[confmap] Validate providers scheme when building a Resolver

.chloggen/mx-psi_restrict-providers-scheme.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: confmap
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Check that providers have a correct scheme when building a confmap.Resolver.
+
+# One or more tracking issues or pull requests related to the change
+issues: []
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

confmap/resolver.go

@@ -96,7 +96,17 @@ func NewResolver(set ResolverSettings) (*Resolver, error) {
 	providers := make(map[string]Provider, len(set.ProviderFactories))
 	for _, factory := range set.ProviderFactories {
 		provider := factory.Create(set.ProviderSettings)
-		providers[provider.Scheme()] = provider
+		scheme := provider.Scheme()
+		// Check that the scheme follows the pattern.
+		if !regexp.MustCompile(schemePattern).MatchString(scheme) {
+			return nil, fmt.Errorf("invalid 'confmap.Provider' scheme %q", scheme)
+		}
+		// Check that the scheme is unique.
+		if _, ok := providers[scheme]; ok {
+			return nil, fmt.Errorf("duplicate 'confmap.Provider' scheme %q", scheme)
+		}
+
+		providers[scheme] = provider
 	}
 
 	if set.DefaultScheme != "" {