package parse

import (

"encoding/json"

"strings"

"github.com/moby/buildkit/frontend/dockerfile/parser"

)

func parseSHELL(node *parser.Node) []Rule {

if node.Next == nil {

return []Rule{invalidInstructionRule(node, "SHELL requires at least one argument")}

}

// ERROR CHECKS - Return immediately on first error

// Extract shell configuration

shellConfig := extractSHELLConfig(node)

// Validate that config is not empty

if strings.TrimSpace(shellConfig) == "" {

return []Rule{NewErrorRule(node, "ShellMissingConfig",

"SHELL instruction must specify a shell configuration",

"https://docs.docker.com/reference/dockerfile/#shell")}

}

// SHELL instruction MUST be in JSON form

if !strings.HasPrefix(strings.TrimSpace(shellConfig), "[") {

return []Rule{NewErrorRule(node, "ShellRequiresJsonForm",

"SHELL instruction must be written in JSON form (e.g., SHELL [\"executable\", \"parameters\"])",

"https://docs.docker.com/reference/dockerfile/#shell")}

}

// Validate JSON form

if !checkSHELLJsonForm(shellConfig) {

return []Rule{NewErrorRule(node, "ShellInvalidJsonForm",

"SHELL instruction must be a valid JSON array with double quotes",

"https://docs.docker.com/reference/dockerfile/#shell")}

}

// No warnings in this file

return nil

}

// extractSHELLConfig extracts the shell configuration from the SHELL instruction

func extractSHELLConfig(node *parser.Node) string {

if node.Next == nil {

return ""

}

// Use the Original field and strip the instruction keyword

// This preserves the exact format including key=value pairs

config := strings.TrimPrefix(node.Original, node.Value)

return strings.TrimSpace(config)

}

// checkSHELLJsonForm validates that the SHELL instruction is valid JSON array

func checkSHELLJsonForm(config string) bool {

config = strings.TrimSpace(config)

// Must start with '[' and end with ']'

if !strings.HasPrefix(config, "[") || !strings.HasSuffix(config, "]") {

return false

}

// Try to parse as JSON array

var arr []string

if err := json.Unmarshal([]byte(config), &arr); err != nil {

return false

}

// Array should not be empty

if len(arr) == 0 {

return false

}

// Check that original string uses double quotes, not single quotes

// Single quotes are not valid JSON

if strings.Contains(config, "['") || strings.Contains(config, "']") {

return false

}

return true

}