Add support for no-arg commands in Dockerfile

We're hoping to add some new commands that don't have any args so this
PR will enable that by removing all of the hard-coded checks that require
commands to have at least one arg.  It also adds some checks to each
command so we're consistent in the error message we get.  Added a test
for this too.

We actually had this check in at least 3 different places (twice in the
parser and once in most cmds), this removes 2 of them (the parser ones).

Had to remove/modify some testcases because its now legal to have certain
commands w/o args - e.g. RUN. This was actually inconsistent because
we used to allow "RUN []" but not "RUN" even though they would generate
(almost) the same net result.  Now we're consistent.

Signed-off-by: Doug Davis <dug@us.ibm.com>

builder/dispatchers.go

@@ -39,7 +39,7 @@ func nullDispatch(b *Builder, args []string, attributes map[string]bool, origina
 //
 func env(b *Builder, args []string, attributes map[string]bool, original string) error {
 	if len(args) == 0 {
-		return fmt.Errorf("ENV is missing arguments")
+		return fmt.Errorf("ENV requires at least one argument")
 	}
 
 	if len(args)%2 != 0 {
@@ -78,7 +78,7 @@ func env(b *Builder, args []string, attributes map[string]bool, original string)
 // Sets the maintainer metadata.
 func maintainer(b *Builder, args []string, attributes map[string]bool, original string) error {
 	if len(args) != 1 {
-		return fmt.Errorf("MAINTAINER requires only one argument")
+		return fmt.Errorf("MAINTAINER requires exactly one argument")
 	}
 
 	b.maintainer = args[0]
@@ -159,6 +159,10 @@ func from(b *Builder, args []string, attributes map[string]bool, original string
 // cases.
 //
 func onbuild(b *Builder, args []string, attributes map[string]bool, original string) error {
+	if len(args) == 0 {
+		return fmt.Errorf("ONBUILD requires at least one argument")
+	}
+
 	triggerInstruction := strings.ToUpper(strings.TrimSpace(args[0]))
 	switch triggerInstruction {
 	case "ONBUILD":
@@ -327,6 +331,10 @@ func entrypoint(b *Builder, args []string, attributes map[string]bool, original
 func expose(b *Builder, args []string, attributes map[string]bool, original string) error {
 	portsTab := args
 
+	if len(args) == 0 {
+		return fmt.Errorf("EXPOSE requires at least one argument")
+	}
+
 	if b.Config.ExposedPorts == nil {
 		b.Config.ExposedPorts = make(nat.PortSet)
 	}
@@ -373,7 +381,7 @@ func user(b *Builder, args []string, attributes map[string]bool, original string
 //
 func volume(b *Builder, args []string, attributes map[string]bool, original string) error {
 	if len(args) == 0 {
-		return fmt.Errorf("Volume cannot be empty")
+		return fmt.Errorf("VOLUME requires at least one argument")
 	}
 
 	if b.Config.Volumes == nil {

builder/evaluator.go

@@ -240,6 +240,9 @@ func (b *Builder) dispatch(stepN int, ast *parser.Node) error {
 	msg := fmt.Sprintf("Step %d : %s", stepN, strings.ToUpper(cmd))
 
 	if cmd == "onbuild" {
+		if ast.Next == nil {
+			return fmt.Errorf("ONBUILD requires at least one argument")
+		}
 		ast = ast.Next.Children[0]
 		strs = append(strs, ast.Value)
 		msg += " " + ast.Value

builder/parser/line_parsers.go

@@ -30,6 +30,10 @@ func parseIgnore(rest string) (*Node, map[string]bool, error) {
 // ONBUILD RUN foo bar -> (onbuild (run foo bar))
 //
 func parseSubCommand(rest string) (*Node, map[string]bool, error) {
+	if rest == "" {
+		return nil, nil, nil
+	}
+
 	_, child, err := parseLine(rest)
 	if err != nil {
 		return nil, nil, err
@@ -133,7 +137,7 @@ func parseEnv(rest string) (*Node, map[string]bool, error) {
 	}
 
 	if len(words) == 0 {
-		return nil, nil, fmt.Errorf("ENV must have some arguments")
+		return nil, nil, fmt.Errorf("ENV requires at least one argument")
 	}
 
 	// Old format (ENV name value)
@@ -181,6 +185,10 @@ func parseEnv(rest string) (*Node, map[string]bool, error) {
 // parses a whitespace-delimited set of arguments. The result is effectively a
 // linked list of string arguments.
 func parseStringsWhitespaceDelimited(rest string) (*Node, map[string]bool, error) {
+	if rest == "" {
+		return nil, nil, nil
+	}
+
 	node := &Node{}
 	rootnode := node
 	prevnode := node
@@ -201,6 +209,9 @@ func parseStringsWhitespaceDelimited(rest string) (*Node, map[string]bool, error
 
 // parsestring just wraps the string in quotes and returns a working node.
 func parseString(rest string) (*Node, map[string]bool, error) {
+	if rest == "" {
+		return nil, nil, nil
+	}
 	n := &Node{}
 	n.Value = rest
 	return n, nil, nil
@@ -235,7 +246,9 @@ func parseJSON(rest string) (*Node, map[string]bool, error) {
 // so, passes to parseJSON; if not, quotes the result and returns a single
 // node.
 func parseMaybeJSON(rest string) (*Node, map[string]bool, error) {
-	rest = strings.TrimSpace(rest)
+	if rest == "" {
+		return nil, nil, nil
+	}
 
 	node, attrs, err := parseJSON(rest)
 
@@ -255,8 +268,6 @@ func parseMaybeJSON(rest string) (*Node, map[string]bool, error) {
 // so, passes to parseJSON; if not, attmpts to parse it as a whitespace
 // delimited string.
 func parseMaybeJSONToList(rest string) (*Node, map[string]bool, error) {
-	rest = strings.TrimSpace(rest)
-
 	node, attrs, err := parseJSON(rest)
 
 	if err == nil {

builder/parser/parser.go

@@ -3,7 +3,6 @@ package parser
 
 import (
 	"bufio"
-	"fmt"
 	"io"
 	"regexp"
 	"strings"
@@ -78,10 +77,6 @@ func parseLine(line string) (string, *Node, error) {
 		return "", nil, err
 	}
 
-	if len(args) == 0 {
-		return "", nil, fmt.Errorf("Instruction %q is empty; cannot continue", cmd)
-	}
-
 	node := &Node{}
 	node.Value = cmd
 

builder/parser/testfiles-negative/empty-instruction/Dockerfile

@@ -1,8 +0,0 @@
-FROM dockerfile/rabbitmq
-
-RUN
-  rabbitmq-plugins enable \
-   rabbitmq_shovel \
-   rabbitmq_shovel_management \
-   rabbitmq_federation \
-   rabbitmq_federation_management

builder/parser/testfiles-negative/html-page-yes-really-thanks-lk4d4/Dockerfile

@@ -1,2 +0,0 @@
-<html>
-</html>

builder/parser/utils.go

@@ -1,7 +1,6 @@
 package parser
 
 import (
-	"fmt"
 	"strconv"
 	"strings"
 )
@@ -50,17 +49,19 @@ func fullDispatch(cmd, args string) (*Node, map[string]bool, error) {
 // splitCommand takes a single line of text and parses out the cmd and args,
 // which are used for dispatching to more exact parsing functions.
 func splitCommand(line string) (string, string, error) {
+	var args string
+
 	// Make sure we get the same results irrespective of leading/trailing spaces
 	cmdline := TOKEN_WHITESPACE.Split(strings.TrimSpace(line), 2)
+	cmd := strings.ToLower(cmdline[0])
 
-	if len(cmdline) != 2 {
+	if len(cmdline) == 2 {
-		return "", "", fmt.Errorf("We do not understand this file. Please ensure it is a valid Dockerfile. Parser error at %q", line)
+		args = strings.TrimSpace(cmdline[1])
 	}
 
-	cmd := strings.ToLower(cmdline[0])
 	// the cmd should never have whitespace, but it's possible for the args to
 	// have trailing whitespace.
-	return cmd, strings.TrimSpace(cmdline[1]), nil
+	return cmd, args, nil
 }
 
 // covers comments and empty lines. Lines should be trimmed before passing to

integration-cli/docker_cli_build_test.go

@@ -49,14 +49,14 @@ func TestBuildEmptyWhitespace(t *testing.T) {
 		name,
 		`
     FROM busybox
-    RUN 
+    COPY
       quux \
       bar
     `,
 		true)
 
 	if err == nil {
-		t.Fatal("no error when dealing with a RUN statement with no content on the same line")
+		t.Fatal("no error when dealing with a COPY statement with no content on the same line")
 	}
 
 	logDone("build - statements with whitespace and no content should generate a parse error")
@@ -4822,3 +4822,51 @@ func TestBuildVolumeFileExistsinContainer(t *testing.T) {
 
 	logDone("build - errors when volume is specified where a file exists")
 }
+
+func TestBuildMissingArgs(t *testing.T) {
+	// test to make sure these cmds w/o any args will generate an error
+	// Notice some commands are missing because its ok for them to
+	// not have any args - like: CMD, RUN, ENTRYPOINT
+	cmds := []string{
+		"ADD",
+		"COPY",
+		"ENV",
+		"EXPOSE",
+		"FROM",
+		"MAINTAINER",
+		"ONBUILD",
+		"USER",
+		"VOLUME",
+		"WORKDIR",
+	}
+
+	defer deleteAllContainers()
+
+	for _, cmd := range cmds {
+		var dockerfile string
+
+		if cmd == "FROM" {
+			dockerfile = cmd
+		} else {
+			// Add FROM to make sure we don't complain about it missing
+			dockerfile = "FROM busybox\n" + cmd
+		}
+
+		ctx, err := fakeContext(dockerfile, map[string]string{})
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer ctx.Close()
+		var out string
+		if out, err = buildImageFromContext("args", ctx, true); err == nil {
+			t.Fatalf("%s was supposed to fail:%s", cmd, out)
+		}
+		if !strings.Contains(err.Error(), cmd+" requires") {
+			t.Fatalf("%s returned the wrong type of error:%s", cmd, err)
+		}
+
+		ctx.Close()
+	}
+
+	logDone("build - verify missing args")
+}