mcmp: make thread-safe, add InheritedValue, refactor Context/Annotation related methods

mcfg/cli.go

@@ -257,7 +257,7 @@ func (cli *SourceCLI) parse(
 		pvStrValOk = false
 	}
 	if pOk && !pvStrValOk {
-		ctx := mctx.Annotate(p.Component.Annotated(), "param", key)
+		ctx := mctx.Annotate(p.Component.Context(), "param", key)
 		return nil, merr.New("param expected a value", ctx)
 	}
 

mcfg/mcfg.go

@@ -131,7 +131,7 @@ func Populate(cmp *mcmp.Component, src Source) error {
 		if !p.Required {
 			continue
 		} else if _, ok := pvM[hash]; !ok {
-			ctx := mctx.Annotate(p.Component.Annotated(),
+			ctx := mctx.Annotate(p.Component.Context(),
 				"param", paramFullName(p.Component.Path(), p.Name))
 			return merr.New("required parameter is not set", ctx)
 		}

mcmp/component.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"strings"
+	"sync"
 
 	"github.com/mediocregopher/mediocre-go-lib/mctx"
 )
@@ -28,37 +29,76 @@ type child struct {
 // A new Component, i.e. the root Component in the hierarchy, can be initialized
 // by doing:
 //	new(Component).
+//
+// Method's on Component are thread-safe.
 type Component struct {
+	l sync.RWMutex
+
 	path     []string
 	parent   *Component
 	children []child
 
 	kv  map[interface{}]interface{}
+	ctx context.Context
 }
 
 // SetValue sets the given key to the given value on the Component, overwriting
 // any previous value for that key.
 func (c *Component) SetValue(key, value interface{}) {
+	c.l.Lock()
+	defer c.l.Unlock()
 	if c.kv == nil {
 		c.kv = make(map[interface{}]interface{}, 1)
 	}
 	c.kv[key] = value
 }
 
-// Value returns the value which has been set for the given key.
+func (c *Component) value(key interface{}) (interface{}, bool) {
-func (c *Component) Value(key interface{}) interface{} {
+	c.l.RLock()
-	return c.kv[key]
+	defer c.l.RUnlock()
+	if c.kv == nil {
+		return nil, false
+	}
+	value, ok := c.kv[key]
+	return value, ok
 }
 
-// Values returns all key/value pairs which have been set via SetValue. The
+// Value returns the value which has been set for the given key.
-// returned map should _not_ be modified.
+func (c *Component) Value(key interface{}) interface{} {
+	value, _ := c.value(key)
+	return value
+}
+
+// InheritedValue returns the value which has been set for the given key. It first
+// looks for the key on the receiver Component. If not found, it will look on
+// its parent Component, and so on, until the key is found. If the key is not
+// found on the root Component then false is returned.
+func (c *Component) InheritedValue(key interface{}) (interface{}, bool) {
+	value, ok := c.value(key)
+	if ok {
+		return value, ok
+	} else if c.parent == nil {
+		return nil, false
+	}
+	return c.parent.InheritedValue(key)
+}
+
+// Values returns all key/value pairs which have been set via SetValue.
 func (c *Component) Values() map[interface{}]interface{} {
-	return c.kv
+	c.l.RLock()
+	defer c.l.RUnlock()
+	out := make(map[interface{}]interface{}, len(c.kv))
+	for k, v := range c.kv {
+		out[k] = v
+	}
+	return out
 }
 
 // HasValue returns true if the given key has had a value set on it with
 // SetValue.
 func (c *Component) HasValue(key interface{}) bool {
+	c.l.RLock()
+	defer c.l.RUnlock()
 	_, ok := c.kv[key]
 	return ok
 }
@@ -69,6 +109,8 @@ func (c *Component) HasValue(key interface{}) bool {
 //
 // If a child of the given name has already been created this method will panic.
 func (c *Component) Child(name string) *Component {
+	c.l.Lock()
+	defer c.l.Unlock()
 	for _, child := range c.children {
 		if child.name == name {
 			panic(fmt.Sprintf("child with name %q already exists", name))
@@ -86,6 +128,8 @@ func (c *Component) Child(name string) *Component {
 // Children returns all Components created via the Child method on this
 // Component, in the order they were created.
 func (c *Component) Children() []*Component {
+	c.l.RLock()
+	defer c.l.RUnlock()
 	children := make([]*Component, len(c.children))
 	for i := range c.children {
 		children[i] = c.children[i].Component
@@ -97,6 +141,8 @@ func (c *Component) Children() []*Component {
 // or false if this Component was not created via Child (and is therefore the
 // root Component).
 func (c *Component) Name() (string, bool) {
+	c.l.RLock()
+	defer c.l.RUnlock()
 	if len(c.path) == 0 {
 		return "", false
 	}
@@ -115,11 +161,14 @@ func (c *Component) Name() (string, bool) {
 //	fmt.Printf("%#v\n", grandChild.Path())  // []string{"child", "grandchild"}
 //
 func (c *Component) Path() []string {
+	c.l.RLock()
+	defer c.l.RUnlock()
 	return c.path
 }
 
 func (c *Component) pathStr() string {
-	path := c.Path()
+	path := make([]string, len(c.path))
+	copy(path, c.path)
 	for i := range path {
 		path[i] = strings.ReplaceAll(path[i], "/", `\/`)
 	}
@@ -128,14 +177,28 @@ func (c *Component) pathStr() string {
 
 type annotateKey string
 
-// Annotate annotates the given Context with information about the Component.
+func (c *Component) getCtx() context.Context {
-func (c *Component) Annotate(ctx context.Context) context.Context {
+	if c.ctx == nil {
-	return mctx.Annotate(ctx, annotateKey("componentPath"), c.pathStr())
+		c.ctx = mctx.Annotated(annotateKey("componentPath"), c.pathStr())
+	}
+	return c.ctx
 }
 
-// Annotated is a shortcut for `c.Annotate(context.Background())`.
+// Annotate annotates the Component's internal Context in-place, such that they
-func (c *Component) Annotated() context.Context {
+// will be included in any future calls to the Context method.
-	return c.Annotate(context.Background())
+func (c *Component) Annotate(kv ...interface{}) {
+	c.l.Lock()
+	defer c.l.Unlock()
+	c.ctx = mctx.Annotate(c.getCtx(), kv...)
+}
+
+// Context returns a Context which has been annotated with any annotations from
+// Annotate calls to this Component, as well as some default annotations which
+// are always included.
+func (c *Component) Context() context.Context {
+	c.l.Lock()
+	defer c.l.Unlock()
+	return c.getCtx()
 }
 
 // BreadthFirstVisit visits this Component and all of its children, and their

mcmp/component_test.go

@@ -52,6 +52,24 @@ func TestComponent(t *T) {
 		assertValue(c, "bar", nil),
 		assertValue(child, "bar", 2),
 	)
+
+	assertInheritedValue := func(c *Component, key, expectedValue interface{}) massert.Assertion {
+		val, ok := c.InheritedValue(key)
+		return massert.All(
+			massert.Equal(expectedValue, val),
+			massert.Equal(expectedValue != nil, ok),
+		)
+	}
+
+	// test that InheritedValue does what it's supposed to
+	massert.Require(t,
+		assertInheritedValue(c, "foo", 1),
+		assertInheritedValue(child, "foo", 1),
+		assertInheritedValue(c, "bar", nil),
+		assertInheritedValue(child, "bar", 2),
+		assertInheritedValue(c, "xxx", nil),
+		assertInheritedValue(child, "xxx", nil),
+	)
 }
 func TestBreadFirstVisit(t *T) {
 	cmp := new(Component)