216 lines
7.1 KiB
Go
216 lines
7.1 KiB
Go
// Package dockerfile is the evaluation step in the Dockerfile parse/evaluate pipeline.
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//
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// It incorporates a dispatch table based on the parser.Node values (see the
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// parser package for more information) that are yielded from the parser itself.
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// Calling NewBuilder with the BuildOpts struct can be used to customize the
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// experience for execution purposes only. Parsing is controlled in the parser
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// package, and this division of responsibility should be respected.
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//
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// Please see the jump table targets for the actual invocations, most of which
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// will call out to the functions in internals.go to deal with their tasks.
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//
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// ONBUILD is a special case, which is covered in the onbuild() func in
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// dispatchers.go.
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//
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// The evaluator uses the concept of "steps", which are usually each processable
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// line in the Dockerfile. Each step is numbered and certain actions are taken
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// before and after each step, such as creating an image ID and removing temporary
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// containers and images. Note that ONBUILD creates a kinda-sorta "sub run" which
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// includes its own set of steps (usually only one of them).
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package dockerfile
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import (
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"fmt"
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"runtime"
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"strings"
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"github.com/docker/docker/builder/dockerfile/command"
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"github.com/docker/docker/builder/dockerfile/parser"
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)
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// Environment variable interpolation will happen on these statements only.
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var replaceEnvAllowed = map[string]bool{
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command.Env: true,
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command.Label: true,
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command.Add: true,
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command.Copy: true,
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command.Workdir: true,
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command.Expose: true,
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command.Volume: true,
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command.User: true,
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command.StopSignal: true,
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command.Arg: true,
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}
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// Certain commands are allowed to have their args split into more
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// words after env var replacements. Meaning:
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// ENV foo="123 456"
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// EXPOSE $foo
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// should result in the same thing as:
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// EXPOSE 123 456
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// and not treat "123 456" as a single word.
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// Note that: EXPOSE "$foo" and EXPOSE $foo are not the same thing.
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// Quotes will cause it to still be treated as single word.
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var allowWordExpansion = map[string]bool{
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command.Expose: true,
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}
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var evaluateTable map[string]func(*Builder, []string, map[string]bool, string) error
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func init() {
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evaluateTable = map[string]func(*Builder, []string, map[string]bool, string) error{
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command.Env: env,
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command.Label: label,
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command.Maintainer: maintainer,
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command.Add: add,
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command.Copy: dispatchCopy, // copy() is a go builtin
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command.From: from,
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command.Onbuild: onbuild,
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command.Workdir: workdir,
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command.Run: run,
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command.Cmd: cmd,
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command.Entrypoint: entrypoint,
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command.Expose: expose,
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command.Volume: volume,
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command.User: user,
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command.StopSignal: stopSignal,
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command.Arg: arg,
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}
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}
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// This method is the entrypoint to all statement handling routines.
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//
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// Almost all nodes will have this structure:
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// Child[Node, Node, Node] where Child is from parser.Node.Children and each
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// node comes from parser.Node.Next. This forms a "line" with a statement and
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// arguments and we process them in this normalized form by hitting
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// evaluateTable with the leaf nodes of the command and the Builder object.
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//
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// ONBUILD is a special case; in this case the parser will emit:
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// Child[Node, Child[Node, Node...]] where the first node is the literal
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// "onbuild" and the child entrypoint is the command of the ONBUILD statement,
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// such as `RUN` in ONBUILD RUN foo. There is special case logic in here to
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// deal with that, at least until it becomes more of a general concern with new
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// features.
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func (b *Builder) dispatch(stepN int, ast *parser.Node) error {
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cmd := ast.Value
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upperCasedCmd := strings.ToUpper(cmd)
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// To ensure the user is given a decent error message if the platform
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// on which the daemon is running does not support a builder command.
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if err := platformSupports(strings.ToLower(cmd)); err != nil {
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return err
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}
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attrs := ast.Attributes
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original := ast.Original
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flags := ast.Flags
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strList := []string{}
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msg := fmt.Sprintf("Step %d : %s", stepN+1, upperCasedCmd)
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if len(ast.Flags) > 0 {
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msg += " " + strings.Join(ast.Flags, " ")
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}
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if cmd == "onbuild" {
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if ast.Next == nil {
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return fmt.Errorf("ONBUILD requires at least one argument")
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}
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ast = ast.Next.Children[0]
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strList = append(strList, ast.Value)
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msg += " " + ast.Value
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if len(ast.Flags) > 0 {
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msg += " " + strings.Join(ast.Flags, " ")
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}
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}
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// count the number of nodes that we are going to traverse first
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// so we can pre-create the argument and message array. This speeds up the
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// allocation of those list a lot when they have a lot of arguments
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cursor := ast
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var n int
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for cursor.Next != nil {
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cursor = cursor.Next
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n++
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}
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msgList := make([]string, n)
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var i int
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// Append the build-time args to config-environment.
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// This allows builder config to override the variables, making the behavior similar to
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// a shell script i.e. `ENV foo bar` overrides value of `foo` passed in build
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// context. But `ENV foo $foo` will use the value from build context if one
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// isn't already been defined by a previous ENV primitive.
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// Note, we get this behavior because we know that ProcessWord() will
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// stop on the first occurrence of a variable name and not notice
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// a subsequent one. So, putting the buildArgs list after the Config.Env
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// list, in 'envs', is safe.
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envs := b.runConfig.Env
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for key, val := range b.BuildArgs {
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if !b.isBuildArgAllowed(key) {
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// skip build-args that are not in allowed list, meaning they have
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// not been defined by an "ARG" Dockerfile command yet.
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// This is an error condition but only if there is no "ARG" in the entire
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// Dockerfile, so we'll generate any necessary errors after we parsed
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// the entire file (see 'leftoverArgs' processing in evaluator.go )
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continue
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}
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envs = append(envs, fmt.Sprintf("%s=%s", key, val))
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}
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for ast.Next != nil {
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ast = ast.Next
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var str string
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str = ast.Value
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if replaceEnvAllowed[cmd] {
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var err error
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var words []string
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if allowWordExpansion[cmd] {
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words, err = ProcessWords(str, envs)
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if err != nil {
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return err
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}
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strList = append(strList, words...)
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} else {
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str, err = ProcessWord(str, envs)
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if err != nil {
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return err
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}
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strList = append(strList, str)
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}
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} else {
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strList = append(strList, str)
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}
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msgList[i] = ast.Value
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i++
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}
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msg += " " + strings.Join(msgList, " ")
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fmt.Fprintln(b.Stdout, msg)
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// XXX yes, we skip any cmds that are not valid; the parser should have
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// picked these out already.
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if f, ok := evaluateTable[cmd]; ok {
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b.flags = NewBFlags()
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b.flags.Args = flags
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return f(b, strList, attrs, original)
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}
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return fmt.Errorf("Unknown instruction: %s", upperCasedCmd)
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}
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// platformSupports is a short-term function to give users a quality error
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// message if a Dockerfile uses a command not supported on the platform.
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func platformSupports(command string) error {
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if runtime.GOOS != "windows" {
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return nil
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}
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switch command {
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case "expose", "user", "stopsignal", "arg":
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return fmt.Errorf("The daemon on this platform does not support the command '%s'", command)
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}
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return nil
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}
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