salix/tags.go

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/*
* Salix - Go templating engine
* Copyright (C) 2023 Elara Musayelyan
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
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package salix
import (
"bytes"
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"io"
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"go.elara.ws/salix/ast"
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)
// Tag represents a tag in a Salix template
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type Tag interface {
Run(tc *TagContext, block, args []ast.Node) error
}
var globalTags = map[string]Tag{
"if": ifTag{},
"for": forTag{},
"include": includeTag{},
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"macro": macroTag{},
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}
// TagContext is passed to Tag implementations to allow them to control the interpreter
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type TagContext struct {
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Tag ast.Tag
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w io.Writer
t *Template
local map[string]any
}
// Execute runs the interpreter on the given AST nodes, with the given local variables.
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func (tc *TagContext) Execute(nodes []ast.Node, local map[string]any) error {
return tc.t.execute(tc.w, nodes, mergeMap(tc.local, local))
}
// ExecuteToMemory runs the interpreter on the given AST nodes, with the given local variables, and
// returns the resulting bytes rather than writing them out.
func (tc *TagContext) ExecuteToMemory(nodes []ast.Node, local map[string]any) ([]byte, error) {
buf := &bytes.Buffer{}
err := tc.t.execute(buf, nodes, mergeMap(tc.local, local))
if err != nil {
return nil, err
}
return buf.Bytes(), nil
}
// GetValue evaluates the given AST node using the given local variables.
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func (tc *TagContext) GetValue(node ast.Node, local map[string]any) (any, error) {
return tc.t.getValue(node, mergeMap(tc.local, local))
}
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// PosError returns an error with the file position prepended. This should be used
// for errors wherever possible, to make it easier for users to find errors.
func (tc *TagContext) PosError(node ast.Node, format string, v ...any) error {
return ast.PosError(node, format, v...)
}
// NodeToString returns a textual representation of the given AST node for users to see,
// such as in error messages. This does not directly correlate to Salix source code.
func (tc *TagContext) NodeToString(node ast.Node) string {
return valueToString(node)
}
// Write writes b to the underlying writer. It implements
// the io.Writer interface.
func (tc *TagContext) Write(b []byte) (int, error) {
return tc.w.Write(b)
}
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func mergeMap(a, b map[string]any) map[string]any {
out := map[string]any{}
if a != nil {
for k, v := range a {
out[k] = v
}
}
if b != nil {
for k, v := range b {
out[k] = v
}
}
return out
}