[Compose] Cast values to expected type after interpolating values

cli/compose/interpolation/interpolation.go

@@ -1,75 +1,71 @@
 package interpolation
 
 import (
+	"os"
+	"strings"
+
 	"github.com/docker/cli/cli/compose/template"
 	"github.com/pkg/errors"
 )
 
-// Interpolate replaces variables in a string with the values from a mapping
-func Interpolate(config map[string]interface{}, section string, mapping template.Mapping) (map[string]interface{}, error) {
-	out := map[string]interface{}{}
+// Options supported by Interpolate
+type Options struct {
+	// LookupValue from a key
+	LookupValue LookupValue
+	// TypeCastMapping maps key paths to functions to cast to a type
+	TypeCastMapping map[Path]Cast
+}
 
-	for name, item := range config {
-		if item == nil {
-			out[name] = nil
-			continue
-		}
-		mapItem, ok := item.(map[string]interface{})
-		if !ok {
-			return nil, errors.Errorf("Invalid type for %s : %T instead of %T", name, item, out)
-		}
-		interpolatedItem, err := interpolateSectionItem(name, mapItem, section, mapping)
-		if err != nil {
-			return nil, err
-		}
-		out[name] = interpolatedItem
-	}
+// LookupValue is a function which maps from variable names to values.
+// Returns the value as a string and a bool indicating whether
+// the value is present, to distinguish between an empty string
+// and the absence of a value.
+type LookupValue func(key string) (string, bool)
 
-	return out, nil
-}
+// Cast a value to a new type, or return an error if the value can't be cast
+type Cast func(value string) (interface{}, error)
 
-func interpolateSectionItem(
-	name string,
-	item map[string]interface{},
-	section string,
-	mapping template.Mapping,
-) (map[string]interface{}, error) {
+// Interpolate replaces variables in a string with the values from a mapping
+func Interpolate(config map[string]interface{}, opts Options) (map[string]interface{}, error) {
+	if opts.LookupValue == nil {
+		opts.LookupValue = os.LookupEnv
+	}
+	if opts.TypeCastMapping == nil {
+		opts.TypeCastMapping = make(map[Path]Cast)
+	}
 
 	out := map[string]interface{}{}
 
-	for key, value := range item {
-		interpolatedValue, err := recursiveInterpolate(value, mapping)
-		switch err := err.(type) {
-		case nil:
-		case *template.InvalidTemplateError:
-			return nil, errors.Errorf(
-				"Invalid interpolation format for %#v option in %s %#v: %#v. You may need to escape any $ with another $.",
-				key, section, name, err.Template,
-			)
-		default:
-			return nil, errors.Wrapf(err, "error while interpolating %s in %s %s", key, section, name)
+	for key, value := range config {
+		interpolatedValue, err := recursiveInterpolate(value, NewPath(key), opts)
+		if err != nil {
+			return out, err
 		}
 		out[key] = interpolatedValue
 	}
 
 	return out, nil
-
 }
 
-func recursiveInterpolate(
-	value interface{},
-	mapping template.Mapping,
-) (interface{}, error) {
-
+func recursiveInterpolate(value interface{}, path Path, opts Options) (interface{}, error) {
 	switch value := value.(type) {
 
 	case string:
-		return template.Substitute(value, mapping)
+		newValue, err := template.Substitute(value, template.Mapping(opts.LookupValue))
+		if err != nil || newValue == value {
+			return value, newPathError(path, err)
+		}
+		caster, ok := opts.getCasterForPath(path)
+		if !ok {
+			return newValue, nil
+		}
+		casted, err := caster(newValue)
+		return casted, newPathError(path, errors.Wrap(err, "failed to cast to expected type"))
 
 	case map[string]interface{}:
 		out := map[string]interface{}{}
 		for key, elem := range value {
-			interpolatedElem, err := recursiveInterpolate(elem, mapping)
+			interpolatedElem, err := recursiveInterpolate(elem, path.Next(key), opts)
 			if err != nil {
 				return nil, err
 			}
@@ -80,7 +76,7 @@ func recursiveInterpolate(
 	case []interface{}:
 		out := make([]interface{}, len(value))
 		for i, elem := range value {
-			interpolatedElem, err := recursiveInterpolate(elem, mapping)
+			interpolatedElem, err := recursiveInterpolate(elem, path.Next(PathMatchList), opts)
 			if err != nil {
 				return nil, err
 			}
@@ -92,5 +88,71 @@ func recursiveInterpolate(
 		return value, nil
 
 	}
+}
+
+func newPathError(path Path, err error) error {
+	switch err := err.(type) {
+	case nil:
+		return nil
+	case *template.InvalidTemplateError:
+		return errors.Errorf(
+			"invalid interpolation format for %s: %#v. You may need to escape any $ with another $.",
+			path, err.Template)
+	default:
+		return errors.Wrapf(err, "error while interpolating %s", path)
+	}
+}
+
+const pathSeparator = "."
+
+// PathMatchAll is a token used as part of a Path to match any key at that level
+// in the nested structure
+const PathMatchAll = "*"
+
+// PathMatchList is a token used as part of a Path to match items in a list
+const PathMatchList = "[]"
+
+// Path is a dotted path of keys to a value in a nested mapping structure. A *
+// section in a path will match any key in the mapping structure.
+type Path string
+
+// NewPath returns a new Path
+func NewPath(items ...string) Path {
+	return Path(strings.Join(items, pathSeparator))
+}
+
+// Next returns a new path by append part to the current path
+func (p Path) Next(part string) Path {
+	return Path(string(p) + pathSeparator + part)
+}
+
+func (p Path) parts() []string {
+	return strings.Split(string(p), pathSeparator)
+}
+
+func (p Path) matches(pattern Path) bool {
+	patternParts := pattern.parts()
+	parts := p.parts()
+
+	if len(patternParts) != len(parts) {
+		return false
+	}
+	for index, part := range parts {
+		switch patternParts[index] {
+		case PathMatchAll, part:
+			continue
+		default:
+			return false
+		}
+	}
+	return true
+}
 
+func (o Options) getCasterForPath(path Path) (Cast, bool) {
+	for pattern, caster := range o.TypeCastMapping {
+		if path.matches(pattern) {
+			return caster, true
+		}
+	}
+	return nil, false
 }

cli/compose/interpolation/interpolation_test.go

@@ -3,12 +3,16 @@ package interpolation
 import (
 	"testing"
 
+	"strconv"
+
+	"github.com/gotestyourself/gotestyourself/env"
 	"github.com/stretchr/testify/assert"
 )
 
 var defaults = map[string]string{
-	"USER": "jenny",
-	"FOO":  "bar",
+	"USER":  "jenny",
+	"FOO":   "bar",
+	"count": "5",
 }
 
 func defaultMapping(name string) (string, bool) {
@@ -41,7 +45,7 @@ func TestInterpolate(t *testing.T) {
 			},
 		},
 	}
-	result, err := Interpolate(services, "service", defaultMapping)
+	result, err := Interpolate(services, Options{LookupValue: defaultMapping})
 	assert.NoError(t, err)
 	assert.Equal(t, expected, result)
 }
@@ -52,6 +56,91 @@ func TestInvalidInterpolation(t *testing.T) {
 			"image": "${",
 		},
 	}
-	_, err := Interpolate(services, "service", defaultMapping)
-	assert.EqualError(t, err, `Invalid interpolation format for "image" option in service "servicea": "${". You may need to escape any $ with another $.`)
+	_, err := Interpolate(services, Options{LookupValue: defaultMapping})
+	assert.EqualError(t, err, `invalid interpolation format for servicea.image: "${". You may need to escape any $ with another $.`)
+}
+
+func TestInterpolateWithDefaults(t *testing.T) {
+	defer env.Patch(t, "FOO", "BARZ")()
+
+	config := map[string]interface{}{
+		"networks": map[string]interface{}{
+			"foo": "thing_${FOO}",
+		},
+	}
+	expected := map[string]interface{}{
+		"networks": map[string]interface{}{
+			"foo": "thing_BARZ",
+		},
+	}
+	result, err := Interpolate(config, Options{})
+	assert.NoError(t, err)
+	assert.Equal(t, expected, result)
+}
+
+func TestInterpolateWithCast(t *testing.T) {
+	config := map[string]interface{}{
+		"foo": map[string]interface{}{
+			"replicas": "$count",
+		},
+	}
+	toInt := func(value string) (interface{}, error) {
+		return strconv.Atoi(value)
+	}
+	result, err := Interpolate(config, Options{
+		LookupValue:     defaultMapping,
+		TypeCastMapping: map[Path]Cast{NewPath(PathMatchAll, "replicas"): toInt},
+	})
+	assert.NoError(t, err)
+	expected := map[string]interface{}{
+		"foo": map[string]interface{}{
+			"replicas": 5,
+		},
+	}
+	assert.Equal(t, expected, result)
+}
+
+func TestPathMatches(t *testing.T) {
+	var testcases = []struct {
+		doc      string
+		path     Path
+		pattern  Path
+		expected bool
+	}{
+		{
+			doc:     "pattern too short",
+			path:    NewPath("one", "two", "three"),
+			pattern: NewPath("one", "two"),
+		},
+		{
+			doc:     "pattern too long",
+			path:    NewPath("one", "two"),
+			pattern: NewPath("one", "two", "three"),
+		},
+		{
+			doc:     "pattern mismatch",
+			path:    NewPath("one", "three", "two"),
+			pattern: NewPath("one", "two", "three"),
+		},
+		{
+			doc:     "pattern mismatch with match-all part",
+			path:    NewPath("one", "three", "two"),
+			pattern: NewPath(PathMatchAll, "two", "three"),
+		},
+		{
+			doc:      "pattern match with match-all part",
+			path:     NewPath("one", "two", "three"),
+			pattern:  NewPath("one", "*", "three"),
+			expected: true,
+		},
+		{
+			doc:      "pattern match",
+			path:     NewPath("one", "two", "three"),
+			pattern:  NewPath("one", "two", "three"),
+			expected: true,
+		},
+	}
+	for _, testcase := range testcases {
+		assert.Equal(t, testcase.expected, testcase.path.matches(testcase.pattern))
+	}
 }

cli/compose/loader/interpolate.go

@@ -0,0 +1,74 @@
+package loader
+
+import (
+	"strconv"
+	"strings"
+
+	interp "github.com/docker/cli/cli/compose/interpolation"
+	"github.com/pkg/errors"
+)
+
+var interpolateTypeCastMapping = map[interp.Path]interp.Cast{
+	servicePath("configs", interp.PathMatchList, "mode"):             toInt,
+	servicePath("secrets", interp.PathMatchList, "mode"):             toInt,
+	servicePath("healthcheck", "retries"):                            toInt,
+	servicePath("healthcheck", "disable"):                            toBoolean,
+	servicePath("deploy", "replicas"):                                toInt,
+	servicePath("deploy", "update_config", "parallelism"):            toInt,
+	servicePath("deploy", "update_config", "max_failure_ratio"):      toFloat,
+	servicePath("deploy", "restart_policy", "max_attempts"):          toInt,
+	servicePath("ports", interp.PathMatchList, "target"):             toInt,
+	servicePath("ports", interp.PathMatchList, "published"):          toInt,
+	servicePath("ulimits", interp.PathMatchAll):                      toInt,
+	servicePath("ulimits", interp.PathMatchAll, "hard"):              toInt,
+	servicePath("ulimits", interp.PathMatchAll, "soft"):              toInt,
+	servicePath("privileged"):                                        toBoolean,
+	servicePath("read_only"):                                         toBoolean,
+	servicePath("stdin_open"):                                        toBoolean,
+	servicePath("tty"):                                               toBoolean,
+	servicePath("volumes", interp.PathMatchList, "read_only"):        toBoolean,
+	servicePath("volumes", interp.PathMatchList, "volume", "nocopy"): toBoolean,
+	iPath("networks", interp.PathMatchAll, "external"):               toBoolean,
+	iPath("networks", interp.PathMatchAll, "internal"):               toBoolean,
+	iPath("networks", interp.PathMatchAll, "attachable"):             toBoolean,
+	iPath("volumes", interp.PathMatchAll, "external"):                toBoolean,
+	iPath("secrets", interp.PathMatchAll, "external"):                toBoolean,
+	iPath("configs", interp.PathMatchAll, "external"):                toBoolean,
+}
+
+func iPath(parts ...string) interp.Path {
+	return interp.NewPath(parts...)
+}
+
+func servicePath(parts ...string) interp.Path {
+	return iPath(append([]string{"services", interp.PathMatchAll}, parts...)...)
+}
+
+func toInt(value string) (interface{}, error) {
+	return strconv.Atoi(value)
+}
+
+func toFloat(value string) (interface{}, error) {
+	return strconv.ParseFloat(value, 64)
+}
+
+// should match http://yaml.org/type/bool.html
+func toBoolean(value string) (interface{}, error) {
+	switch strings.ToLower(value) {
+	case "y", "yes", "true", "on":
+		return true, nil
+	case "n", "no", "false", "off":
+		return false, nil
+	default:
+		return nil, errors.Errorf("invalid boolean: %s", value)
+	}
+}
+
+func interpolateConfig(configDict map[string]interface{}, lookupEnv interp.LookupValue) (map[string]interface{}, error) {
+	return interp.Interpolate(
+		configDict,
+		interp.Options{
+			LookupValue:     lookupEnv,
+			TypeCastMapping: interpolateTypeCastMapping,
+		})
+}