Use spotless for enforcing licenses

It's more verbose as the default license plugin doesn't support multiple license headers. However, it also gives us some other goodies (namely formatting Kotlin and removing unused imports), so worth doing.
2025-10-25 10:57:57 +00:00 · 2022-10-22 17:47:39 +01:00
parent 57cf6084e2
commit af5d816798
19 changed files with 179 additions and 51 deletions
--- a/buildSrc/src/main/kotlin/cc/tweaked/gradle/CheckLicense.kt
+++ b/buildSrc/src/main/kotlin/cc/tweaked/gradle/CheckLicense.kt
@@ -0,0 +1,73 @@
+package cc.tweaked.gradle
+
+import com.diffplug.spotless.FormatterFunc
+import com.diffplug.spotless.FormatterStep
+import com.diffplug.spotless.generic.LicenseHeaderStep
+import java.io.File
+import java.io.Serializable
+import java.nio.charset.StandardCharsets
+
+/**
+ * Similar to [LicenseHeaderStep], but supports multiple licenses.
+ */
+object LicenseHeader {
+    /**
+     * The current year to use in templates. Intentionally not dynamic to avoid failing the build.
+     */
+    private const val YEAR = 2022
+
+    private val COMMENT = Regex("""^/\*(.*?)\*/\n?""", RegexOption.DOT_MATCHES_ALL)
+
+    fun create(api: File, main: File): FormatterStep = FormatterStep.createLazy(
+        "license",
+        { Licenses(getTemplateText(api), getTemplateText(main)) },
+        { state -> FormatterFunc.NeedsFile { contents, file -> formatFile(state, contents, file) } },
+    )
+
+    private fun getTemplateText(file: File): String =
+        file.readText(StandardCharsets.UTF_8).trim().replace("\${year}", "$YEAR")
+
+    private fun formatFile(licenses: Licenses, contents: String, file: File): String {
+        val license = getLicense(contents)
+        val expectedLicense = getExpectedLicense(licenses, file.parentFile)
+
+        return when {
+            license == null -> setLicense(expectedLicense, contents)
+            license.second != expectedLicense -> setLicense(expectedLicense, contents, license.first)
+            else -> contents
+        }
+    }
+
+    private fun getExpectedLicense(licenses: Licenses, file: File): String {
+        var file: File? = file
+        while (file != null) {
+            if (file.name == "api" && file.parentFile?.name == "computercraft") return licenses.api
+            file = file.parentFile
+        }
+        return licenses.main
+    }
+
+    private fun getLicense(contents: String): Pair<Int, String>? {
+        val match = COMMENT.find(contents) ?: return null
+        val license = match.groups[1]!!.value
+            .trim().lineSequence()
+            .map { it.trimStart(' ', '*') }
+            .joinToString("\n")
+        return Pair(match.range.last + 1, license)
+    }
+
+    private fun setLicense(license: String, contents: String, start: Int = 0): String {
+        val out = StringBuilder()
+        out.append("/*\n")
+        for (line in license.lineSequence()) out.append(" * ").append(line).append("\n")
+        out.append(" */\n")
+        out.append(contents, start, contents.length)
+        return out.toString()
+    }
+
+    private data class Licenses(val api: String, val main: String) : Serializable {
+        companion object {
+            private const val serialVersionUID: Long = 7741106448372435662L
+        }
+    }
+}