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text/template, html/template: add block keyword and permit template redefinition

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This change adds a new "block" keyword that permits the definition
of templates inline inside existing templates, and loosens the
restriction on template redefinition. Templates may now be redefined,
but in the html/template package they may only be redefined before
the template is executed (and therefore escaped).

The intention is that such inline templates can be redefined by
subsequent template definitions, permitting a kind of template
"inheritance" or "overlay". (See the example for details.)

Fixes #3812

Change-Id: I733cb5332c1c201c235f759cc64333462e70dc27
Reviewed-on: https://go-review.googlesource.com/14005
Reviewed-by: Rob Pike <r@golang.org>
This commit is contained in:
Andrew Gerrand 2015-08-28 15:31:51 +10:00
parent 09c6d13ac2
commit 12dfc3bee4
12 changed files with 239 additions and 72 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
src/html/template/clone_test.go
View File

@ -78,9 +78,17 @@ func TestClone(t *testing.T) {
Must(t0.Parse(`{{define "lhs"}} ( {{end}}`))
Must(t0.Parse(`{{define "rhs"}} ) {{end}}`))
// Clone t0 as t4. Redefining the "lhs" template should fail.
// Clone t0 as t4. Redefining the "lhs" template should not fail.
t4 := Must(t0.Clone())
if _, err := t4.Parse(`{{define "lhs"}} FAIL {{end}}`); err == nil {
if _, err := t4.Parse(`{{define "lhs"}} OK {{end}}`); err != nil {
t.Error(`redefine "lhs": got err %v want non-nil`, err)
}
// Cloning t1 should fail as it has been executed.
if _, err := t1.Clone(); err == nil {
t.Error("cloning t1: got nil err want non-nil")
}
// Redefining the "lhs" template in t1 should fail as it has been executed.
if _, err := t1.Parse(`{{define "lhs"}} OK {{end}}`); err == nil {
t.Error(`redefine "lhs": got nil err want non-nil`)
}

36
src/html/template/example_test.go
View File

@ -9,6 +9,7 @@ import (
"html/template"
"log"
"os"
"strings"
)
func Example() {
@ -120,3 +121,38 @@ func Example_escape() {
// %22Fran+%26+Freddie%27s+Diner%2232%3Ctasty%40example.com%3E
}
// The following example is duplicated in text/template; keep them in sync.
func ExampleBlock() {
const (
master = `Names:{{block "list" .}}{{"\n"}}{{range .}}{{println "-" .}}{{end}}{{end}}`
overlay = `{{define "list"}} {{join . ", "}}{{end}} `
)
var (
funcs = template.FuncMap{"join": strings.Join}
guardians = []string{"Gamora", "Groot", "Nebula", "Rocket", "Star-Lord"}
)
masterTmpl, err := template.New("master").Funcs(funcs).Parse(master)
if err != nil {
log.Fatal(err)
}
overlayTmpl, err := template.Must(masterTmpl.Clone()).Parse(overlay)
if err != nil {
log.Fatal(err)
}
if err := masterTmpl.Execute(os.Stdout, guardians); err != nil {
log.Fatal(err)
}
if err := overlayTmpl.Execute(os.Stdout, guardians); err != nil {
log.Fatal(err)
}
// Output:
// Names:
// - Gamora
// - Groot
// - Nebula
// - Rocket
// - Star-Lord
// Names: Gamora, Groot, Nebula, Rocket, Star-Lord
}

4
src/html/template/template.go
View File

@ -18,7 +18,7 @@ import (
// Template is a specialized Template from "text/template" that produces a safe
// HTML document fragment.
type Template struct {
// Sticky error if escaping fails.
// Sticky error if escaping fails, or escapeOK if succeeded.
escapeErr error
// We could embed the text/template field, but it's safer not to because
// we need to keep our version of the name space and the underlying
@ -170,6 +170,8 @@ func (t *Template) Parse(src string) (*Template, error) {
tmpl := t.set[name]
if tmpl == nil {
tmpl = t.new(name)
} else if tmpl.escapeErr != nil {
return nil, fmt.Errorf("html/template: cannot redefine %q after it has executed", name)
}
// Restore our record of this text/template to its unescaped original state.
tmpl.escapeErr = nil

8
src/text/template/doc.go
View File

@ -115,6 +115,14 @@ data, defined in detail below.
The template with the specified name is executed with dot set
to the value of the pipeline.
{{block "name" pipeline}} T1 {{end}}
A block is shorthand for defining a template
{{define "name"}} T1 {{end}}
and then executing it in place
{{template "name" .}}
The typical use is to define a set of root templates that are
then customized by redefining the block templates within.
{{with pipeline}} T1 {{end}}
If the value of the pipeline is empty, no output is generated;
otherwise, dot is set to the value of the pipeline and T1 is

36
src/text/template/example_test.go
View File

@ -7,6 +7,7 @@ package template_test
import (
"log"
"os"
"strings"
"text/template"
)
@ -72,3 +73,38 @@ Josie
// Best wishes,
// Josie
}
// The following example is duplicated in html/template; keep them in sync.
func ExampleBlock() {
const (
master = `Names:{{block "list" .}}{{"\n"}}{{range .}}{{println "-" .}}{{end}}{{end}}`
overlay = `{{define "list"}} {{join . ", "}}{{end}} `
)
var (
funcs = template.FuncMap{"join": strings.Join}
guardians = []string{"Gamora", "Groot", "Nebula", "Rocket", "Star-Lord"}
)
masterTmpl, err := template.New("master").Funcs(funcs).Parse(master)
if err != nil {
log.Fatal(err)
}
overlayTmpl, err := template.Must(masterTmpl.Clone()).Parse(overlay)
if err != nil {
log.Fatal(err)
}
if err := masterTmpl.Execute(os.Stdout, guardians); err != nil {
log.Fatal(err)
}
if err := overlayTmpl.Execute(os.Stdout, guardians); err != nil {
log.Fatal(err)
}
// Output:
// Names:
// - Gamora
// - Groot
// - Nebula
// - Rocket
// - Star-Lord
// Names: Gamora, Groot, Nebula, Rocket, Star-Lord
}

33
src/text/template/exec_test.go
View File

@ -1232,3 +1232,36 @@ func testBadFuncName(name string, t *testing.T) {
// reports an error.
t.Errorf("%q succeeded incorrectly as function name", name)
}
func TestBlock(t *testing.T) {
const (
input = `a({{block "inner" .}}bar({{.}})baz{{end}})b`
want = `a(bar(hello)baz)b`
overlay = `{{define "inner"}}foo({{.}})bar{{end}}`
want2 = `a(foo(goodbye)bar)b`
)
tmpl, err := New("outer").Parse(input)
if err != nil {
t.Fatal(err)
}
tmpl2, err := Must(tmpl.Clone()).Parse(overlay)
if err != nil {
t.Fatal(err)
}
var buf bytes.Buffer
if err := tmpl.Execute(&buf, "hello"); err != nil {
t.Fatal(err)
}
if got := buf.String(); got != want {
t.Errorf("got %q, want %q", got, want)
}
buf.Reset()
if err := tmpl2.Execute(&buf, "goodbye"); err != nil {
t.Fatal(err)
}
if got := buf.String(); got != want2 {
t.Errorf("got %q, want %q", got, want2)
}
}

22
src/text/template/multi_test.go
View File

@ -9,7 +9,6 @@ package template
import (
"bytes"
"fmt"
"strings"
"testing"
"text/template/parse"
)
@ -277,17 +276,11 @@ func TestRedefinition(t *testing.T) {
if tmpl, err = New("tmpl1").Parse(`{{define "test"}}foo{{end}}`); err != nil {
t.Fatalf("parse 1: %v", err)
}
if _, err = tmpl.Parse(`{{define "test"}}bar{{end}}`); err == nil {
t.Fatal("expected error")
if _, err = tmpl.Parse(`{{define "test"}}bar{{end}}`); err != nil {
t.Fatal("got error %v, expected nil", err)
}
if !strings.Contains(err.Error(), "redefinition") {
t.Fatalf("expected redefinition error; got %v", err)
}
if _, err = tmpl.New("tmpl2").Parse(`{{define "test"}}bar{{end}}`); err == nil {
t.Fatal("expected error")
}
if !strings.Contains(err.Error(), "redefinition") {
t.Fatalf("expected redefinition error; got %v", err)
if _, err = tmpl.New("tmpl2").Parse(`{{define "test"}}bar{{end}}`); err != nil {
t.Fatal("got error %v, expected nil", err)
}
}
@ -345,7 +338,6 @@ func TestNew(t *testing.T) {
func TestParse(t *testing.T) {
// In multiple calls to Parse with the same receiver template, only one call
// can contain text other than space, comments, and template definitions
var err error
t1 := New("test")
if _, err := t1.Parse(`{{define "test"}}{{end}}`); err != nil {
t.Fatalf("parsing test: %s", err)
@ -356,10 +348,4 @@ func TestParse(t *testing.T) {
if _, err := t1.Parse(`{{define "test"}}foo{{end}}`); err != nil {
t.Fatalf("parsing test: %s", err)
}
if _, err = t1.Parse(`{{define "test"}}foo{{end}}`); err == nil {
t.Fatal("no error from redefining a template")
}
if !strings.Contains(err.Error(), "redefinition") {
t.Fatalf("expected redefinition error; got %v", err)
}
}

2
src/text/template/parse/lex.go
View File

@ -58,6 +58,7 @@ const (
itemVariable // variable starting with '$', such as '$' or '$1' or '$hello'
// Keywords appear after all the rest.
itemKeyword // used only to delimit the keywords
itemBlock // block keyword
itemDot // the cursor, spelled '.'
itemDefine // define keyword
itemElse // else keyword
@ -71,6 +72,7 @@ const (
var key = map[string]itemType{
".": itemDot,
"block": itemBlock,
"define": itemDefine,
"else": itemElse,
"end": itemEnd,

16
src/text/template/parse/lex_test.go
View File

@ -33,6 +33,7 @@ var itemName = map[itemType]string{
// keywords
itemDot: ".",
itemBlock: "block",
itemDefine: "define",
itemElse: "else",
itemIf: "if",
@ -58,6 +59,8 @@ type lexTest struct {
}
var (
tDot = item{itemDot, 0, "."}
tBlock = item{itemBlock, 0, "block"}
tEOF = item{itemEOF, 0, ""}
tFor = item{itemIdentifier, 0, "for"}
tLeft = item{itemLeftDelim, 0, "{{"}
@ -104,6 +107,9 @@ var lexTests = []lexTest{
}},
{"empty action", `{{}}`, []item{tLeft, tRight, tEOF}},
{"for", `{{for}}`, []item{tLeft, tFor, tRight, tEOF}},
{"block", `{{block "foo" .}}`, []item{
tLeft, tBlock, tSpace, {itemString, 0, `"foo"`}, tSpace, tDot, tRight, tEOF,
}},
{"quote", `{{"abc \n\t\" "}}`, []item{tLeft, tQuote, tRight, tEOF}},
{"raw quote", "{{" + raw + "}}", []item{tLeft, tRawQuote, tRight, tEOF}},
{"raw quote with newline", "{{" + rawNL + "}}", []item{tLeft, tRawQuoteNL, tRight, tEOF}},
@ -155,7 +161,7 @@ var lexTests = []lexTest{
}},
{"dot", "{{.}}", []item{
tLeft,
{itemDot, 0, "."},
tDot,
tRight,
tEOF,
}},
@ -169,7 +175,7 @@ var lexTests = []lexTest{
tLeft,
{itemField, 0, ".x"},
tSpace,
{itemDot, 0, "."},
tDot,
tSpace,
{itemNumber, 0, ".2"},
tSpace,
@ -501,9 +507,9 @@ func TestShutdown(t *testing.T) {
func (t *Tree) parseLexer(lex *lexer, text string) (tree *Tree, err error) {
defer t.recover(&err)
t.ParseName = t.Name
t.startParse(nil, lex)
t.parse(nil)
t.add(nil)
t.startParse(nil, lex, map[string]*Tree{})
t.parse()
t.add()
t.stopParse()
return t, nil
}

83
src/text/template/parse/parse.go
View File

@ -28,6 +28,7 @@ type Tree struct {
token [3]item // three-token lookahead for parser.
peekCount int
vars []string // variables defined at the moment.
treeSet map[string]*Tree
}
// Copy returns a copy of the Tree. Any parsing state is discarded.
@ -205,11 +206,12 @@ func (t *Tree) recover(errp *error) {
}
// startParse initializes the parser, using the lexer.
func (t *Tree) startParse(funcs []map[string]interface{}, lex *lexer) {
func (t *Tree) startParse(funcs []map[string]interface{}, lex *lexer, treeSet map[string]*Tree) {
t.Root = nil
t.lex = lex
t.vars = []string{"$"}
t.funcs = funcs
t.treeSet = treeSet
}
// stopParse terminates parsing.
@ -217,6 +219,7 @@ func (t *Tree) stopParse() {
t.lex = nil
t.vars = nil
t.funcs = nil
t.treeSet = nil
}
// Parse parses the template definition string to construct a representation of
@ -226,19 +229,19 @@ func (t *Tree) stopParse() {
func (t *Tree) Parse(text, leftDelim, rightDelim string, treeSet map[string]*Tree, funcs ...map[string]interface{}) (tree *Tree, err error) {
defer t.recover(&err)
t.ParseName = t.Name
t.startParse(funcs, lex(t.Name, text, leftDelim, rightDelim))
t.startParse(funcs, lex(t.Name, text, leftDelim, rightDelim), treeSet)
t.text = text
t.parse(treeSet)
t.add(treeSet)
t.parse()
t.add()
t.stopParse()
return t, nil
}
// add adds tree to the treeSet.
func (t *Tree) add(treeSet map[string]*Tree) {
tree := treeSet[t.Name]
// add adds tree to t.treeSet.
func (t *Tree) add() {
tree := t.treeSet[t.Name]
if tree == nil || IsEmptyTree(tree.Root) {
treeSet[t.Name] = t
t.treeSet[t.Name] = t
return
}
if !IsEmptyTree(t.Root) {
@ -274,7 +277,7 @@ func IsEmptyTree(n Node) bool {
// parse is the top-level parser for a template, essentially the same
// as itemList except it also parses {{define}} actions.
// It runs to EOF.
func (t *Tree) parse(treeSet map[string]*Tree) (next Node) {
func (t *Tree) parse() (next Node) {
t.Root = t.newList(t.peek().pos)
for t.peek().typ != itemEOF {
if t.peek().typ == itemLeftDelim {
@ -283,8 +286,8 @@ func (t *Tree) parse(treeSet map[string]*Tree) (next Node) {
newT := New("definition") // name will be updated once we know it.
newT.text = t.text
newT.ParseName = t.ParseName
newT.startParse(t.funcs, t.lex)
newT.parseDefinition(treeSet)
newT.startParse(t.funcs, t.lex, t.treeSet)
newT.parseDefinition()
continue
}
t.backup2(delim)
@ -300,9 +303,9 @@ func (t *Tree) parse(treeSet map[string]*Tree) (next Node) {
}
// parseDefinition parses a {{define}} ... {{end}} template definition and
// installs the definition in the treeSet map. The "define" keyword has already
// installs the definition in t.treeSet. The "define" keyword has already
// been scanned.
func (t *Tree) parseDefinition(treeSet map[string]*Tree) {
func (t *Tree) parseDefinition() {
const context = "define clause"
name := t.expectOneOf(itemString, itemRawString, context)
var err error
@ -316,7 +319,7 @@ func (t *Tree) parseDefinition(treeSet map[string]*Tree) {
if end.Type() != nodeEnd {
t.errorf("unexpected %s in %s", end, context)
}
t.add(treeSet)
t.add()
t.stopParse()
}
@ -358,6 +361,8 @@ func (t *Tree) textOrAction() Node {
// First word could be a keyword such as range.
func (t *Tree) action() (n Node) {
switch token := t.nextNonSpace(); token.typ {
case itemBlock:
return t.blockControl()
case itemElse:
return t.elseControl()
case itemEnd:
@ -522,13 +527,51 @@ func (t *Tree) elseControl() Node {
return t.newElse(t.expect(itemRightDelim, "else").pos, t.lex.lineNumber())
}
// Block:
// {{block stringValue pipeline}}
// Block keyword is past.
// The name must be something that can evaluate to a string.
// The pipeline is mandatory.
func (t *Tree) blockControl() Node {
const context = "block clause"
token := t.nextNonSpace()
name := t.parseTemplateName(token, context)
pipe := t.pipeline(context)
block := New(name) // name will be updated once we know it.
block.text = t.text
block.ParseName = t.ParseName
block.startParse(t.funcs, t.lex, t.treeSet)
var end Node
block.Root, end = block.itemList()
if end.Type() != nodeEnd {
t.errorf("unexpected %s in %s", end, context)
}
block.add()
block.stopParse()
return t.newTemplate(token.pos, t.lex.lineNumber(), name, pipe)
}
// Template:
// {{template stringValue pipeline}}
// Template keyword is past. The name must be something that can evaluate
// to a string.
func (t *Tree) templateControl() Node {
var name string
const context = "template clause"
token := t.nextNonSpace()
name := t.parseTemplateName(token, context)
var pipe *PipeNode
if t.nextNonSpace().typ != itemRightDelim {
t.backup()
// Do not pop variables; they persist until "end".
pipe = t.pipeline(context)
}
return t.newTemplate(token.pos, t.lex.lineNumber(), name, pipe)
}
func (t *Tree) parseTemplateName(token item, context string) (name string) {
switch token.typ {
case itemString, itemRawString:
s, err := strconv.Unquote(token.val)
@ -537,15 +580,9 @@ func (t *Tree) templateControl() Node {
}
name = s
default:
t.unexpected(token, "template invocation")
t.unexpected(token, context)
}
var pipe *PipeNode
if t.nextNonSpace().typ != itemRightDelim {
t.backup()
// Do not pop variables; they persist until "end".
pipe = t.pipeline("template")
}
return t.newTemplate(token.pos, t.lex.lineNumber(), name, pipe)
return
}
// command:

27
src/text/template/parse/parse_test.go
View File

@ -235,6 +235,8 @@ var parseTests = []parseTest{
{"comment trim left", "x \r\n\t{{- /* hi */}}", noError, `"x"`},
{"comment trim right", "{{/* hi */ -}}\n\n\ty", noError, `"y"`},
{"comment trim left and right", "x \r\n\t{{- /* */ -}}\n\n\ty", noError, `"x""y"`},
{"block definition", `{{block "foo" .}}hello{{end}}`, noError,
`{{template "foo" .}}`},
// Errors.
{"unclosed action", "hello{{range", hasError, ""},
{"unmatched end", "{{end}}", hasError, ""},
@ -284,6 +286,8 @@ var parseTests = []parseTest{
{"wrong pipeline boolean", "{{.|true}}", hasError, ""},
{"wrong pipeline nil", "{{'c'|nil}}", hasError, ""},
{"empty pipeline", `{{printf "%d" ( ) }}`, hasError, ""},
// Missing pipeline in block
{"block definition", `{{block "foo"}}hello{{end}}`, hasError, ""},
}
var builtins = map[string]interface{}{
@ -457,3 +461,26 @@ func TestErrors(t *testing.T) {
}
}
}
func TestBlock(t *testing.T) {
const (
input = `a{{block "inner" .}}bar{{.}}baz{{end}}b`
outer = `a{{template "inner" .}}b`
inner = `bar{{.}}baz`
)
treeSet := make(map[string]*Tree)
tmpl, err := New("outer").Parse(input, "", "", treeSet, nil)
if err != nil {
t.Fatal(err)
}
if g, w := tmpl.Root.String(), outer; g != w {
t.Errorf("outer template = %q, want %q", g, w)
}
inTmpl := treeSet["inner"]
if inTmpl == nil {
t.Fatal("block did not define template")
}
if g, w := inTmpl.Root.String(), inner; g != w {
t.Errorf("inner template = %q, want %q", g, w)
}
}

32
src/text/template/template.go
View File

@ -5,7 +5,6 @@
package template
import (
"fmt"
"reflect"
"sync"
"text/template/parse"
@ -117,11 +116,10 @@ func (t *Template) copy(c *common) *Template {
// AddParseTree adds parse tree for template with given name and associates it with t.
// If the template does not already exist, it will create a new one.
// It is an error to reuse a name except to overwrite an empty template.
// If the template does exist, it will be replaced.
func (t *Template) AddParseTree(name string, tree *parse.Tree) (*Template, error) {
t.init()
// If the name is the name of this template, overwrite this template.
// The associate method checks it's not a redefinition.
nt := t
if name != t.name {
nt = t.New(name)
@ -185,11 +183,7 @@ func (t *Template) Lookup(name string) *Template {
// Parse defines the template by parsing the text. Nested template definitions will be
// associated with the top-level template t. Parse may be called multiple times
// to parse definitions of templates to associate with t. It is an error if a
// resulting template is non-empty (contains content other than template
// definitions) and would replace a non-empty template with the same name.
// (In multiple calls to Parse with the same receiver template, only one call
// can contain text other than space, comments, and template definitions.)
// to parse definitions of templates to associate with t.
func (t *Template) Parse(text string) (*Template, error) {
t.init()
t.muFuncs.RLock()
@ -208,25 +202,17 @@ func (t *Template) Parse(text string) (*Template, error) {
}
// associate installs the new template into the group of templates associated
// with t. It is an error to reuse a name except to overwrite an empty
// template. The two are already known to share the common structure.
// The boolean return value reports wither to store this tree as t.Tree.
// with t. The two are already known to share the common structure.
// The boolean return value reports whether to store this tree as t.Tree.
func (t *Template) associate(new *Template, tree *parse.Tree) (bool, error) {
if new.common != t.common {
panic("internal error: associate not common")
}
name := new.name
if old := t.tmpl[name]; old != nil {
oldIsEmpty := parse.IsEmptyTree(old.Root)
newIsEmpty := parse.IsEmptyTree(tree.Root)
if newIsEmpty {
// Whether old is empty or not, new is empty; no reason to replace old.
return false, nil
}
if !oldIsEmpty {
return false, fmt.Errorf("template: redefinition of template %q", name)
}
if t.tmpl[new.name] != nil && parse.IsEmptyTree(tree.Root) {
// If a template by that name exists,
// don't replace it with an empty template.
return false, nil
}
t.tmpl[name] = new
t.tmpl[new.name] = new
return true, nil
}