override fun visitFile()

in rules/common/src/main/kotlin/com/twitter/compose/rules/ComposeMultipleContentEmitters.kt [18:64]
28 lines of code
3 McCabe index (conditional complexity)

    override fun visitFile(file: KtFile, autoCorrect: Boolean, emitter: Emitter) {
        // CHECK #1 : We want to find the composables first that are at risk of emitting content from multiple sources.
        val composables = file.findChildrenByClass<KtFunction>()
            .filter { it.isComposable }
            // We don't want to analyze composables that are extension functions, as they might be things like
            // BoxScope which are legit, and we want to avoid false positives.
            .filter { it.hasBlockBody() }
            // We want only methods with a body
            .filterNot { it.hasReceiverType }

        // Now we want to get the count of direct emitters in them: the composables we know for a fact that output UI
        val composableToEmissionCount = composables.associateWith { it.directUiEmitterCount }

        // We can start showing errors, for composables that emit more than once (from the list of known composables)
        val directEmissionsReported = composableToEmissionCount.filterValues { it > 1 }.keys
        for (composable in directEmissionsReported) {
            emitter.report(composable, MultipleContentEmittersDetected)
        }

        // Now we can give some extra passes through the list of composables, and try to get a more accurate count.
        // We want to make sure that if these composables are using other composables in this file that emit UI,
        // those are taken into account too. For example:
        // @Composable fun Comp1() { Text("Hi") }
        // @Composable fun Comp2() { Text("Hola") }
        // @Composable fun Comp3() { Comp1() Comp2() } // This wouldn't be picked up at first, but should after 1 loop
        var currentMapping = composableToEmissionCount

        var shouldMakeAnotherPass = true
        while (shouldMakeAnotherPass) {
            val updatedMapping = currentMapping.mapValues { (functionNode, _) ->
                functionNode.indirectUiEmitterCount(currentMapping)
            }
            when {
                updatedMapping != currentMapping -> currentMapping = updatedMapping
                else -> shouldMakeAnotherPass = false
            }
        }

        // Here we have the settled data after all the needed passes, so we want to show errors for them,
        // if they were not caught already by the 1st emission loop
        currentMapping.filterValues { it > 1 }
            .filterNot { directEmissionsReported.contains(it.key) }
            .keys
            .forEach { composable ->
                emitter.report(composable, MultipleContentEmittersDetected)
            }
    }