[confmap] Fix double-expansion of escaped environment variables

This change fixes the issue where environment variables escaped with $$ were double-expanded. The collector now converts `$${ENV_VAR}` to `${ENV_VAR}` and `$$ENV_VAR` to `$ENV_VAR` without further expansion.

Author: dmitryax

.chloggen/fix-env-var-double-escaping.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# 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: Fix double-expansion of environment variables escaped with `$$`, e.g. `$${ENV_VAR}` and `$$ENV_VAR`.
+
+# One or more tracking issues or pull requests related to the change
+issues: [10713]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+  This change fixes the issue where environment variables escaped with $$ were double-expanded. 
+  The collector now converts `$${ENV_VAR}` to `${ENV_VAR}` and `$$ENV_VAR` to `$ENV_VAR` without further expansion.
+
+# 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/converter/expandconverter/expand.go

@@ -85,6 +85,7 @@ func (c converter) expandEnv(s string) (string, error) {
 		// - $FOO will be substituted with env var FOO
 		// - $$FOO will be replaced with $FOO
 		// - $$$FOO will be replaced with $ + substituted env var FOO
+		// TODO: Move the escaping of $$ out from the expand converter to the resolver.
 		if str == "$" {
 			return "$"
 		}

confmap/expand_test.go

@@ -583,21 +583,21 @@ func Test_EscapedEnvVars(t *testing.T) {
 
 	expectedMap := map[string]any{
 		"test_map": map[string]any{
-			"recv.1":  "$MAP_VALUE_1",
-			"recv.2":  "$$MAP_VALUE_2",
-			"recv.3":  "$$MAP_VALUE_3",
-			"recv.4":  "$" + mapValue2,
-			"recv.5":  "some${MAP_VALUE_4}text",
-			"recv.6":  "${ONE}${TWO}",
-			"recv.7":  "text$",
-			"recv.8":  "$",
-			"recv.9":  "${1}${env:2}",
-			"recv.10": "some${env:MAP_VALUE_4}text",
-			"recv.11": "${env:" + mapValue2 + "}",
-			"recv.12": "${env:${MAP_VALUE_2}}",
-			"recv.13": "env:MAP_VALUE_2}${MAP_VALUE_2}{",
-			"recv.14": "${env:MAP_VALUE_2${MAP_VALUE_2}",
-			"recv.15": "$" + mapValue2,
+			"recv.1":  "$$MAP_VALUE_1",
+			"recv.2":  "$$$MAP_VALUE_2",
+			"recv.3":  "$$$$MAP_VALUE_3",
+			"recv.4":  "$$" + mapValue2,
+			"recv.5":  "some$${MAP_VALUE_4}text",
+			"recv.6":  "$${ONE}$${TWO}",
+			"recv.7":  "text$$",
+			"recv.8":  "$$",
+			"recv.9":  "$${1}$${env:2}",
+			"recv.10": "some$${env:MAP_VALUE_4}text",
+			"recv.11": "$${env:" + mapValue2 + "}",
+			"recv.12": "$${env:$${MAP_VALUE_2}}",
+			"recv.13": "env:MAP_VALUE_2}$${MAP_VALUE_2}{",
+			"recv.14": "${env:MAP_VALUE_2$${MAP_VALUE_2}",
+			"recv.15": "$$" + mapValue2,
 		}}
 
 	fileProvider := newFakeProvider("file", func(_ context.Context, uri string, _ WatcherFunc) (*Retrieved, error) {

confmap/resolver.go

@@ -12,8 +12,6 @@ import (
 
 	"go.uber.org/multierr"
 	"go.uber.org/zap"
-
-	"go.opentelemetry.io/collector/internal/globalgates"
 )
 
 // follows drive-letter specification:
@@ -173,13 +171,7 @@ func (mr *Resolver) Resolve(ctx context.Context) (*Conf, error) {
 		if err != nil {
 			return nil, err
 		}
-
-		if v, ok := val.(string); ok && globalgates.UseUnifiedEnvVarExpansionRules.IsEnabled() {
-			cfgMap[k] = strings.ReplaceAll(v, "$$", "$")
-		} else {
-			cfgMap[k] = val
-		}
-
+		cfgMap[k] = val
 	}
 	retMap = NewFromStringMap(cfgMap)