a file context with lines matching the given matcher.
-// If no match could be found, the original error is returned with false as the second return value.
-func WithFileContextForFile(e error, realFilename, filename string, fs afero.Fs, matcher LineMatcherFn) (error, bool) {
-	f, err := fs.Open(filename)
-	if err != nil {
-		return e, false
-	}
-	defer f.Close()
-	return WithFileContext(e, realFilename, f, matcher)
-}
-
-// WithFileContextForFileDefault tries to add file context using the default line matcher.
-func WithFileContextForFileDefault(err error, filename string, fs afero.Fs) error {
-	err, _ = WithFileContextForFile(
-		err,
-		filename,
-		filename,
-		fs,
-		SimpleLineMatcher)
-	return err
-}
-
-// WithFileContextForFile will try to add a file context with lines matching the given matcher.
-// If no match could be found, the original error is returned with false as the second return value.
-func WithFileContext(e error, realFilename string, r io.Reader, matcher LineMatcherFn) (error, bool) {
-	if e == nil {
-		panic("error missing")
-	}
-	le := UnwrapFileError(e)
-
-	if le == nil {
-		var ok bool
-		if le, ok = ToFileError("", e).(FileError); !ok {
-			return e, false
-		}
-	}
-
-	var errCtx ErrorContext
-
-	posle := le.Position()
-
-	if posle.Offset != -1 {
-		errCtx = locateError(r, le, func(m LineMatcher) bool {
-			if posle.Offset >= m.Offset && posle.Offset < m.Offset+len(m.Line) {
-				lno := posle.LineNumber - m.Position.LineNumber + m.LineNumber
-				m.Position = text.Position{LineNumber: lno}
-			}
-			return matcher(m)
-		})
-	} else {
-		errCtx = locateError(r, le, matcher)
-	}
-
-	pos := &errCtx.position
-
-	if pos.LineNumber == -1 {
-		return e, false
-	}
-
-	pos.Filename = realFilename
-
-	if le.Type() != "" {
-		errCtx.ChromaLexer = chromaLexerFromType(le.Type())
-	} else {
-		errCtx.ChromaLexer = chromaLexerFromFilename(realFilename)
-	}
-
-	return &ErrorWithFileContext{cause: e, ErrorContext: errCtx}, true
-}
-
-// UnwrapErrorWithFileContext tries to unwrap an ErrorWithFileContext from err.
-// It returns nil if this is not possible.
-func UnwrapErrorWithFileContext(err error) *ErrorWithFileContext {
-	for err != nil {
-		switch v := err.(type) {
-		case *ErrorWithFileContext:
-			return v
-		case causer:
-			err = v.Cause()
-		default:
-			return nil
-		}
-	}
-	return nil
-}
-
 func chromaLexerFromType(fileType string) string {
 	switch fileType {
 	case "html", "htm":
@@ -196,23 +78,23 @@ func chromaLexerFromFilename(filename string) string {
 	return chromaLexerFromType(ext)
 }
 
-func locateErrorInString(src string, matcher LineMatcherFn) ErrorContext {
+func locateErrorInString(src string, matcher LineMatcherFn) (*ErrorContext, text.Position) {
 	return locateError(strings.NewReader(src), &fileError{}, matcher)
 }
 
-func locateError(r io.Reader, le FileError, matches LineMatcherFn) ErrorContext {
+func locateError(r io.Reader, le FileError, matches LineMatcherFn) (*ErrorContext, text.Position) {
 	if le == nil {
 		panic("must provide an error")
 	}
 
-	errCtx := ErrorContext{position: text.Position{LineNumber: -1, ColumnNumber: 1, Offset: -1}, LinesPos: -1}
+	errCtx := &ErrorContext{LinesPos: -1}
+	pos := text.Position{LineNumber: -1, ColumnNumber: 1, Offset: -1}
 
 	b, err := ioutil.ReadAll(r)
 	if err != nil {
-		return errCtx
+		return errCtx, pos
 	}
 
-	pos := &errCtx.position
 	lepos := le.Position()
 
 	lines := strings.Split(string(b), "\n")
@@ -262,5 +144,5 @@ func locateError(r io.Reader, le FileError, matches LineMatcherFn) ErrorContext
 
 	}
 
-	return errCtx
+	return errCtx, pos
 }
diff --git a/common/herrors/error_locator_test.go b/common/herrors/error_locator_test.go
index 0cd5fb2d7..10b016fa8 100644
--- a/common/herrors/error_locator_test.go
+++ b/common/herrors/error_locator_test.go
@@ -1,4 +1,4 @@
-// Copyright 2018 The Hugo Authors. All rights reserved.
+// Copyright 2022 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -38,44 +38,48 @@ LINE 7
 LINE 8
 `
 
-	location := locateErrorInString(lines, lineMatcher)
+	location, pos := locateErrorInString(lines, lineMatcher)
 	c.Assert(location.Lines, qt.DeepEquals, []string{"LINE 3", "LINE 4", "This is THEONE", "LINE 6", "LINE 7"})
 
-	pos := location.Position()
 	c.Assert(pos.LineNumber, qt.Equals, 5)
 	c.Assert(location.LinesPos, qt.Equals, 2)
 
-	c.Assert(locateErrorInString(`This is THEONE`, lineMatcher).Lines, qt.DeepEquals, []string{"This is THEONE"})
+	locate := func(s string, m LineMatcherFn) *ErrorContext {
+		ctx, _ := locateErrorInString(s, m)
+		return ctx
+	}
+
+	c.Assert(locate(`This is THEONE`, lineMatcher).Lines, qt.DeepEquals, []string{"This is THEONE"})
 
-	location = locateErrorInString(`L1
+	location, pos = locateErrorInString(`L1
 This is THEONE
 L2
 `, lineMatcher)
-	c.Assert(location.Position().LineNumber, qt.Equals, 2)
+	c.Assert(pos.LineNumber, qt.Equals, 2)
 	c.Assert(location.LinesPos, qt.Equals, 1)
 	c.Assert(location.Lines, qt.DeepEquals, []string{"L1", "This is THEONE", "L2", ""})
 
-	location = locateErrorInString(`This is THEONE
+	location = locate(`This is THEONE
 L2
 `, lineMatcher)
 	c.Assert(location.LinesPos, qt.Equals, 0)
 	c.Assert(location.Lines, qt.DeepEquals, []string{"This is THEONE", "L2", ""})
 
-	location = locateErrorInString(`L1
+	location = locate(`L1
 This THEONE
 `, lineMatcher)
 	c.Assert(location.Lines, qt.DeepEquals, []string{"L1", "This THEONE", ""})
 	c.Assert(location.LinesPos, qt.Equals, 1)
 
-	location = locateErrorInString(`L1
+	location = locate(`L1
 L2
 This THEONE
 `, lineMatcher)
 	c.Assert(location.Lines, qt.DeepEquals, []string{"L1", "L2", "This THEONE", ""})
 	c.Assert(location.LinesPos, qt.Equals, 2)
 
-	location = locateErrorInString("NO MATCH", lineMatcher)
-	c.Assert(location.Position().LineNumber, qt.Equals, -1)
+	location, pos = locateErrorInString("NO MATCH", lineMatcher)
+	c.Assert(pos.LineNumber, qt.Equals, -1)
 	c.Assert(location.LinesPos, qt.Equals, -1)
 	c.Assert(len(location.Lines), qt.Equals, 0)
 
@@ -83,7 +87,7 @@ This THEONE
 		return m.LineNumber == 6
 	}
 
-	location = locateErrorInString(`A
+	location, pos = locateErrorInString(`A
 B
 C
 D
@@ -95,7 +99,7 @@ I
 J`, lineMatcher)
 
 	c.Assert(location.Lines, qt.DeepEquals, []string{"D", "E", "F", "G", "H"})
-	c.Assert(location.Position().LineNumber, qt.Equals, 6)
+	c.Assert(pos.LineNumber, qt.Equals, 6)
 	c.Assert(location.LinesPos, qt.Equals, 2)
 
 	// Test match EOF
@@ -103,26 +107,26 @@ J`, lineMatcher)
 		return m.LineNumber == 4
 	}
 
-	location = locateErrorInString(`A
+	location, pos = locateErrorInString(`A
 B
 C
 `, lineMatcher)
 
 	c.Assert(location.Lines, qt.DeepEquals, []string{"B", "C", ""})
-	c.Assert(location.Position().LineNumber, qt.Equals, 4)
+	c.Assert(pos.LineNumber, qt.Equals, 4)
 	c.Assert(location.LinesPos, qt.Equals, 2)
 
 	offsetMatcher := func(m LineMatcher) bool {
 		return m.Offset == 1
 	}
 
-	location = locateErrorInString(`A
+	location, pos = locateErrorInString(`A
 B
 C
 D
 E`, offsetMatcher)
 
 	c.Assert(location.Lines, qt.DeepEquals, []string{"A", "B", "C", "D"})
-	c.Assert(location.Position().LineNumber, qt.Equals, 2)
+	c.Assert(pos.LineNumber, qt.Equals, 2)
 	c.Assert(location.LinesPos, qt.Equals, 1)
 }
diff --git a/common/herrors/errors.go b/common/herrors/errors.go
index 27cfd2693..6ce908853 100644
--- a/common/herrors/errors.go
+++ b/common/herrors/errors.go
@@ -19,37 +19,11 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"os"
 	"runtime"
 	"runtime/debug"
 	"strconv"
-
-	_errors "github.com/pkg/errors"
 )
 
-// As defined in https://godoc.org/github.com/pkg/errors
-type causer interface {
-	Cause() error
-}
-
-type stackTracer interface {
-	StackTrace() _errors.StackTrace
-}
-
-// PrintStackTraceFromErr prints the error's stack trace to stdoud.
-func PrintStackTraceFromErr(err error) {
-	FprintStackTraceFromErr(os.Stdout, err)
-}
-
-// FprintStackTraceFromErr prints the error's stack trace to w.
-func FprintStackTraceFromErr(w io.Writer, err error) {
-	if err, ok := err.(stackTracer); ok {
-		for _, f := range err.StackTrace() {
-			fmt.Fprintf(w, "%+s:%d\n", f, f)
-		}
-	}
-}
-
 // PrintStackTrace prints the current stacktrace to w.
 func PrintStackTrace(w io.Writer) {
 	buf := make([]byte, 1<<16)
diff --git a/common/herrors/file_error.go b/common/herrors/file_error.go
index 1cb31ff9f..abd36cfbc 100644
--- a/common/herrors/file_error.go
+++ b/common/herrors/file_error.go
@@ -1,11 +1,11 @@
-// Copyright 2018 The Hugo Authors. All rights reserved.
+// Copyright 2022 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 // http://www.apache.org/licenses/LICENSE-2.0
 //
-// Unless required by applicable law or agreed to in writing, software
+// Unless required by applicable lfmtaw or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
@@ -15,59 +15,217 @@ package herrors
 
 import (
 	"encoding/json"
+	"fmt"
+	"io"
+	"path/filepath"
 
+	"github.com/gohugoio/hugo/common/paths"
 	"github.com/gohugoio/hugo/common/text"
+	"github.com/pelletier/go-toml/v2"
+	"github.com/spf13/afero"
+	"github.com/tdewolff/parse/v2"
 
-	"github.com/pkg/errors"
+	"errors"
 )
 
-var _ causer = (*fileError)(nil)
-
 // FileError represents an error when handling a file: Parsing a config file,
 // execute a template etc.
 type FileError interface {
 	error
 
+	// ErroContext holds some context information about the error.
+	ErrorContext() *ErrorContext
+
 	text.Positioner
 
-	// A string identifying the type of file, e.g. JSON, TOML, markdown etc.
-	Type() string
+	// UpdatePosition updates the position of the error.
+	UpdatePosition(pos text.Position) FileError
+
+	// UpdateContent updates the error with a new ErrorContext from the content of the file.
+	UpdateContent(r io.Reader, linematcher LineMatcherFn) FileError
+}
+
+// Unwrapper can unwrap errors created with fmt.Errorf.
+type Unwrapper interface {
+	Unwrap() error
 }
 
-var _ FileError = (*fileError)(nil)
+var (
+	_ FileError = (*fileError)(nil)
+	_ Unwrapper = (*fileError)(nil)
+)
+
+func (fe *fileError) UpdatePosition(pos text.Position) FileError {
+	oldFilename := fe.Position().Filename
+	if pos.Filename != "" && fe.fileType == "" {
+		_, fe.fileType = paths.FileAndExtNoDelimiter(filepath.Clean(pos.Filename))
+	}
+	if pos.Filename == "" {
+		pos.Filename = oldFilename
+	}
+	fe.position = pos
+	return fe
+}
+
+func (fe *fileError) UpdateContent(r io.Reader, linematcher LineMatcherFn) FileError {
+	if linematcher == nil {
+		linematcher = SimpleLineMatcher
+	}
+
+	var (
+		contentPos   text.Position
+		posle        = fe.position
+		errorContext *ErrorContext
+	)
+
+	if posle.LineNumber <= 1 && posle.Offset > 0 {
+		// Try to locate the line number from the content if offset is set.
+		errorContext, contentPos = locateError(r, fe, func(m LineMatcher) bool {
+			if posle.Offset >= m.Offset && posle.Offset < m.Offset+len(m.Line) {
+				lno := posle.LineNumber - m.Position.LineNumber + m.LineNumber
+				m.Position = text.Position{LineNumber: lno}
+				return linematcher(m)
+			}
+			return false
+		})
+	} else {
+		errorContext, contentPos = locateError(r, fe, linematcher)
+	}
+
+	if errorContext.ChromaLexer == "" {
+		if fe.fileType != "" {
+			errorContext.ChromaLexer = chromaLexerFromType(fe.fileType)
+		} else {
+			errorContext.ChromaLexer = chromaLexerFromFilename(fe.Position().Filename)
+		}
+	}
+
+	fe.errorContext = errorContext
+
+	if contentPos.LineNumber > 0 {
+		fe.position.LineNumber = contentPos.LineNumber
+	}
+
+	return fe
+
+}
 
 type fileError struct {
-	position text.Position
+	position     text.Position
+	errorContext *ErrorContext
 
 	fileType string
 
 	cause error
 }
 
+type fileErrorWithErrorContext struct {
+	*fileError
+}
+
+func (e *fileError) ErrorContext() *ErrorContext {
+	return e.errorContext
+}
+
 // Position returns the text position of this error.
 func (e fileError) Position() text.Position {
 	return e.position
 }
 
-func (e *fileError) Type() string {
-	return e.fileType
+func (e *fileError) Error() string {
+	return fmt.Sprintf("%s: %s", e.position, e.cause)
 }
 
-func (e *fileError) Error() string {
-	if e.cause == nil {
-		return ""
+func (e *fileError) Unwrap() error {
+	return e.cause
+}
+
+// NewFileError creates a new FileError that wraps err.
+// The value for name should identify the file, the best
+// being the full filename to the file on disk.
+func NewFileError(name string, err error) FileError {
+	if err == nil {
+		panic("err is nil")
+	}
+
+	// Filetype is used to determine the Chroma lexer to use.
+	fileType, pos := extractFileTypePos(err)
+	pos.Filename = name
+	if fileType == "" {
+		_, fileType = paths.FileAndExtNoDelimiter(filepath.Clean(name))
 	}
-	return e.cause.Error()
+
+	if pos.LineNumber < 0 {
+		panic(fmt.Sprintf("invalid line number: %d", pos.LineNumber))
+	}
+
+	return &fileError{cause: err, fileType: fileType, position: pos}
+
 }
 
-func (f *fileError) Cause() error {
-	return f.cause
+// NewFileErrorFromFile is a convenience method to create a new FileError from a file.
+func NewFileErrorFromFile(err error, filename, realFilename string, fs afero.Fs, linematcher LineMatcherFn) FileError {
+	if err == nil {
+		panic("err is nil")
+	}
+	if linematcher == nil {
+		linematcher = SimpleLineMatcher
+	}
+	f, err2 := fs.Open(filename)
+	if err2 != nil {
+		return NewFileError(realFilename, err)
+	}
+	defer f.Close()
+	return NewFileError(realFilename, err).UpdateContent(f, linematcher)
 }
 
-// NewFileError creates a new FileError.
-func NewFileError(fileType string, offset, lineNumber, columnNumber int, err error) FileError {
-	pos := text.Position{Offset: offset, LineNumber: lineNumber, ColumnNumber: columnNumber}
-	return &fileError{cause: err, fileType: fileType, position: pos}
+// Cause returns the underlying error or itself if it does not implement Unwrap.
+func Cause(err error) error {
+	if u := errors.Unwrap(err); u != nil {
+		return u
+	}
+	return err
+}
+
+func extractFileTypePos(err error) (string, text.Position) {
+	err = Cause(err)
+	var fileType string
+
+	// Fall back to line/col 1:1 if we cannot find any better information.
+	pos := text.Position{
+		Offset:       -1,
+		LineNumber:   1,
+		ColumnNumber: 1,
+	}
+
+	// JSON errors.
+	offset, typ := extractOffsetAndType(err)
+	if fileType == "" {
+		fileType = typ
+	}
+
+	if offset >= 0 {
+		pos.Offset = offset
+	}
+
+	// The error type from the minifier contains line number and column number.
+	if line, col := exctractLineNumberAndColumnNumber(err); line >= 0 {
+		pos.LineNumber = line
+		pos.ColumnNumber = col
+		return fileType, pos
+	}
+
+	// Look in the error message for the line number.
+	for _, handle := range lineNumberExtractors {
+		lno, col := handle(err)
+		if lno > 0 {
+			pos.ColumnNumber = col
+			pos.LineNumber = lno
+			break
+		}
+	}
+
+	return fileType, pos
 }
 
 // UnwrapFileError tries to unwrap a FileError from err.
@@ -77,49 +235,26 @@ func UnwrapFileError(err error) FileError {
 		switch v := err.(type) {
 		case FileError:
 			return v
-		case causer:
-			err = v.Cause()
 		default:
-			return nil
+			err = errors.Unwrap(err)
 		}
 	}
 	return nil
 }
 
-// ToFileErrorWithOffset will return a new FileError with a line number
-// with the given offset from the original.
-func ToFileErrorWithOffset(fe FileError, offset int) FileError {
-	pos := fe.Position()
-	return ToFileErrorWithLineNumber(fe, pos.LineNumber+offset)
-}
-
-// ToFileErrorWithOffset will return a new FileError with the given line number.
-func ToFileErrorWithLineNumber(fe FileError, lineNumber int) FileError {
-	pos := fe.Position()
-	pos.LineNumber = lineNumber
-	return &fileError{cause: fe, fileType: fe.Type(), position: pos}
-}
-
-// ToFileError will convert the given error to an error supporting
-// the FileError interface.
-func ToFileError(fileType string, err error) FileError {
-	for _, handle := range lineNumberExtractors {
-		lno, col := handle(err)
-		offset, typ := extractOffsetAndType(err)
-		if fileType == "" {
-			fileType = typ
-		}
-
-		if lno > 0 || offset != -1 {
-			return NewFileError(fileType, offset, lno, col, err)
+// UnwrapFileErrorsWithErrorContext tries to unwrap all FileError in err that has an ErrorContext.
+func UnwrapFileErrorsWithErrorContext(err error) []FileError {
+	var errs []FileError
+	for err != nil {
+		if v, ok := err.(FileError); ok && v.ErrorContext() != nil {
+			errs = append(errs, v)
 		}
+		err = errors.Unwrap(err)
 	}
-	// Fall back to the pointing to line number 1.
-	return NewFileError(fileType, -1, 1, 1, err)
+	return errs
 }
 
 func extractOffsetAndType(e error) (int, string) {
-	e = errors.Cause(e)
 	switch v := e.(type) {
 	case *json.UnmarshalTypeError:
 		return int(v.Offset), "json"
@@ -129,3 +264,15 @@ func extractOffsetAndType(e error) (int, string) {
 		return -1, ""
 	}
 }
+
+func exctractLineNumberAndColumnNumber(e error) (int, int) {
+	switch v := e.(type) {
+	case *parse.Error:
+		return v.Line, v.Column
+	case *toml.DecodeError:
+		return v.Position()
+
+	}
+
+	return -1, -1
+}
diff --git a/common/herrors/file_error_test.go b/common/herrors/file_error_test.go
index 675be94e8..e6595aa28 100644
--- a/common/herrors/file_error_test.go
+++ b/common/herrors/file_error_test.go
@@ -1,4 +1,4 @@
-// Copyright 2018 The Hugo Authors. All rights reserved.
+// Copyright 2022 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -14,14 +14,44 @@
 package herrors
 
 import (
+	"fmt"
+	"strings"
 	"testing"
 
-	"github.com/pkg/errors"
+	"errors"
+
+	"github.com/gohugoio/hugo/common/text"
 
 	qt "github.com/frankban/quicktest"
 )
 
-func TestToLineNumberError(t *testing.T) {
+func TestNewFileError(t *testing.T) {
+	t.Parallel()
+
+	c := qt.New(t)
+
+	fe := NewFileError("foo.html", errors.New("bar"))
+	c.Assert(fe.Error(), qt.Equals, `"foo.html:1:1": bar`)
+
+	lines := ""
+	for i := 1; i <= 100; i++ {
+		lines += fmt.Sprintf("line %d\n", i)
+	}
+
+	fe.UpdatePosition(text.Position{LineNumber: 32, ColumnNumber: 2})
+	c.Assert(fe.Error(), qt.Equals, `"foo.html:32:2": bar`)
+	fe.UpdatePosition(text.Position{LineNumber: 0, ColumnNumber: 0, Offset: 212})
+	fe.UpdateContent(strings.NewReader(lines), SimpleLineMatcher)
+	c.Assert(fe.Error(), qt.Equals, `"foo.html:32:0": bar`)
+	errorContext := fe.ErrorContext()
+	c.Assert(errorContext, qt.IsNotNil)
+	c.Assert(errorContext.Lines, qt.DeepEquals, []string{"line 30", "line 31", "line 32", "line 33", "line 34"})
+	c.Assert(errorContext.LinesPos, qt.Equals, 2)
+	c.Assert(errorContext.ChromaLexer, qt.Equals, "go-html-template")
+
+}
+
+func TestNewFileErrorExtractFromMessage(t *testing.T) {
 	t.Parallel()
 
 	c := qt.New(t)
@@ -37,18 +67,16 @@ func TestToLineNumberError(t *testing.T) {
 		{errors.New("parse failed: template: _default/bundle-resource-meta.html:11: unexpected in operand"), 0, 11, 1},
 		{errors.New(`failed:: template: _default/bundle-resource-meta.html:2:7: executing "main" at <.Titles>`), 0, 2, 7},
 		{errors.New(`failed to load translations: (6, 7): was expecting token =, but got "g" instead`), 0, 6, 7},
+		{errors.New(`execute of template failed: template: index.html:2:5: executing "index.html" at <partial "foo.html" .>: error calling partial: "/layouts/partials/foo.html:3:6": execute of template failed: template: partials/foo.html:3:6: executing "partials/foo.html" at <.ThisDoesNotExist>: can't evaluate field ThisDoesNotExist in type *hugolib.pageStat`), 0, 2, 5},
 	} {
 
-		got := ToFileError("template", test.in)
+		got := NewFileError("test.txt", test.in)
 
 		errMsg := qt.Commentf("[%d][%T]", i, got)
-		le, ok := got.(FileError)
-		c.Assert(ok, qt.Equals, true)
 
-		c.Assert(ok, qt.Equals, true, errMsg)
-		pos := le.Position()
+		pos := got.Position()
 		c.Assert(pos.LineNumber, qt.Equals, test.lineNumber, errMsg)
 		c.Assert(pos.ColumnNumber, qt.Equals, test.columnNumber, errMsg)
-		c.Assert(errors.Cause(got), qt.Not(qt.IsNil))
+		c.Assert(errors.Unwrap(got), qt.Not(qt.IsNil))
 	}
 }
diff --git a/common/herrors/line_number_extractors.go b/common/herrors/line_number_extractors.go
index 3df62bdfe..f70a2691f 100644
--- a/common/herrors/line_number_extractors.go
+++ b/common/herrors/line_number_extractors.go
@@ -16,36 +16,22 @@ package herrors
 import (
 	"regexp"
 	"strconv"
-
-	"github.com/pkg/errors"
-
-	"github.com/pelletier/go-toml/v2"
 )
 
 var lineNumberExtractors = []lineNumberExtractor{
 	// Template/shortcode parse errors
-	newLineNumberErrHandlerFromRegexp(".*:(\\d+):(\\d*):"),
-	newLineNumberErrHandlerFromRegexp(".*:(\\d+):"),
+	newLineNumberErrHandlerFromRegexp(`:(\d+):(\d*):`),
+	newLineNumberErrHandlerFromRegexp(`:(\d+):`),
 
-	// TOML parse errors
-	tomlLineNumberExtractor,
 	// YAML parse errors
-	newLineNumberErrHandlerFromRegexp("line (\\d+):"),
+	newLineNumberErrHandlerFromRegexp(`line (\d+):`),
 
 	// i18n bundle errors
-	newLineNumberErrHandlerFromRegexp("\\((\\d+),\\s(\\d*)"),
+	newLineNumberErrHandlerFromRegexp(`\((\d+),\s(\d*)`),
 }
 
 type lineNumberExtractor func(e error) (int, int)
 
-var tomlLineNumberExtractor = func(e error) (int, int) {
-	e = errors.Cause(e)
-	if terr, ok := e.(*toml.DecodeError); ok {
-		return terr.Position()
-	}
-	return -1, -1
-}
-
 func newLineNumberErrHandlerFromRegexp(expression string) lineNumberExtractor {
 	re := regexp.MustCompile(expression)
 	return extractLineNo(re)
@@ -72,6 +58,6 @@ func extractLineNo(re *regexp.Regexp) lineNumberExtractor {
 			return lno, col
 		}
 
-		return -1, col
+		return 0, col
 	}
 }
diff --git a/common/hugio/copy.go b/common/hugio/copy.go
index be4506f4c..7c52f8723 100644
--- a/common/hugio/copy.go
+++ b/common/hugio/copy.go
@@ -14,13 +14,12 @@
 package hugio
 
 import (
+	"fmt"
 	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
 
-	"github.com/pkg/errors"
-
 	"github.com/spf13/afero"
 )
 
@@ -60,7 +59,7 @@ func CopyDir(fs afero.Fs, from, to string, shouldCopy func(filename string) bool
 	}
 
 	if !fi.IsDir() {
-		return errors.Errorf("%q is not a directory", from)
+		return fmt.Errorf("%q is not a directory", from)
 	}
 
 	err = fs.MkdirAll(to, 0777) // before umask