hugo/tpl/tplimpl/template_ast_transformers.go
Paul Gottschling 5758c370ea
Allow for return partials with falsy arguments (#9298)
Partials with returns values are parsed, then inserted into a
partial return wrapper via wrapInPartialReturnWrapper in order
to assign the return value via *contextWrapper.Set. The
predefined wrapper template for partials inserts a partial's nodes
into a "with" template action in order to set dot to a
*contextWrapper within the partial. However, because "with" is
skipped if its argument is falsy, partials with falsy arguments
were not being evaluated.

This replaces the "with" action in the partial wrapper with a
"range" action that isn't skipped if .Arg is falsy.

Fixes #7528
2021-12-17 08:35:21 +01:00

346 lines
8.6 KiB
Go

// Copyright 2016 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
// 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
// limitations under the License.
package tplimpl
import (
"regexp"
"strings"
htmltemplate "github.com/gohugoio/hugo/tpl/internal/go_templates/htmltemplate"
texttemplate "github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate"
"github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate/parse"
"github.com/gohugoio/hugo/common/maps"
"github.com/gohugoio/hugo/tpl"
"github.com/mitchellh/mapstructure"
"github.com/pkg/errors"
)
type templateType int
const (
templateUndefined templateType = iota
templateShortcode
templatePartial
)
type templateContext struct {
visited map[string]bool
templateNotFound map[string]bool
identityNotFound map[string]bool
lookupFn func(name string) *templateState
// The last error encountered.
err error
// Set when we're done checking for config header.
configChecked bool
t *templateState
// Store away the return node in partials.
returnNode *parse.CommandNode
}
func (c templateContext) getIfNotVisited(name string) *templateState {
if c.visited[name] {
return nil
}
c.visited[name] = true
templ := c.lookupFn(name)
if templ == nil {
// This may be a inline template defined outside of this file
// and not yet parsed. Unusual, but it happens.
// Store the name to try again later.
c.templateNotFound[name] = true
}
return templ
}
func newTemplateContext(
t *templateState,
lookupFn func(name string) *templateState) *templateContext {
return &templateContext{
t: t,
lookupFn: lookupFn,
visited: make(map[string]bool),
templateNotFound: make(map[string]bool),
identityNotFound: make(map[string]bool),
}
}
func applyTemplateTransformers(
t *templateState,
lookupFn func(name string) *templateState) (*templateContext, error) {
if t == nil {
return nil, errors.New("expected template, but none provided")
}
c := newTemplateContext(t, lookupFn)
tree := getParseTree(t.Template)
_, err := c.applyTransformations(tree.Root)
if err == nil && c.returnNode != nil {
// This is a partial with a return statement.
c.t.parseInfo.HasReturn = true
tree.Root = c.wrapInPartialReturnWrapper(tree.Root)
}
return c, err
}
func getParseTree(templ tpl.Template) *parse.Tree {
templ = unwrap(templ)
if text, ok := templ.(*texttemplate.Template); ok {
return text.Tree
}
return templ.(*htmltemplate.Template).Tree
}
const (
// We parse this template and modify the nodes in order to assign
// the return value of a partial to a contextWrapper via Set. We use
// "range" over a one-element slice so we can shift dot to the
// partial's argument, Arg, while allowing Arg to be falsy.
partialReturnWrapperTempl = `{{ $_hugo_dot := $ }}{{ $ := .Arg }}{{ range (slice .Arg) }}{{ $_hugo_dot.Set ("PLACEHOLDER") }}{{ end }}`
)
var partialReturnWrapper *parse.ListNode
func init() {
templ, err := texttemplate.New("").Parse(partialReturnWrapperTempl)
if err != nil {
panic(err)
}
partialReturnWrapper = templ.Tree.Root
}
// wrapInPartialReturnWrapper copies and modifies the parsed nodes of a
// predefined partial return wrapper to insert those of a user-defined partial.
func (c *templateContext) wrapInPartialReturnWrapper(n *parse.ListNode) *parse.ListNode {
wrapper := partialReturnWrapper.CopyList()
rangeNode := wrapper.Nodes[2].(*parse.RangeNode)
retn := rangeNode.List.Nodes[0]
setCmd := retn.(*parse.ActionNode).Pipe.Cmds[0]
setPipe := setCmd.Args[1].(*parse.PipeNode)
// Replace PLACEHOLDER with the real return value.
// Note that this is a PipeNode, so it will be wrapped in parens.
setPipe.Cmds = []*parse.CommandNode{c.returnNode}
rangeNode.List.Nodes = append(n.Nodes, retn)
return wrapper
}
// applyTransformations do 2 things:
// 1) Parses partial return statement.
// 2) Tracks template (partial) dependencies and some other info.
func (c *templateContext) applyTransformations(n parse.Node) (bool, error) {
switch x := n.(type) {
case *parse.ListNode:
if x != nil {
c.applyTransformationsToNodes(x.Nodes...)
}
case *parse.ActionNode:
c.applyTransformationsToNodes(x.Pipe)
case *parse.IfNode:
c.applyTransformationsToNodes(x.Pipe, x.List, x.ElseList)
case *parse.WithNode:
c.applyTransformationsToNodes(x.Pipe, x.List, x.ElseList)
case *parse.RangeNode:
c.applyTransformationsToNodes(x.Pipe, x.List, x.ElseList)
case *parse.TemplateNode:
subTempl := c.getIfNotVisited(x.Name)
if subTempl != nil {
c.applyTransformationsToNodes(getParseTree(subTempl.Template).Root)
}
case *parse.PipeNode:
c.collectConfig(x)
for i, cmd := range x.Cmds {
keep, _ := c.applyTransformations(cmd)
if !keep {
x.Cmds = append(x.Cmds[:i], x.Cmds[i+1:]...)
}
}
case *parse.CommandNode:
c.collectPartialInfo(x)
c.collectInner(x)
keep := c.collectReturnNode(x)
for _, elem := range x.Args {
switch an := elem.(type) {
case *parse.PipeNode:
c.applyTransformations(an)
}
}
return keep, c.err
}
return true, c.err
}
func (c *templateContext) applyTransformationsToNodes(nodes ...parse.Node) {
for _, node := range nodes {
c.applyTransformations(node)
}
}
func (c *templateContext) hasIdent(idents []string, ident string) bool {
for _, id := range idents {
if id == ident {
return true
}
}
return false
}
// collectConfig collects and parses any leading template config variable declaration.
// This will be the first PipeNode in the template, and will be a variable declaration
// on the form:
// {{ $_hugo_config:= `{ "version": 1 }` }}
func (c *templateContext) collectConfig(n *parse.PipeNode) {
if c.t.typ != templateShortcode {
return
}
if c.configChecked {
return
}
c.configChecked = true
if len(n.Decl) != 1 || len(n.Cmds) != 1 {
// This cannot be a config declaration
return
}
v := n.Decl[0]
if len(v.Ident) == 0 || v.Ident[0] != "$_hugo_config" {
return
}
cmd := n.Cmds[0]
if len(cmd.Args) == 0 {
return
}
if s, ok := cmd.Args[0].(*parse.StringNode); ok {
errMsg := "failed to decode $_hugo_config in template"
m, err := maps.ToStringMapE(s.Text)
if err != nil {
c.err = errors.Wrap(err, errMsg)
return
}
if err := mapstructure.WeakDecode(m, &c.t.parseInfo.Config); err != nil {
c.err = errors.Wrap(err, errMsg)
}
}
}
// collectInner determines if the given CommandNode represents a
// shortcode call to its .Inner.
func (c *templateContext) collectInner(n *parse.CommandNode) {
if c.t.typ != templateShortcode {
return
}
if c.t.parseInfo.IsInner || len(n.Args) == 0 {
return
}
for _, arg := range n.Args {
var idents []string
switch nt := arg.(type) {
case *parse.FieldNode:
idents = nt.Ident
case *parse.VariableNode:
idents = nt.Ident
}
if c.hasIdent(idents, "Inner") {
c.t.parseInfo.IsInner = true
break
}
}
}
var partialRe = regexp.MustCompile(`^partial(Cached)?$|^partials\.Include(Cached)?$`)
func (c *templateContext) collectPartialInfo(x *parse.CommandNode) {
if len(x.Args) < 2 {
return
}
first := x.Args[0]
var id string
switch v := first.(type) {
case *parse.IdentifierNode:
id = v.Ident
case *parse.ChainNode:
id = v.String()
}
if partialRe.MatchString(id) {
partialName := strings.Trim(x.Args[1].String(), "\"")
if !strings.Contains(partialName, ".") {
partialName += ".html"
}
partialName = "partials/" + partialName
info := c.lookupFn(partialName)
if info != nil {
c.t.Add(info)
} else {
// Delay for later
c.identityNotFound[partialName] = true
}
}
}
func (c *templateContext) collectReturnNode(n *parse.CommandNode) bool {
if c.t.typ != templatePartial || c.returnNode != nil {
return true
}
if len(n.Args) < 2 {
return true
}
ident, ok := n.Args[0].(*parse.IdentifierNode)
if !ok || ident.Ident != "return" {
return true
}
c.returnNode = n
// Remove the "return" identifiers
c.returnNode.Args = c.returnNode.Args[1:]
return false
}
func findTemplateIn(name string, in tpl.Template) (tpl.Template, bool) {
in = unwrap(in)
if text, ok := in.(*texttemplate.Template); ok {
if templ := text.Lookup(name); templ != nil {
return templ, true
}
return nil, false
}
if templ := in.(*htmltemplate.Template).Lookup(name); templ != nil {
return templ, true
}
return nil, false
}