big overhaul of error-formatting, to get positions more consistently

fixes #2

generate/comments.go

@@ -40,6 +40,8 @@ import (
 // the directive "a" is ignored, "b" and "c" apply to all relevant nodes in the
 // query, "d" applies to arg2 and arg3, and "e" applies to field1 and field2.
 type GenqlientDirective struct {
+	pos *ast.Position
+
 	// If set, this argument will be omitted if it's equal to its Go zero
 	// value.  For example, given the following query:
 	//	# @genqlient(omitempty: true)
@@ -68,23 +70,25 @@ func setBool(dst **bool, v *ast.Value) error {
 	ei, err := v.Value(nil) // no vars allowed
 	// TODO: here and below, put positions on these errors
 	if err != nil {
-		return fmt.Errorf("invalid boolean value %v: %w", v, err)
+		return errorf(v.Position, "invalid boolean value %v: %v", v, err)
 	}
 	if b, ok := ei.(bool); ok {
 		*dst = &b
 		return nil
 	}
-	return fmt.Errorf("expected boolean, got non-boolean value %T(%v)", ei, ei)
+	return errorf(v.Position, "expected boolean, got non-boolean value %T(%v)", ei, ei)
 }
 
 func fromGraphQL(dir *ast.Directive) (*GenqlientDirective, error) {
 	if dir.Name != "genqlient" {
 		// Actually we just won't get here; we only get here if the line starts
 		// with "# @genqlient", unless there's some sort of bug.
-		return nil, fmt.Errorf("the only valid comment-directive is @genqlient, got %v", dir.Name)
+		return nil, errorf(dir.Position, "the only valid comment-directive is @genqlient, got %v", dir.Name)
 	}
 
 	var retval GenqlientDirective
+	retval.pos = dir.Position
+
 	var err error
 	for _, arg := range dir.Arguments {
 		switch arg.Name {
@@ -94,7 +98,7 @@ func fromGraphQL(dir *ast.Directive) (*GenqlientDirective, error) {
 		case "pointer":
 			err = setBool(&retval.Pointer, arg.Value)
 		default:
-			return nil, fmt.Errorf("unknown argument %v for @genqlient", arg.Name)
+			return nil, errorf(arg.Position, "unknown argument %v for @genqlient", arg.Name)
 		}
 		if err != nil {
 			return nil, err
@@ -111,16 +115,16 @@ func (dir *GenqlientDirective) validate(node interface{}) error {
 		return nil
 	case *ast.VariableDefinition:
 		if dir.Omitempty != nil && node.Type.NonNull {
-			return fmt.Errorf("omitempty may only be used on optional arguments")
+			return errorf(dir.pos, "omitempty may only be used on optional arguments")
 		}
 		return nil
 	case *ast.Field:
 		if dir.Omitempty != nil {
-			return fmt.Errorf("omitempty is not appilcable to fields")
+			return errorf(dir.pos, "omitempty is not appilcable to fields")
 		}
 		return nil
 	default:
-		return fmt.Errorf("invalid directive location: %T", node)
+		return errorf(dir.pos, "invalid directive location: %T", node)
 	}
 }
 
@@ -174,13 +178,9 @@ func (g *generator) parsePrecedingComment(
 func parseDirective(line string, pos *ast.Position) (*ast.Directive, error) {
 	// HACK: parse the "directive" by making a fake query containing it.
 	fakeQuery := fmt.Sprintf("query %v { field }", line)
-	doc, err := parser.ParseQuery(&ast.Source{
-		Name: fmt.Sprintf("@genqlient directive at %v:%v:%v",
-			pos.Src.Name, pos.Line, pos.Column),
-		Input: fakeQuery,
-	})
+	doc, err := parser.ParseQuery(&ast.Source{Input: fakeQuery})
 	if err != nil {
-		return nil, err
+		return nil, errorf(pos, "invalid genqlient directive: %v", err)
 	}
 	return doc.Operations[0].Directives[0], nil
 }

generate/config.go

@@ -1,7 +1,6 @@
 package generate
 
 import (
-	"fmt"
 	"go/token"
 	"io/ioutil"
 	"path/filepath"
@@ -103,12 +102,12 @@ func (c *Config) ValidateAndFillDefaults(configFilename string) error {
 	if c.Package == "" {
 		abs, err := filepath.Abs(c.Generated)
 		if err != nil {
-			return fmt.Errorf("unable to guess package-name: %v", err)
+			return errorf(nil, "unable to guess package-name: %v", err)
 		}
 
 		base := filepath.Base(filepath.Dir(abs))
 		if !token.IsIdentifier(base) {
-			return fmt.Errorf("unable to guess package-name: %v is not a valid identifier", base)
+			return errorf(nil, "unable to guess package-name: %v is not a valid identifier", base)
 		}
 
 		c.Package = base
@@ -122,18 +121,18 @@ func ReadAndValidateConfig(filename string) (*Config, error) {
 	if filename != "" {
 		text, err := ioutil.ReadFile(filename)
 		if err != nil {
-			return nil, fmt.Errorf("unreadable config file %v: %v", filename, err)
+			return nil, errorf(nil, "unreadable config file %v: %v", filename, err)
 		}
 
 		err = yaml.Unmarshal(text, &config)
 		if err != nil {
-			return nil, fmt.Errorf("invalid config file %v: %v", filename, err)
+			return nil, errorf(nil, "invalid config file %v: %v", filename, err)
 		}
 	}
 
 	err := config.ValidateAndFillDefaults(filename)
 	if err != nil {
-		return nil, fmt.Errorf("invalid config file %v: %v", filename, err)
+		return nil, errorf(nil, "invalid config file %v: %v", filename, err)
 	}
 
 	return &config, nil

generate/errors.go

@@ -0,0 +1,132 @@
+package generate
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/vektah/gqlparser/v2/ast"
+	"github.com/vektah/gqlparser/v2/gqlerror"
+)
+
+type errorPos struct {
+	filename  string
+	line, col int
+}
+
+func (pos *errorPos) String() string {
+	filename, lineOffset := splitFilename(pos.filename)
+	line := lineOffset + pos.line
+	if line != 0 {
+		return fmt.Sprintf("%v:%v", filename, line)
+	} else {
+		return filename
+	}
+}
+
+type genqlientError struct {
+	pos     *errorPos
+	msg     string
+	wrapped error
+}
+
+func splitFilename(filename string) (name string, lineOffset int) {
+	split := strings.Split(filename, ":")
+	if len(split) != 2 {
+		return filename, 0
+	}
+
+	offset, err := strconv.Atoi(split[1])
+	if err != nil {
+		return split[0], 0
+	}
+	return split[0], offset - 1
+}
+
+func (err *genqlientError) Error() string {
+	if err.pos != nil {
+		return err.pos.String() + ": " + err.msg
+	} else {
+		return err.msg
+	}
+}
+
+func (err *genqlientError) Unwrap() error {
+	return err.wrapped
+}
+
+func errorf(pos *ast.Position, msg string, args ...interface{}) error {
+	// TODO: alternately accept a filename only, or maybe even a go-parser pos
+
+	// We do all our own wrapping, because if the wrapped error already has a
+	// pos, we want to extract it out and put it at the front, not in the
+	// middle.
+
+	var wrapped error
+	var wrapIndex int
+	for i, arg := range args {
+		if wrapped == nil {
+			var ok bool
+			wrapped, ok = arg.(error)
+			if ok {
+				wrapIndex = i
+			}
+		}
+	}
+
+	var wrappedGenqlient *genqlientError
+	isGenqlient := errors.As(wrapped, &wrappedGenqlient)
+	var wrappedGraphQL *gqlerror.Error
+	isGraphQL := errors.As(wrapped, &wrappedGraphQL)
+	if !isGraphQL {
+		var wrappedGraphQLList gqlerror.List
+		isGraphQLList := errors.As(wrapped, &wrappedGraphQLList)
+		if isGraphQLList && len(wrappedGraphQLList) > 0 {
+			isGraphQL = true
+			wrappedGraphQL = wrappedGraphQLList[0]
+		}
+	}
+
+	var errPos *errorPos
+	if pos != nil {
+		errPos = &errorPos{
+			filename: pos.Src.Name,
+			line:     pos.Line,
+			col:      pos.Column,
+		}
+	} else if isGenqlient {
+		errPos = wrappedGenqlient.pos
+	} else if isGraphQL {
+		filename, _ := wrappedGraphQL.Extensions["file"].(string)
+		if filename != "" {
+			var loc gqlerror.Location
+			if len(wrappedGraphQL.Locations) > 0 {
+				loc = wrappedGraphQL.Locations[0]
+			}
+			errPos = &errorPos{
+				filename: filename,
+				line:     loc.Line,
+				col:      loc.Column,
+			}
+		}
+	}
+
+	if wrapped != nil {
+		errText := wrapped.Error()
+		if isGenqlient {
+			errText = wrappedGenqlient.msg
+		} else if isGraphQL {
+			errText = wrappedGraphQL.Message
+		}
+		args[wrapIndex] = errText
+	}
+
+	msg = fmt.Sprintf(msg, args...)
+
+	return &genqlientError{
+		msg:     msg,
+		pos:     errPos,
+		wrapped: wrapped,
+	}
+}

generate/generate.go

@@ -3,7 +3,6 @@ package generate
 import (
 	"bytes"
 	"encoding/json"
-	"fmt"
 	"go/format"
 	"sort"
 	"strings"
@@ -134,7 +133,7 @@ func (g *generator) getArgument(
 
 func (g *generator) addOperation(op *ast.OperationDefinition) error {
 	if op.Name == "" {
-		return fmt.Errorf("operations must have operation-names")
+		return errorf(op.Position, "operations must have operation-names")
 	}
 
 	var builder strings.Builder
@@ -199,11 +198,14 @@ func Generate(config *Config) (map[string][]byte, error) {
 	// package-name, if it turns out to be more convenient that way.  (As-is,
 	// we generate a broken file, with just (unused) imports.)
 	if len(document.Operations) == 0 {
-		return nil, fmt.Errorf("no queries found in %v", config.Operations)
+		// Hard to have a position when there are no operations :(
+		return nil, errorf(nil, "no queries found, looked in: %v",
+			strings.Join(config.Operations, ", "))
 	}
 
 	if len(document.Fragments) > 0 && !allowBrokenFeatures {
-		return nil, fmt.Errorf("genqlient does not yet support fragments")
+		return nil, errorf(document.Fragments[0].Position,
+			"genqlient does not yet support fragments")
 	}
 
 	g := newGenerator(config, schema)
@@ -216,18 +218,18 @@ func Generate(config *Config) (map[string][]byte, error) {
 	var buf bytes.Buffer
 	err = g.execute("operation.go.tmpl", &buf, g)
 	if err != nil {
-		return nil, fmt.Errorf("could not render template: %v", err)
+		return nil, errorf(nil, "could not render template: %v", err)
 	}
 
 	unformatted := buf.Bytes()
 	formatted, err := format.Source(unformatted)
 	if err != nil {
-		return nil, fmt.Errorf("could not gofmt code: %v\n---unformatted code---\n%v",
+		return nil, errorf(nil, "could not gofmt code: %v\n---unformatted code---\n%v",
 			err, string(unformatted))
 	}
 	importsed, err := imports.Process(config.Generated, formatted, nil)
 	if err != nil {
-		return nil, fmt.Errorf("could not goimports code: %v\n---unimportsed code---\n%v",
+		return nil, errorf(nil, "could not goimports code: %v\n---unimportsed code---\n%v",
 			err, string(formatted))
 	}
 
@@ -243,7 +245,7 @@ func Generate(config *Config) (map[string][]byte, error) {
 		retval[config.ExportOperations], err = json.MarshalIndent(
 			exportedOperations{Operations: g.Operations}, "", "  ")
 		if err != nil {
-			return nil, fmt.Errorf("unable to export queries: %v", err)
+			return nil, errorf(nil, "unable to export queries: %v", err)
 		}
 	}
 

generate/generate_test.go

@@ -2,7 +2,6 @@ package generate
 
 import (
 	"errors"
-	"fmt"
 	"go/format"
 	"io/ioutil"
 	"os"
@@ -20,7 +19,7 @@ func gofmt(filename, src string) (string, error) {
 	src = strings.TrimSpace(src)
 	formatted, err := format.Source([]byte(src))
 	if err != nil {
-		return src, fmt.Errorf("go parse error in %v: %w", filename, err)
+		return src, errorf(nil, "go parse error in %v: %v", filename, err)
 	}
 	return string(formatted), nil
 }

generate/imports.go

@@ -1,7 +1,6 @@
 package generate
 
 import (
-	"fmt"
 	"go/types"
 	"strconv"
 	"strings"
@@ -45,7 +44,8 @@ func (g *generator) getRef(fullyQualifiedName string, addImport bool) (qualified
 		// confusing, why would you want it.  But the empty interface,
 		// specifically, is useful.
 		if fullyQualifiedName != "interface{}" && types.Universe.Lookup(fullyQualifiedName) == nil {
-			return "", fmt.Errorf(
+			// TODO: pass in pos here
+			return "", errorf(nil,
 				`unknown name "%v"; expected a builtin or path/to/package.Name`, fullyQualifiedName)
 		}
 		return fullyQualifiedName, nil
@@ -60,7 +60,7 @@ func (g *generator) getRef(fullyQualifiedName string, addImport bool) (qualified
 		var ok bool
 		alias, ok = g.imports[pkgPath]
 		if !ok {
-			return "", fmt.Errorf(`no alias defined for package "%v"`, pkgPath)
+			return "", errorf(nil, `no alias defined for package "%v"`, pkgPath)
 		}
 	}
 	return alias + "." + localName, nil

generate/main.go

@@ -5,6 +5,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"strings"
 )
 
 func readConfigGenerateAndWrite(configFilename string) error {
@@ -21,14 +22,14 @@ func readConfigGenerateAndWrite(configFilename string) error {
 	for filename, content := range generated {
 		err = os.MkdirAll(filepath.Dir(filename), 0o755)
 		if err != nil {
-			return fmt.Errorf(
+			return errorf(nil,
 				"could not create parent directory for generated file %v: %v",
 				filename, err)
 		}
 
 		err = ioutil.WriteFile(filename, content, 0o644)
 		if err != nil {
-			return fmt.Errorf("could not write generated file %v: %v",
+			return errorf(nil, "could not write generated file %v: %v",
 				filename, err)
 		}
 	}
@@ -50,6 +51,10 @@ func Main() {
 	case 1:
 		err = readConfigGenerateAndWrite("")
 	default:
-		err = fmt.Errorf("usage: %s [config]", os.Args[0])
+		argv0 := os.Args[0]
+		if strings.Contains(argv0, string(filepath.Separator)+"go-build") {
+			argv0 = "go run github.com/Khan/genqlient"
+		}
+		err = errorf(nil, "usage: %s [config]", argv0)
 	}
 }

generate/parse.go

@@ -20,13 +20,13 @@ import (
 func getSchema(filename string) (*ast.Schema, error) {
 	text, err := ioutil.ReadFile(filename)
 	if err != nil {
-		return nil, fmt.Errorf("unreadable schema file %v: %v", filename, err)
+		return nil, errorf(nil, "unreadable schema file %v: %v", filename, err)
 	}
 
 	schema, graphqlError := gqlparser.LoadSchema(
 		&ast.Source{Name: filename, Input: string(text)})
 	if graphqlError != nil {
-		return nil, fmt.Errorf("invalid schema file %v: %v",
+		return nil, errorf(nil, "invalid schema file %v: %v",
 			filename, graphqlError)
 	}
 
@@ -42,7 +42,7 @@ func getAndValidateQueries(basedir string, filenames []string, schema *ast.Schem
 	// Cf. gqlparser.LoadQuery
 	graphqlErrors := validator.Validate(schema, queryDoc)
 	if graphqlErrors != nil {
-		return nil, fmt.Errorf("query-spec does not match schema: %v", graphqlErrors)
+		return nil, errorf(nil, "query-spec does not match schema: %v", graphqlErrors)
 	}
 
 	return queryDoc, nil
@@ -64,7 +64,7 @@ func getQueries(basedir string, filenames []string) (*ast.QueryDocument, error)
 	for _, filename := range filenames {
 		matches, err := filepath.Glob(filename)
 		if err != nil {
-			return nil, fmt.Errorf("can't expand file-glob %v: %v", filename, err)
+			return nil, errorf(nil, "can't expand file-glob %v: %v", filename, err)
 		}
 		expandedFilenames = append(expandedFilenames, matches...)
 	}
@@ -72,7 +72,7 @@ func getQueries(basedir string, filenames []string) (*ast.QueryDocument, error)
 	for _, filename := range expandedFilenames {
 		text, err := ioutil.ReadFile(filename)
 		if err != nil {
-			return nil, fmt.Errorf("unreadable query-spec file %v: %v", filename, err)
+			return nil, errorf(nil, "unreadable query-spec file %v: %v", filename, err)
 		}
 
 		switch filepath.Ext(filename) {
@@ -95,7 +95,7 @@ func getQueries(basedir string, filenames []string) (*ast.QueryDocument, error)
 			}
 
 		default:
-			return nil, fmt.Errorf("unknown file type: %v", filename)
+			return nil, errorf(nil, "unknown file type: %v", filename)
 		}
 	}
 
@@ -113,7 +113,7 @@ func getQueriesFromString(text string, basedir, filename string) (*ast.QueryDocu
 	document, graphqlError := parser.ParseQuery(
 		&ast.Source{Name: filename, Input: text})
 	if graphqlError != nil { // ParseQuery returns type *graphql.Error, yuck
-		return nil, fmt.Errorf("invalid query-spec file %v: %v", filename, graphqlError)
+		return nil, errorf(nil, "invalid query-spec file %v: %v", filename, graphqlError)
 	}
 
 	return document, nil
@@ -123,7 +123,7 @@ func getQueriesFromGo(text string, basedir, filename string) ([]*ast.QueryDocume
 	fset := goToken.NewFileSet()
 	f, err := goParser.ParseFile(fset, filename, text, 0)
 	if err != nil {
-		return nil, fmt.Errorf("invalid Go file %v: %v", filename, err)
+		return nil, errorf(nil, "invalid Go file %v: %v", filename, err)
 	}
 
 	var retval []*ast.QueryDocument
@@ -147,9 +147,13 @@ func getQueriesFromGo(text string, basedir, filename string) ([]*ast.QueryDocume
 			return true
 		}
 
-		filename := fset.Position(basicLit.Pos()).Filename
+		// We put the filename as <real filename>:<line>, which errors.go knows
+		// how to parse back out (since it's what gqlparser will give to us in
+		// our errors).
+		pos := fset.Position(basicLit.Pos())
+		fakeFilename := fmt.Sprintf("%v:%v", pos.Filename, pos.Line)
 		var query *ast.QueryDocument
-		query, err = getQueriesFromString(value, basedir, filename)
+		query, err = getQueriesFromString(value, basedir, fakeFilename)
 		if err != nil {
 			return false
 		}

generate/template.go

@@ -1,7 +1,6 @@
 package generate
 
 import (
-	"fmt"
 	"io"
 	"path/filepath"
 	"runtime"
@@ -26,13 +25,13 @@ func (g *generator) execute(tmplRelFilename string, w io.Writer, data interface{
 		var err error
 		tmpl, err = template.New(tmplRelFilename).Funcs(funcMap).ParseFiles(absFilename)
 		if err != nil {
-			return fmt.Errorf("could not load template %v: %v", absFilename, err)
+			return errorf(nil, "could not load template %v: %v", absFilename, err)
 		}
 		g.templateCache[tmplRelFilename] = tmpl
 	}
 	err := tmpl.Execute(w, data)
 	if err != nil {
-		return fmt.Errorf("could not render template: %v", err)
+		return errorf(nil, "could not render template: %v", err)
 	}
 	return nil
 }

generate/testdata/errors/InvalidQuery.go.error

@@ -1 +1 @@
-query-spec does not match schema: testdata/errors/InvalidQuery.go:2: Cannot query field "g" on type "Query". Did you mean "f"?
+testdata/errors/InvalidQuery.go:4: query-spec does not match schema: Cannot query field "g" on type "Query". Did you mean "f"?

generate/testdata/errors/InvalidQuery.graphql.error

@@ -1 +1 @@
-query-spec does not match schema: testdata/errors/InvalidQuery.graphql:1: Cannot query field "g" on type "Query". Did you mean "f"?
+testdata/errors/InvalidQuery.graphql:1: query-spec does not match schema: Cannot query field "g" on type "Query". Did you mean "f"?

generate/testdata/errors/InvalidSchema.go.error

@@ -1 +1 @@
-invalid schema file testdata/errors/InvalidSchema.schema.graphql: testdata/errors/InvalidSchema.schema.graphql:4: Expected :, found }
+testdata/errors/InvalidSchema.schema.graphql:4: invalid schema file testdata/errors/InvalidSchema.schema.graphql: Expected :, found }

generate/testdata/errors/InvalidSchema.graphql.error

@@ -1 +1 @@
-invalid schema file testdata/errors/InvalidSchema.schema.graphql: testdata/errors/InvalidSchema.schema.graphql:4: Expected :, found }
+testdata/errors/InvalidSchema.schema.graphql:4: invalid schema file testdata/errors/InvalidSchema.schema.graphql: Expected :, found }

generate/testdata/errors/NoQuery.go.error

@@ -1 +1 @@
-no queries found in [testdata/errors/NoQuery.go]
+no queries found, looked in: testdata/errors/NoQuery.go

generate/testdata/errors/NoQuery.graphql.error

@@ -1 +1 @@
-no queries found in [testdata/errors/NoQuery.graphql]
+no queries found, looked in: testdata/errors/NoQuery.graphql

generate/testdata/errors/UnknownScalar.go.error

@@ -1 +1 @@
-unknown scalar UnknownScalar: please add it to genqlient.yaml
+testdata/errors/UnknownScalar.schema.graphql:3: unknown scalar UnknownScalar: please add it to genqlient.yaml

generate/testdata/errors/UnknownScalar.graphql.error

@@ -1 +1 @@
-unknown scalar UnknownScalar: please add it to genqlient.yaml
+testdata/errors/UnknownScalar.schema.graphql:3: unknown scalar UnknownScalar: please add it to genqlient.yaml

generate/types.go

@@ -22,11 +22,11 @@ func (g *generator) baseTypeForOperation(operation ast.Operation) (*ast.Definiti
 		return g.schema.Mutation, nil
 	case ast.Subscription:
 		if !allowBrokenFeatures {
-			return nil, fmt.Errorf("genqlient does not yet support subscriptions")
+			return nil, errorf(nil, "genqlient does not yet support subscriptions")
 		}
 		return g.schema.Subscription, nil
 	default:
-		return nil, fmt.Errorf("unexpected operation: %v", operation)
+		return nil, errorf(nil, "unexpected operation: %v", operation)
 	}
 }
 
@@ -36,7 +36,7 @@ func (g *generator) getTypeForOperation(operation *ast.OperationDefinition, quer
 
 	if def, ok := g.typeMap[name]; ok {
 		// TODO: check for and handle conflicts a better way
-		return "", fmt.Errorf("%s defined twice:\n%s", name, def)
+		return "", errorf(operation.Position, "%s defined twice:\n%s", name, def)
 	}
 
 	fields, err := selections(g, operation.SelectionSet, queryOptions)
@@ -46,10 +46,10 @@ func (g *generator) getTypeForOperation(operation *ast.OperationDefinition, quer
 
 	baseType, err := g.baseTypeForOperation(operation.Operation)
 	if err != nil {
-		return "", err
+		return "", errorf(operation.Position, "%v", err)
 	}
 
-	return g.addTypeForDefinition(operation.Name, name, baseType, fields, queryOptions)
+	return g.addTypeForDefinition(operation.Name, name, baseType, operation.Position, fields, queryOptions)
 }
 
 var builtinTypes = map[string]string{
@@ -61,7 +61,13 @@ var builtinTypes = map[string]string{
 	"ID":      "string",
 }
 
-func (g *generator) addTypeForDefinition(namePrefix, nameOverride string, typ *ast.Definition, fields []field, options *GenqlientDirective) (name string, err error) {
+func (g *generator) addTypeForDefinition(
+	namePrefix, nameOverride string,
+	typ *ast.Definition,
+	pos *ast.Position,
+	fields []field,
+	options *GenqlientDirective,
+) (name string, err error) {
 	// If this is a builtin type or custom scalar, just refer to it.
 	goName, ok := g.Config.Scalars[typ.Name]
 	if ok {
@@ -114,7 +120,7 @@ func (g *generator) addTypeForDefinition(namePrefix, nameOverride string, typ *a
 	// name.
 	builder := &typeBuilder{typeName: name, typeNamePrefix: namePrefix, generator: g}
 	fmt.Fprintf(builder, "type %s ", name)
-	err = builder.writeTypedef(typ, fields, options)
+	err = builder.writeTypedef(typ, pos, fields, options)
 	if err != nil {
 		return "", err
 	}
@@ -146,6 +152,7 @@ type field interface {
 	Alias() string
 	Options() (*GenqlientDirective, error)
 	Type() *ast.Type
+	Pos() *ast.Position
 	SubFields() ([]field, error)
 }
 
@@ -176,6 +183,10 @@ func (s outputField) Type() *ast.Type {
 	return s.field.Definition.Type
 }
 
+func (s outputField) Pos() *ast.Position {
+	return s.field.Position
+}
+
 func (s outputField) SubFields() ([]field, error) {
 	return selections(s.generator, s.field.SelectionSet, s.queryOptions)
 }
@@ -186,10 +197,12 @@ func selections(g *generator, selectionSet ast.SelectionSet, options *GenqlientD
 		switch selection := selection.(type) {
 		case *ast.Field:
 			retval[i] = outputField{g, options, selection}
-		case *ast.FragmentSpread, *ast.InlineFragment:
-			return nil, fmt.Errorf("not implemented: %T", selection)
+		case *ast.FragmentSpread:
+			return nil, errorf(selection.Position, "not implemented: %T", selection)
+		case *ast.InlineFragment:
+			return nil, errorf(selection.Position, "not implemented: %T", selection)
 		default:
-			return nil, fmt.Errorf("invalid selection type: %v", selection)
+			return nil, errorf(nil, "invalid selection type: %T", selection)
 		}
 	}
 	return retval, nil
@@ -209,7 +222,8 @@ func (s inputField) Options() (*GenqlientDirective, error) {
 	}
 	return s.queryOptions.merge(directive), nil
 }
-func (s inputField) Type() *ast.Type { return s.field.Type }
+func (s inputField) Type() *ast.Type    { return s.field.Type }
+func (s inputField) Pos() *ast.Position { return s.field.Position }
 
 func (s inputField) SubFields() ([]field, error) {
 	return selectionsForType(s.generator, s.field.Type, s.queryOptions), nil
@@ -236,7 +250,7 @@ func (builder *typeBuilder) writeField(field field) error {
 	if typ == nil {
 		// Unclear why gqlparser hasn't already rejected this,
 		// but empirically it might not.
-		return fmt.Errorf("undefined field %v", field.Alias())
+		return errorf(field.Pos(), "undefined field %v", field.Alias())
 	}
 
 	fields, err := field.SubFields()
@@ -291,7 +305,7 @@ func (builder *typeBuilder) writeType(namePrefix, nameOverride string, typ *ast.
 
 	def := builder.schema.Types[typ.Name()]
 	// Writes a typedef elsewhere (if not already defined)
-	name, err := builder.addTypeForDefinition(namePrefix, nameOverride, def, fields, options)
+	name, err := builder.addTypeForDefinition(namePrefix, nameOverride, def, typ.Position, fields, options)
 	if err != nil {
 		return err
 	}
@@ -300,7 +314,12 @@ func (builder *typeBuilder) writeType(namePrefix, nameOverride string, typ *ast.
 	return nil
 }
 
-func (builder *typeBuilder) writeTypedef(typedef *ast.Definition, fields []field, options *GenqlientDirective) error {
+func (builder *typeBuilder) writeTypedef(
+	typedef *ast.Definition,
+	pos *ast.Position,
+	fields []field,
+	options *GenqlientDirective,
+) error {
 	switch typedef.Kind {
 	case ast.Object, ast.InputObject:
 		builder.WriteString("struct {\n")
@@ -318,7 +337,7 @@ func (builder *typeBuilder) writeTypedef(typedef *ast.Definition, fields []field
 
 	case ast.Interface, ast.Union:
 		if !allowBrokenFeatures {
-			return fmt.Errorf("not implemented: %v", typedef.Kind)
+			return errorf(pos, "not implemented: %v", typedef.Kind)
 		}
 
 		// First, write the interface type.
@@ -332,7 +351,7 @@ func (builder *typeBuilder) writeTypedef(typedef *ast.Definition, fields []field
 		// Then, write the implementations.
 		// TODO(benkraft): Put a doc-comment somewhere with the list.
 		for _, impldef := range builder.schema.GetPossibleTypes(typedef) {
-			name, err := builder.addTypeForDefinition(builder.typeNamePrefix, "", impldef, fields, options)
+			name, err := builder.addTypeForDefinition(builder.typeNamePrefix, "", impldef, pos, fields, options)
 			if err != nil {
 				return err
 			}
@@ -355,8 +374,8 @@ func (builder *typeBuilder) writeTypedef(typedef *ast.Definition, fields []field
 		builder.WriteString(")\n")
 		return nil
 	case ast.Scalar:
-		return fmt.Errorf("unknown scalar %v: please add it to genqlient.yaml", typedef.Name)
+		return errorf(pos, "unknown scalar %v: please add it to genqlient.yaml", typedef.Name)
 	default:
-		return fmt.Errorf("unexpected kind: %v", typedef.Kind)
+		return errorf(pos, "unexpected kind: %v", typedef.Kind)
 	}
 }