add dev mode where warnings don't fail the test (#11273)

Co-authored-by: Trask Stalnaker <trask.stalnaker@gmail.com>

conventions/src/main/kotlin/otel.java-conventions.gradle.kts

@@ -72,12 +72,13 @@ tasks.withType<JavaCompile>().configureEach {
           // We suppress the "options" warning because it prevents compilation on modern JDKs
           "-Xlint:-options",
           // jdk21 generates more serial warnings than previous versions
-          "-Xlint:-serial",
-
-          // Fail build on any warning
-          "-Werror"
+          "-Xlint:-serial"
         )
       )
+      if (System.getProperty("dev") != "true") {
+        // Fail build on any warning
+        compilerArgs.add("-Werror")
+      }
     }
 
     encoding = "UTF-8"

docs/contributing/running-tests.md

@@ -38,6 +38,18 @@ To run these tests locally, add `-PtestLatestDeps=true` to your existing `gradle
 
 Executing `./gradlew :instrumentation:<INSTRUMENTATION_NAME>:test --tests <GROOVY TEST FILE NAME>` will run only the selected test.
 
+### How to prevent linting and formatting warnings from failing tests
+
+During local development, you may want to ignore lint warnings when running tests.
+
+To ignore warnings, formatting issues, or other non-fatal issues in tests, use
+
+```
+./gradlew test -Ddev=true -x spotlessCheck -x checkstyleMain
+```
+
+The `dev` flag will ignore warnings in tests.
+
 ## Smoke tests
 
 The smoke tests are not run as part of a global `test` task run since they take a long time and are