Schema: implementation for Examples()

Author: joanlopez

schema.go

@@ -14,9 +14,10 @@ var (
 )
 
 var (
-	pathSchDef = cue.MakePath(cue.Hid("_#schema", "github.com/grafana/thema"))
-	pathSch    = cue.MakePath(cue.Str("schema"))
-	pathJoin   = cue.MakePath(cue.Hid("_join", "github.com/grafana/thema"))
+	pathSchDef   = cue.MakePath(cue.Hid("_#schema", "github.com/grafana/thema"))
+	pathExamples = cue.MakePath(cue.Str("examples"))
+	pathSch      = cue.MakePath(cue.Str("schema"))
+	pathJoin     = cue.MakePath(cue.Hid("_join", "github.com/grafana/thema"))
 )
 
 // schemaDef represents a single #SchemaDef, with a backlink to its containing
@@ -37,7 +38,23 @@ type schemaDef struct {
 // Examples returns the set of examples of this schema defined in the original
 // lineage. The string key is the name given to the example.
 func (sch *schemaDef) Examples() map[string]*Instance {
-	panic("TODO")
+	examplesNode := sch.Underlying().LookupPath(pathExamples)
+	it, err := examplesNode.Fields()
+	if err != nil {
+		panic(err)
+	}
+
+	examples := make(map[string]*Instance)
+	for it.Next() {
+		label := it.Label()
+		examples[label] = &Instance{
+			raw:  it.Value(),
+			name: label,
+			sch:  sch,
+		}
+	}
+
+	return examples
 }
 
 func (sch *schemaDef) rt() *Runtime {

schema_test.go

@@ -7,6 +7,9 @@ import (
 
 	"cuelang.org/go/cue/cuecontext"
 	"cuelang.org/go/cue/errors"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 var linstr = `name: "single"
@@ -17,6 +20,13 @@ schemas: [{
 		anint:   int64 | *42
 		abool:   bool
 	}
+	examples: {
+		simple: {
+			astring: "some string"
+			anint:  42
+			abool:  true
+		}
+	}
 }]
 `
 
@@ -76,6 +86,33 @@ func TestBindType(t *testing.T) {
 	}
 }
 
+func TestSchema_Examples(t *testing.T) {
+	lin := testLin()
+
+	sch := lin.First()
+	examples := sch.Examples()
+	require.NotNil(t, examples)
+
+	// There must be a "simple" example based on
+	// the definition above (beginning of file).
+	require.NotEmpty(t, examples)
+	require.NotNil(t, examples["simple"])
+
+	tt := &TestType{}
+	ts, err := BindType[*TestType](sch, tt)
+	require.NoError(t, err)
+
+	tinst, err := ts.ValidateTyped(examples["simple"].Underlying())
+	require.NoError(t, err)
+
+	val, err := tinst.Value()
+	require.NoError(t, err)
+
+	assert.Equal(t, "some string", *val.Astring)
+	assert.Equal(t, int64(42), val.Anint)
+	assert.Equal(t, true, val.Abool)
+}
+
 // scratch test, preserved only as a simpler sandbox for future playing with pointers, generics, reflect
 func testPointerNewVar(t *testing.T) {
 	type Foo struct {

surface.go

@@ -215,6 +215,10 @@ type Schema interface {
 	// Lineage returns the lineage that contains this schema.
 	Lineage() Lineage
 
+	// Examples returns the set of examples of this schema defined in the original
+	// lineage. The string key is the name given to the example.
+	Examples() map[string]*Instance
+
 	// Schema must be a private interface in order to ensure all instances fully
 	// conform to Thema invariants.
 	_schema()