Do no silently drop unknown schema data (#3743)

* Do no silently drop unknown schema data

* Add entry to changelog

* Add PR number to changelog

---------

Co-authored-by: Chester Cheung <cheung.zhy.csu@gmail.com>
Co-authored-by: Aaron Clawson <3766680+MadVikingGod@users.noreply.github.com>

schema/v1.1/parser.go

@@ -43,6 +43,7 @@ func ParseFile(schemaFilePath string) (*ast.Schema, error) {
 func Parse(schemaFileContent io.Reader) (*ast.Schema, error) {
 	var ts ast.Schema
 	d := yaml.NewDecoder(schemaFileContent)
+	d.SetStrict(true) // Do not silently drop unknown fields.
 	err := d.Decode(&ts)
 	if err != nil {
 		return nil, err

schema/v1.1/parser_test.go

@@ -167,8 +167,14 @@ func TestParseSchemaFile(t *testing.T) {
 	)
 }
 
-func TestFailParseSchemaFile(t *testing.T) {
+func TestFailParseFileUnsupportedFileFormat(t *testing.T) {
 	ts, err := ParseFile("testdata/unsupported-file-format.yaml")
-	assert.Error(t, err)
+	assert.ErrorContains(t, err, "unsupported schema file format minor version number")
+	assert.Nil(t, ts)
+}
+
+func TestFailParseFileUnknownField(t *testing.T) {
+	ts, err := ParseFile("testdata/unknown-field.yaml")
+	assert.ErrorContains(t, err, "field Resources not found in type ast.VersionDef")
 	assert.Nil(t, ts)
 }

schema/v1.1/testdata/unknown-field.yaml

@@ -0,0 +1,15 @@
+file_format: 1.1.0
+schema_url: https://opentelemetry.io/schemas/1.1.0
+
+versions:
+  1.1.0:
+    all: # Valid entry.
+      changes:
+        - rename_attributes:
+            k8s.cluster.name: kubernetes.cluster.name
+    Resources: # Invalid uppercase.
+      changes:
+        - rename_attributes:
+          attribute_map:
+            browser.user_agent: user_agent.original
+  1.0.0: