“何时条件”检查的自定义衬里规则

Question

我使用Gson的序列化适配器RuntimeTypeAdapterFactory来序列化基于弟子的数据。但是，当有一个未解析的鉴别器(来自API)而没有在客户端上定义时，TypeAdapter将为空。

在这种情况下，如果我有一个kotlin当条件检查为：

when(fooType){
 is fooA -> //blaba
 is fooB -> //blaba
 //else or null is not handled
}

而fooType是null，当null条件不被处理时，它会崩溃。是否有任何方法可以创建自定义林特规则(检测器)，以便在条件(java中的实例)实现else或null检查并将其注入Android检查时检查？

Answer 1

我确实没有编写自定义皮棉检查的经验，但我认为这样的东西(虽然这不是最优的，而且您的不应该使用它，因为它只显示了它的想法)可能会奏效。

class WhenNullElseMissingDetector : Detector(), Detector.UastScanner {

    override fun getApplicableUastTypes(): MutableList<Class<out UElement>> =
        mutableListOf(USwitchExpression::class.java)

    override fun createUastHandler(context: JavaContext): UElementHandler = WhenNullElseMissingHandler(context)
}

class WhenNullElseMissingHandler(private val context: JavaContext) : UElementHandler() {

    override fun visitSwitchExpression(node: USwitchExpression) {
        if (node.psi?.javaClass != KtWhenExpression::class.java) {
            // returning early here, so it doesn't go false positive on java switches
            return
        }

        var hasNullClause = false
        var hasElseClause = false

        node.body.expressions.forEach { clause ->
             // checking the child's text here just for a example, you should
             // probably check if child's class is KtWhenConditionIsPattern,
             // KtWhenConditionWithExpression or LeafPsiElement
            val clauseText = clause.psi?.firstChild?.text

            if ("null" == clauseText) {
                hasNullClause = true
            } else if ("else" == clauseText) {
                hasElseClause = true
            }
        }

        if (!hasElseClause) {
            context.report(
                WHEN_NULL_OR_ELSE_MISSING, node, context.getLocation(node),
                "When expression must include an else case"
            )
        }

        if (!hasNullClause) {
            context.report(
                WHEN_NULL_OR_ELSE_MISSING, node, context.getLocation(node),
                "When expression must include a null case"
            )
        }
    }
}

当然，您必须将新的检测器添加到IssueRegistry中。假设您在一个单独的java/kotlin模块中检查了您的lint，它可能如下所示

package com.example.lintchecks

// omit imports

val WHEN_NULL_OR_ELSE_MISSING = Issue.create(
    "MY_ISSUE_ID",
    "A brief to show in a one line popup",
    "More detailed explanation",
    Category.CORRECTNESS,
    5,
    Severity.WARNING,
    Implementation(
        WhenNullElseMissingDetector::class.java,
        Scope.JAVA_FILE_SCOPE
    )
)

class MyIssueRegistry : IssueRegistry() {
    override val issues: List<Issue>
        get() = listOf(WHEN_NULL_OR_ELSE_MISSING)

}

库模块的build.gradle文件应该具有com.android.tools.lint:lint-api:26.4.0 (或与其相关的任何版本) compileOnly依赖项和如下所示的块

jar {
    manifest {
        attributes("Lint-Registry-v2": "com.example.lintchecks.MyIssueRegistry")
    }
}