cache fix: stable ordering of maps (Env, Mount, ...)

Maps were causing the same Pipeline to randomly produce slightly different LLB
on each run (because they are represented as an array in LLB, wheras
they're a map in CueLLB).

This forces every Cue field iteration (env, mount, etc) to be
predictable by using stable sorting.

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

dagger/compiler/value.go

@@ -1,6 +1,8 @@
 package compiler
 
 import (
+	"sort"
+
 	"cuelang.org/go/cue"
 	cueformat "cuelang.org/go/cue/format"
 )
@@ -72,9 +74,33 @@ func (v *Value) Kind() cue.Kind {
 	return v.val.Kind()
 }
 
+// Field represents a struct field
+type Field struct {
+	Label string
+	Value *Value
+}
+
 // Proxy function to the underlying cue.Value
-func (v *Value) Fields() (*cue.Iterator, error) {
-	return v.val.Fields()
+// Field ordering is guaranteed to be stable.
+func (v *Value) Fields() ([]Field, error) {
+	it, err := v.val.Fields()
+	if err != nil {
+		return nil, err
+	}
+
+	fields := []Field{}
+	for it.Next() {
+		fields = append(fields, Field{
+			Label: it.Label(),
+			Value: v.Wrap(it.Value()),
+		})
+	}
+
+	sort.SliceStable(fields, func(i, j int) bool {
+		return fields[i].Label < fields[j].Label
+	})
+
+	return fields, nil
 }
 
 // Proxy function to the underlying cue.Value
@@ -121,38 +147,10 @@ func (v *Value) List() ([]*Value, error) {
 	for it.Next() {
 		l = append(l, v.Wrap(it.Value()))
 	}
+
 	return l, nil
 }
 
-// FIXME: deprecate to simplify
-func (v *Value) RangeList(fn func(int, *Value) error) error {
-	it, err := v.val.List()
-	if err != nil {
-		return err
-	}
-	i := 0
-	for it.Next() {
-		if err := fn(i, v.Wrap(it.Value())); err != nil {
-			return err
-		}
-		i++
-	}
-	return nil
-}
-
-func (v *Value) RangeStruct(fn func(string, *Value) error) error {
-	it, err := v.Fields()
-	if err != nil {
-		return err
-	}
-	for it.Next() {
-		if err := fn(it.Label(), v.Wrap(it.Value())); err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
 // FIXME: receive string path?
 func (v *Value) Merge(x interface{}, path ...string) (*Value, error) {
 	if xval, ok := x.(*Value); ok {

dagger/pipeline.go

@@ -112,12 +112,15 @@ func analyzeOp(fn func(*compiler.Value) error, op *compiler.Value) error {
 	case "load", "copy":
 		return Analyze(fn, op.Get("from"))
 	case "exec":
-		return op.Get("mount").RangeStruct(func(dest string, mnt *compiler.Value) error {
-			if from := mnt.Get("from"); from.Exists() {
+		fields, err := op.Get("mount").Fields()
+		if err != nil {
+			return err
+		}
+		for _, mnt := range fields {
+			if from := mnt.Value.Get("from"); from.Exists() {
 				return Analyze(fn, from)
 			}
-			return nil
-		})
+		}
 	}
 	return nil
 }
@@ -337,7 +340,6 @@ func (p *Pipeline) Exec(ctx context.Context, op *compiler.Value, st llb.State) (
 	opts := []llb.RunOption{}
 	var cmd struct {
 		Args   []string
-		Env    map[string]string
 		Dir    string
 		Always bool
 	}
@@ -349,10 +351,22 @@ func (p *Pipeline) Exec(ctx context.Context, op *compiler.Value, st llb.State) (
 	opts = append(opts, llb.Args(cmd.Args))
 	// dir
 	opts = append(opts, llb.Dir(cmd.Dir))
+
 	// env
-	for k, v := range cmd.Env {
-		opts = append(opts, llb.AddEnv(k, v))
+	if env := op.Get("env"); env.Exists() {
+		envs, err := op.Get("env").Fields()
+		if err != nil {
+			return st, err
+		}
+		for _, env := range envs {
+			v, err := env.Value.String()
+			if err != nil {
+				return st, err
+			}
+			opts = append(opts, llb.AddEnv(env.Label, v))
+		}
 	}
+
 	// always?
 	// FIXME: initialize once for an entire compute job, to avoid cache misses
 	if cmd.Always {
@@ -385,14 +399,17 @@ func (p *Pipeline) Exec(ctx context.Context, op *compiler.Value, st llb.State) (
 
 func (p *Pipeline) mountAll(ctx context.Context, mounts *compiler.Value) ([]llb.RunOption, error) {
 	opts := []llb.RunOption{}
-	err := mounts.RangeStruct(func(dest string, mnt *compiler.Value) error {
-		o, err := p.mount(ctx, dest, mnt)
+	fields, err := mounts.Fields()
+	if err != nil {
+		return nil, err
+	}
+	for _, mnt := range fields {
+		o, err := p.mount(ctx, mnt.Label, mnt.Value)
 		if err != nil {
-			return err
+			return nil, err
 		}
 		opts = append(opts, o)
-		return nil
-	})
+	}
 	return opts, err
 }
 
@@ -709,31 +726,31 @@ func (p *Pipeline) DockerBuild(ctx context.Context, op *compiler.Value, st llb.S
 	}
 
 	if buildArgs := op.Lookup("buildArg"); buildArgs.Exists() {
-		err := buildArgs.RangeStruct(func(key string, value *compiler.Value) error {
-			v, err := value.String()
-			if err != nil {
-				return err
-			}
-			req.FrontendOpt["build-arg:"+key] = v
-			return nil
-		})
+		fields, err := buildArgs.Fields()
 		if err != nil {
 			return st, err
 		}
+		for _, buildArg := range fields {
+			v, err := buildArg.Value.String()
+			if err != nil {
+				return st, err
+			}
+			req.FrontendOpt["build-arg:"+buildArg.Label] = v
+		}
 	}
 
 	if labels := op.Lookup("label"); labels.Exists() {
-		err := labels.RangeStruct(func(key string, value *compiler.Value) error {
-			s, err := value.String()
-			if err != nil {
-				return err
-			}
-			req.FrontendOpt["label:"+key] = s
-			return nil
-		})
+		fields, err := labels.Fields()
 		if err != nil {
 			return st, err
 		}
+		for _, label := range fields {
+			s, err := label.Value.String()
+			if err != nil {
+				return st, err
+			}
+			req.FrontendOpt["label:"+label.Label] = s
+		}
 	}
 
 	if platforms := op.Lookup("platforms"); platforms.Exists() {