Check connection string env var before loading from a file (#3794)

agent/agent-tooling/src/main/java/com/microsoft/applicationinsights/agent/internal/configuration/ConfigurationBuilder.java

@@ -713,21 +713,12 @@ static void overlayFromEnv(
     StringLookup stringLookup =
         StringLookupFactory.INSTANCE.interpolatorStringLookup(stringLookupMap, null, false);
     StringSubstitutor stringSubstitutor = new StringSubstitutor(stringLookup);
-    String replacedConnectionString = stringSubstitutor.replace(config.connectionString);
-    if (replacedConnectionString != null
-        && !replacedConnectionString.startsWith("InstrumentationKey=")
-        && config.connectionString.equals(replacedConnectionString)) {
-      throw new FriendlyException(
-          "Your connection string seems to have a wrong format: \""
-              + config.connectionString
-              + "\").\n"
-              + "If you want to load the connection string from a file, please use this format:"
-              + "\n{ \"connectionString\": \"${file:connection-string-file.txt}\" }\n",
-          "Learn more about configuration options here: " + CONFIGURATION_OPTIONS_LINK);
-    }
     config.connectionString =
         overlayConnectionStringFromEnv(
-            replacedConnectionString, envVarsFunction, systemPropertiesFunction);
+            stringSubstitutor.replace(config.connectionString),
+            envVarsFunction,
+            systemPropertiesFunction);
+
     if (isTrimEmpty(config.role.name)) {
       // only use WEBSITE_SITE_NAME as a fallback
       config.role.name = getWebsiteSiteNameEnvVar(envVarsFunction);

agent/agent-tooling/src/test/java/com/microsoft/applicationinsights/agent/internal/configuration/ConfigurationBuilderTest.java

@@ -172,43 +172,9 @@ void testOverlayWithEnvVarWithGoodFileStringLookupFormat() throws Exception {
     assertThat(configuration.connectionString).isEqualTo(CONNECTION_STRING);
   }
 
-  @Test
-  void testOverlayWithEnvVarWithBadFileStringLookupFormat() throws Exception {
-    Configuration configuration = new Configuration();
-    String filename = "${file:" + connectionStringFile.getAbsolutePath();
-    configuration.connectionString = filename;
-    assertFriendlyExceptionThrown(configuration, filename);
-
-    filename = "${xyz:" + connectionStringFile.getAbsolutePath() + "}";
-    configuration.connectionString = filename;
-    assertFriendlyExceptionThrown(configuration, filename);
-
-    filename = "file:" + connectionStringFile.getAbsolutePath() + "}";
-    configuration.connectionString = filename;
-    assertFriendlyExceptionThrown(configuration, filename);
-
-    filename = "file:" + connectionStringFile.getAbsolutePath();
-    configuration.connectionString = filename;
-    assertFriendlyExceptionThrown(configuration, filename);
-
-    configuration.connectionString = CONNECTION_STRING;
-    ConfigurationBuilder.overlayFromEnv(
-        configuration, Paths.get("."), System::getenv, System::getProperty);
-    assertThat(configuration.connectionString).isEqualTo(CONNECTION_STRING);
-  }
-
-  private static void assertFriendlyExceptionThrown(Configuration configuration, String filename) {
-    assertThatThrownBy(
-            () ->
-                ConfigurationBuilder.overlayFromEnv(
-                    configuration, Paths.get("."), System::getenv, System::getProperty))
-        .isInstanceOf(FriendlyException.class);
-    assertThat(configuration.connectionString).isEqualTo(filename);
-  }
-
   @Test
   void testConnectionStringEnvVarHasHigherPrecedenceOverFileLookup() throws Exception {
-    String testConnectionString = "test-connection-string";
+    String testConnectionString = "InstrumentationKey=00000000-0000-0000-0000-000000000000";
     envVars.put("APPLICATIONINSIGHTS_CONNECTION_STRING", testConnectionString);
 
     Configuration configuration = new Configuration();