Add StringShouldBeRawString.kt rule

detekt-core/src/main/resources/default-detekt-config.yml

@@ -662,6 +662,10 @@ style:
     active: true
   SpacingBetweenPackageAndImports:
     active: false
+  StringShouldBeRawString:
+    active: false
+    maxEscapedCharacterCount: 2
+    ignoredCharacters: []
   ThrowsCount:
     active: true
     max: 2

detekt-rules-style/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/style/StringShouldBeRawString.kt

@@ -0,0 +1,157 @@
+package io.gitlab.arturbosch.detekt.rules.style
+
+import io.gitlab.arturbosch.detekt.api.CodeSmell
+import io.gitlab.arturbosch.detekt.api.Config
+import io.gitlab.arturbosch.detekt.api.Debt
+import io.gitlab.arturbosch.detekt.api.Entity
+import io.gitlab.arturbosch.detekt.api.Issue
+import io.gitlab.arturbosch.detekt.api.Rule
+import io.gitlab.arturbosch.detekt.api.Severity
+import io.gitlab.arturbosch.detekt.api.config
+import io.gitlab.arturbosch.detekt.api.internal.Configuration
+import org.jetbrains.kotlin.com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.psi.KtBinaryExpression
+import org.jetbrains.kotlin.psi.KtElement
+import org.jetbrains.kotlin.psi.KtExpression
+import org.jetbrains.kotlin.psi.KtParenthesizedExpression
+import org.jetbrains.kotlin.psi.KtStringTemplateExpression
+import org.jetbrains.kotlin.psi.psiUtil.getParentOfTypesAndPredicate
+import org.jetbrains.kotlin.psi2ir.deparenthesize
+
+/**
+ * This rule reports when the string can be converted to Kotlin raw string.
+ * Usage of a raw string is preferred as that avoids the need for escaping strings escape characters like \n, \t, ".
+ * Raw string also allows us to represent multiline string without the need of \n.
+ * Also, see [Kotlin coding convention](https://kotlinlang.org/docs/coding-conventions.html#strings)  for
+ * recommendation on using multiline strings
+ *
+ * <noncompliant>
+ * val windowJson = "{\n" +
+ *                  "  \"window\": {\n" +
+ *                  "    \"title\": \"Sample Quantum With AI and ML Widget\",\n" +
+ *                  "    \"name\": \"main_window\",\n" +
+ *                  "    \"width\": 500,\n" +
+ *                  "    \"height\": 500\n" +
+ *                  "  }\n" +
+ *                  "}"
+ *
+ * val patRegex = "/^(\\/[^\\/]+){0,2}\\/?\$/gm\n"
+ * </noncompliant>
+ *
+ * <compliant>
+ * val windowJson = """
+ *     {
+ *          "window": {
+ *              "title": "Sample Quantum With AI and ML Widget",
+ *              "name": "main_window",
+ *              "width": 500,
+ *              "height": 500
+ *          }
+ *     }
+ * """.trimMargin()
+ *
+ * val patRegex = """/^(\/[^\/]+){0,2}\/?$/gm"""
+ * </compliant>
+ */
+class StringShouldBeRawString(config: Config) : Rule(config) {
+    override val issue = Issue(
+        javaClass.simpleName,
+        Severity.Style,
+        "The string can be converted to raw string.",
+        Debt.FIVE_MINS,
+    )
+
+    @Configuration("maximum escape characters allowed")
+    private val maxEscapedCharacterCount by config(2)
+
+    @Configuration("list of characters to ignore")
+    private val ignoredCharacters by config(emptyList<String>())
+
+    private val KtElement.leftMostElementOfLeftSubtree: KtElement
+        get() {
+            val leftChild = (this as? KtBinaryExpression)?.left?.deparenthesize() ?: return this
+            return leftChild.leftMostElementOfLeftSubtree
+        }
+
+    private val KtElement.rightMostElementOfRightSubtree: KtElement
+        get() {
+            val leftChild = (this as? KtBinaryExpression)?.right?.deparenthesize() ?: return this
+            return leftChild.rightMostElementOfRightSubtree
+        }
+
+    override fun visitStringTemplateExpression(expression: KtStringTemplateExpression) {
+        super.visitStringTemplateExpression(expression)
+        val expressionParent = expression.getParentExpressionAfterParenthesis()
+        val rootElement = expression.getRootExpression()
+        if (
+            expressionParent !is KtBinaryExpression ||
+            (rootElement != null && expression.isPivotElementInTheTree(rootElement))
+        ) {
+            val stringSeqToProcess = rootElement?.getStringSequenceExcludingRawString() ?: sequenceOf("")
+            val hasNoViolations = stringSeqToProcess.flatMap { stringTemplateExpressionText ->
+                REGEX_FOR_ESCAPE_CHARS.findAll(stringTemplateExpressionText).filter {
+                    it.value !in ignoredCharacters
+                }
+            }.drop(maxEscapedCharacterCount).none()
+            if (hasNoViolations.not()) {
+                report(
+                    CodeSmell(
+                        issue,
+                        Entity.from(rootElement ?: expression),
+                        "String with escape characters should be converted to raw string",
+                    )
+                )
+            }
+        }
+    }
+
+    private fun KtStringTemplateExpression.isPivotElementInTheTree(
+        rootElement: KtElement,
+    ): Boolean {
+        val leftMostElementOfLeftSubtree = rootElement.leftMostElementOfLeftSubtree
+        return this == if (leftMostElementOfLeftSubtree is KtStringTemplateExpression) {
+            leftMostElementOfLeftSubtree
+        } else {
+            rootElement.rightMostElementOfRightSubtree
+        }
+    }
+
+    private fun KtElement.getStringSequenceExcludingRawString(): Sequence<String> {
+        fun KtElement.getStringSequence(): Sequence<KtStringTemplateExpression> = sequence {
+            if (this@getStringSequence is KtStringTemplateExpression) {
+                yield(this@getStringSequence)
+            } else if (this@getStringSequence is KtBinaryExpression) {
+                left?.let {
+                    yieldAll(it.deparenthesize().getStringSequence())
+                }
+                right?.let {
+                    yieldAll(it.deparenthesize().getStringSequence())
+                }
+            }
+        }
+        return this.getStringSequence().filter {
+            (it.text.startsWith("\"\"\"") && it.text.endsWith("\"\"\"")).not()
+        }.map {
+            it.text
+        }
+    }
+
+    private fun KtExpression.getParentExpressionAfterParenthesis(): PsiElement? =
+        this.getParentOfTypesAndPredicate(true, PsiElement::class.java) { it !is KtParenthesizedExpression }
+
+    private fun KtElement.getRootExpression(): KtElement? {
+        return this.getParentOfTypesAndPredicate(
+            false,
+            KtBinaryExpression::class.java,
+            KtParenthesizedExpression::class.java,
+            KtStringTemplateExpression::class.java,
+        ) {
+            val parent = (it as KtExpression).parent
+            parent !is KtBinaryExpression && parent !is KtParenthesizedExpression
+        }?.deparenthesize()
+    }
+
+    companion object {
+        private val REGEX_FOR_ESCAPE_CHARS = """\\[t"\\n]""".toRegex()
+    }
+}

detekt-rules-style/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/style/StyleGuideProvider.kt

@@ -97,6 +97,7 @@ class StyleGuideProvider : DefaultRuleSetProvider {
             UseIfEmptyOrIfBlank(config),
             MultilineLambdaItParameter(config),
             MultilineRawStringIndentation(config),
+            StringShouldBeRawString(config),
             UseIsNullOrEmpty(config),
             UseOrEmpty(config),
             UseAnyOrNoneInsteadOfFind(config),