Kotlin gradebook example

A multi-package Kotlin app. It has a gradebook CLI, a grades library that reads JSON through gson and groups students through guava, a generated BuildInfo object and a packaged grades.json resource.

bazel build //examples/kotlin-app/...
bazel test //examples/kotlin-app/...
bazel run //:dx -- generate --check //examples/kotlin-app/...
bazel run //examples/kotlin-app/cli:grades -- ranks
bazel run //examples/kotlin-app/cli:grades -- show ada
bazel run //examples/kotlin-app/cli:grades -- --file path/to/grades.json list

Without --file or GRADES_FILE, grades reads the grades.json packaged in the grades jar, so the binary runs from any directory. Relative --file paths resolve against the directory you ran bazel run from. Scores must be whole numbers from 0 to 100, and every student needs at least one.

dx generate owns the grades and cli libraries. Main.kt, tests and diagnostics stay handwritten.

Exit codes: 0 ok, 2 usage, 3 unreadable or malformed grade file, 4 unknown student. exit_codes_test runs the binary through each code.

gson and guava come from the locked @maven hub. classpath_test checks that the app classes load from the grades jar and the library classes from their own jars. Tests use JUnit 4. Kotlin warnings are errors.

format_test checks the sources against the pinned ktfmt in Kotlin-lang style. diagnostics_test compiles, lints and formats files with a syntax error, a type error, a compiler warning, a wildcard import and bad formatting, and expects each to fail. It also compiles the grades sources: they fail without gson or guava on the classpath and pass with both.