ref: 10dc87bf866f7a4f99c248436c38edf0ecdd157f
dir: /tpl/tplimpl/template_ast_transformers.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 (
"errors"
"html/template"
"strings"
texttemplate "text/template"
"text/template/parse"
)
// decl keeps track of the variable mappings, i.e. $mysite => .Site etc.
type decl map[string]string
const (
paramsIdentifier = "Params"
)
// Containers that may contain Params that we will not touch.
var reservedContainers = map[string]bool{
// Aka .Site.Data.Params which must stay case sensitive.
"Data": true,
}
type templateContext struct {
decl decl
visited map[string]bool
lookupFn func(name string) *parse.Tree
}
func (c templateContext) getIfNotVisited(name string) *parse.Tree {
if c.visited[name] {
return nil
}
c.visited[name] = true
return c.lookupFn(name)
}
func newTemplateContext(lookupFn func(name string) *parse.Tree) *templateContext {
return &templateContext{lookupFn: lookupFn, decl: make(map[string]string), visited: make(map[string]bool)}
}
func createParseTreeLookup(templ *template.Template) func(nn string) *parse.Tree {
return func(nn string) *parse.Tree {
tt := templ.Lookup(nn)
if tt != nil {
return tt.Tree
}
return nil
}
}
func applyTemplateTransformersToHMLTTemplate(templ *template.Template) error {
return applyTemplateTransformers(templ.Tree, createParseTreeLookup(templ))
}
func applyTemplateTransformersToTextTemplate(templ *texttemplate.Template) error {
return applyTemplateTransformers(templ.Tree,
func(nn string) *parse.Tree {
tt := templ.Lookup(nn)
if tt != nil {
return tt.Tree
}
return nil
})
}
func applyTemplateTransformers(templ *parse.Tree, lookupFn func(name string) *parse.Tree) error {
if templ == nil {
return errors.New("expected template, but none provided")
}
c := newTemplateContext(lookupFn)
c.paramsKeysToLower(templ.Root)
return nil
}
// paramsKeysToLower is made purposely non-generic to make it not so tempting
// to do more of these hard-to-maintain AST transformations.
func (c *templateContext) paramsKeysToLower(n parse.Node) {
switch x := n.(type) {
case *parse.ListNode:
if x != nil {
c.paramsKeysToLowerForNodes(x.Nodes...)
}
case *parse.ActionNode:
c.paramsKeysToLowerForNodes(x.Pipe)
case *parse.IfNode:
c.paramsKeysToLowerForNodes(x.Pipe, x.List, x.ElseList)
case *parse.WithNode:
c.paramsKeysToLowerForNodes(x.Pipe, x.List, x.ElseList)
case *parse.RangeNode:
c.paramsKeysToLowerForNodes(x.Pipe, x.List, x.ElseList)
case *parse.TemplateNode:
subTempl := c.getIfNotVisited(x.Name)
if subTempl != nil {
c.paramsKeysToLowerForNodes(subTempl.Root)
}
case *parse.PipeNode:
for i, elem := range x.Decl {
if len(x.Cmds) > i {
// maps $site => .Site etc.
c.decl[elem.Ident[0]] = x.Cmds[i].String()
}
}
for _, cmd := range x.Cmds {
c.paramsKeysToLower(cmd)
}
case *parse.CommandNode:
for _, elem := range x.Args {
switch an := elem.(type) {
case *parse.FieldNode:
c.updateIdentsIfNeeded(an.Ident)
case *parse.VariableNode:
c.updateIdentsIfNeeded(an.Ident)
case *parse.PipeNode:
c.paramsKeysToLower(an)
}
}
}
}
func (c *templateContext) paramsKeysToLowerForNodes(nodes ...parse.Node) {
for _, node := range nodes {
c.paramsKeysToLower(node)
}
}
func (c *templateContext) updateIdentsIfNeeded(idents []string) {
index := c.decl.indexOfReplacementStart(idents)
if index == -1 {
return
}
for i := index; i < len(idents); i++ {
idents[i] = strings.ToLower(idents[i])
}
}
// indexOfReplacementStart will return the index of where to start doing replacement,
// -1 if none needed.
func (d decl) indexOfReplacementStart(idents []string) int {
l := len(idents)
if l == 0 {
return -1
}
if l == 1 {
first := idents[0]
if first == "" || first == paramsIdentifier || first[0] == '$' {
// This can not be a Params.x
return -1
}
}
var lookFurther bool
var needsVarExpansion bool
for _, ident := range idents {
if ident[0] == '$' {
lookFurther = true
needsVarExpansion = true
break
} else if ident == paramsIdentifier {
lookFurther = true
break
}
}
if !lookFurther {
return -1
}
var resolvedIdents []string
if !needsVarExpansion {
resolvedIdents = idents
} else {
var ok bool
resolvedIdents, ok = d.resolveVariables(idents)
if !ok {
return -1
}
}
var paramFound bool
for i, ident := range resolvedIdents {
if ident == paramsIdentifier {
if i > 0 {
container := resolvedIdents[i-1]
if reservedContainers[container] {
// .Data.Params.someKey
return -1
}
}
paramFound = true
break
}
}
if !paramFound {
return -1
}
var paramSeen bool
idx := -1
for i, ident := range idents {
if ident == "" || ident[0] == '$' {
continue
}
if ident == paramsIdentifier {
paramSeen = true
idx = -1
} else {
if paramSeen {
return i
}
if idx == -1 {
idx = i
}
}
}
return idx
}
func (d decl) resolveVariables(idents []string) ([]string, bool) {
var (
replacements []string
replaced []string
)
// An Ident can start out as one of
// [Params] [$blue] [$colors.Blue]
// We need to resolve the variables, so
// $blue => [Params Colors Blue]
// etc.
replacements = []string{idents[0]}
// Loop until there are no more $vars to resolve.
for i := 0; i < len(replacements); i++ {
if i > 20 {
// bail out
return nil, false
}
potentialVar := replacements[i]
if potentialVar == "$" {
continue
}
if potentialVar == "" || potentialVar[0] != '$' {
// leave it as is
replaced = append(replaced, strings.Split(potentialVar, ".")...)
continue
}
replacement, ok := d[potentialVar]
if !ok {
// Temporary range vars. We do not care about those.
return nil, false
}
if !d.isKeyword(replacement) {
// This can not be .Site.Params etc.
return nil, false
}
replacement = strings.TrimPrefix(replacement, ".")
if replacement == "" {
continue
}
if replacement[0] == '$' {
// Needs further expansion
replacements = append(replacements, strings.Split(replacement, ".")...)
} else {
replaced = append(replaced, strings.Split(replacement, ".")...)
}
}
return append(replaced, idents[1:]...), true
}
func (d decl) isKeyword(s string) bool {
return !strings.ContainsAny(s, " -\"")
}