WRONG_INDENTATION: add the test which reproduces the regression

### What's done:

 * See #1490.

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/chapter3/spaces/ExpectedIndentationError.kt

@@ -1,18 +1,50 @@
 package org.cqfn.diktat.ruleset.chapter3.spaces
 
+import org.cqfn.diktat.common.config.rules.DIKTAT_RULE_SET_ID
+import org.cqfn.diktat.ruleset.constants.Warnings.WRONG_INDENTATION
 import org.cqfn.diktat.ruleset.junit.ExpectedLintError
+import org.cqfn.diktat.ruleset.rules.chapter3.files.IndentationRule.Companion.NAME_ID
+import com.pinterest.ktlint.core.LintError
 
 /**
  * The expected indentation error (extracted from annotated code fragments).
  *
  * @property line the line number (1-based).
  * @property column the column number (1-based).
- * @property expectedIndent the expected indentation level (in space characters).
- * @property actualIndent the actual indentation level (in space characters).
  */
-data class ExpectedIndentationError(
-    override val line: Int,
-    override val column: Int = 1,
-    val expectedIndent: Int,
-    val actualIndent: Int
-) : ExpectedLintError
+class ExpectedIndentationError(override val line: Int,
+                               override val column: Int = 1,
+                               private val message: String
+) : ExpectedLintError {
+    /**
+     * @param line the line number (1-based).
+     * @param column the column number (1-based).
+     * @param expectedIndent the expected indentation level (in space characters).
+     * @param actualIndent the actual indentation level (in space characters).
+     */
+    constructor(line: Int,
+                column: Int = 1,
+                expectedIndent: Int,
+                actualIndent: Int
+    ) : this(
+        line,
+        column,
+        warnText(expectedIndent)(actualIndent)
+    )
+
+    override fun asLintError(): LintError =
+        LintError(
+            line,
+            column,
+            "$DIKTAT_RULE_SET_ID:$NAME_ID",
+            message,
+            true)
+
+    private companion object {
+        private val warnText: (Int) -> (Int) -> String = { expectedIndent ->
+            { actualIndent ->
+                "${WRONG_INDENTATION.warnText()} expected $expectedIndent but was $actualIndent"
+            }
+        }
+    }
+}

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/chapter3/spaces/IndentationRuleTest.kt

@@ -255,6 +255,22 @@ class IndentationRuleTest {
         fun `case 10`() = Unit
     }
 
+    @Nested
+    @TestMethodOrder(NaturalDisplayName::class)
+    inner class `String templates` {
+        /**
+         * See [#1490](https://github.com/saveourtool/diktat/issues/1490).
+         */
+        @IndentationTest(IndentedSourceCode(
+            """
+            val value = f(
+                "text ${'$'}variable text".isEmpty() // diktat:WRONG_INDENTATION[message = only spaces are allowed for indentation and each indentation should equal to 4 spaces (tabs are not allowed): the same number of indents to the opening and closing quotes was expected]
+            )
+            """),
+            singleConfiguration = true)
+        fun `issue #1490`() = Unit
+    }
+
     /**
      * See [#1347](https://github.com/saveourtool/diktat/issues/1347).
      */

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/chapter3/spaces/junit/IndentationTest.kt

@@ -9,8 +9,11 @@ import kotlin.annotation.AnnotationTarget.FUNCTION
 
 /**
  * @property includeWarnTests whether unit tests for the "warn" mode should also
- *   be generated. If `false`, only fix mode tests get generated. The default is
- *   `true`.
+ *   be generated. If `false`, the code is allowed to have no expected-error
+ *   annotations, and only fix mode tests get generated. The default is `true`.
+ * @property singleConfiguration whether only a single code fragment is to be
+ *   analysed. If `true`, the value of [second] is ignored, resulting in fewer
+ *   unit tests being generated. The default is `false`.
  */
 @Target(FUNCTION)
 @Retention(RUNTIME)
@@ -20,6 +23,7 @@ import kotlin.annotation.AnnotationTarget.FUNCTION
 @Tag(WRONG_INDENTATION)
 annotation class IndentationTest(
     val first: IndentedSourceCode,
-    val second: IndentedSourceCode,
-    val includeWarnTests: Boolean = true
+    val second: IndentedSourceCode = IndentedSourceCode(""),
+    val includeWarnTests: Boolean = true,
+    val singleConfiguration: Boolean = false,
 )

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/chapter3/spaces/junit/IndentationTestInvocationContextProvider.kt

@@ -34,6 +34,14 @@ class IndentationTestInvocationContextProvider : RuleInvocationContextProvider<I
         tag: String,
         properties: Map<String, String?>
     ): ExpectedIndentationError {
+        val message = properties[MESSAGE]
+        @Suppress("AVOID_NULL_CHECKS")
+        if (message != null) {
+            return ExpectedIndentationError(
+                line = lineNumber,
+                message = "[$WRONG_INDENTATION] $message")
+        }
+
         val expectedIndent = properties.expectedIndent()
         val actualIndent = line.leadingSpaceCount()
 
@@ -58,57 +66,81 @@ class IndentationTestInvocationContextProvider : RuleInvocationContextProvider<I
         val indentationTest = findAnnotation(testMethod, annotationType().java).get()
 
         val includeWarnTests = indentationTest.includeWarnTests
+        val singleConfiguration = indentationTest.singleConfiguration
 
-        val testInput0 = indentationTest.first.extractTestInput(supportedTags, includeWarnTests)
+        val testInput0 = indentationTest.first.extractTestInput(
+            supportedTags,
+            allowEmptyErrors = !includeWarnTests || singleConfiguration)
         val (code0, expectedErrors0, customConfig0) = testInput0
 
-        val testInput1 = indentationTest.second.extractTestInput(supportedTags, includeWarnTests)
-        val (code1, expectedErrors1, customConfig1) = testInput1
-
-        assertThat(code0)
-            .describedAs("Both code fragments are the same")
-            .isNotEqualTo(code1)
-        assertThat(customConfig0)
-            .describedAs("Both custom configs are the same")
-            .isNotEqualTo(customConfig1)
-        assertThat(testInput0.effectiveConfig)
-            .describedAs("Both effective configs are the same")
-            .isNotEqualTo(testInput1.effectiveConfig)
-
-        return Stream.of<TestTemplateInvocationContext>(
-            IndentationTestFixInvocationContext(customConfig0, actualCode = code0),
-            IndentationTestFixInvocationContext(customConfig1, actualCode = code1),
-            IndentationTestFixInvocationContext(customConfig1, actualCode = code0, expectedCode = code1),
-            IndentationTestFixInvocationContext(customConfig0, actualCode = code1, expectedCode = code0),
-        ).let { fixTests ->
-            when {
-                includeWarnTests -> concat(fixTests, Stream.of(
-                    IndentationTestWarnInvocationContext(customConfig0, actualCode = code0),
-                    IndentationTestWarnInvocationContext(customConfig1, actualCode = code1),
-                    IndentationTestWarnInvocationContext(customConfig1, actualCode = code0, expectedErrors0),
-                    IndentationTestWarnInvocationContext(customConfig0, actualCode = code1, expectedErrors1),
-                ))
-
-                else -> fixTests
+        var contexts: Stream<TestTemplateInvocationContext> = Stream.of(
+            IndentationTestFixInvocationContext(customConfig0, actualCode = code0)
+        )
+
+        if (includeWarnTests) {
+            /*-
+             * In a double-configuration mode (the default), when the code is
+             * checked against its own configuration, the actual list of errors
+             * is expected to be empty (it's only used when the code is checked
+             * against the opposite configuration.
+             *
+             * In a single-configuration mode, the opposite configuration is
+             * empty, so let's allow a non-empty list of expected errors when
+             * the code is checked against its own configuration.
+             */
+            val expectedErrors = when {
+                singleConfiguration -> expectedErrors0
+                else -> emptyList()
+            }
+            contexts += IndentationTestWarnInvocationContext(customConfig0, actualCode = code0, expectedErrors)
+        }
+
+        if (!singleConfiguration) {
+            val testInput1 = indentationTest.second.extractTestInput(
+                supportedTags,
+                allowEmptyErrors = !includeWarnTests)
+            val (code1, expectedErrors1, customConfig1) = testInput1
+
+            assertThat(code0)
+                .describedAs("Both code fragments are the same")
+                .isNotEqualTo(code1)
+            assertThat(customConfig0)
+                .describedAs("Both custom configs are the same")
+                .isNotEqualTo(customConfig1)
+            assertThat(testInput0.effectiveConfig)
+                .describedAs("Both effective configs are the same")
+                .isNotEqualTo(testInput1.effectiveConfig)
+
+            contexts += IndentationTestFixInvocationContext(customConfig1, actualCode = code1)
+            contexts += IndentationTestFixInvocationContext(customConfig1, actualCode = code0, expectedCode = code1)
+            contexts += IndentationTestFixInvocationContext(customConfig0, actualCode = code1, expectedCode = code0)
+
+            if (includeWarnTests) {
+                contexts += IndentationTestWarnInvocationContext(customConfig1, actualCode = code1)
+                contexts += IndentationTestWarnInvocationContext(customConfig1, actualCode = code0, expectedErrors0)
+                contexts += IndentationTestWarnInvocationContext(customConfig0, actualCode = code1, expectedErrors1)
             }
-        }.sorted { left, right ->
+        }
+
+        return contexts.sorted { left, right ->
             left.getDisplayName(0).compareTo(right.getDisplayName(0))
         }
     }
 
     /**
-     * @param includeWarnTests whether unit tests for the "warn" mode should also
-     *   be generated. If `false`, only fix mode tests get generated.
+     * @param allowEmptyErrors whether the list of expected errors is allowed to
+     *   be empty (i.e. the code may contain no known annotations).
      */
     private fun IndentedSourceCode.extractTestInput(supportedTags: List<String>,
-                                                    includeWarnTests: Boolean): IndentationTestInput {
-        val (code, expectedErrors) = extractExpectedErrors(code, supportedTags, includeWarnTests)
+                                                    allowEmptyErrors: Boolean): IndentationTestInput {
+        val (code, expectedErrors) = extractExpectedErrors(code, supportedTags, allowEmptyErrors)
 
         return IndentationTestInput(code, expectedErrors, customConfig())
     }
 
     private companion object {
         private const val EXPECTED_INDENT = "expectedIndent"
+        private const val MESSAGE = "message"
 
         @Suppress("WRONG_NEWLINES")  // False positives, see #1495.
         private fun IndentedSourceCode.customConfig(): SortedMap<String, out Boolean> =
@@ -140,5 +172,8 @@ class IndentationTestInvocationContextProvider : RuleInvocationContextProvider<I
                 fail("Unparseable `$EXPECTED_INDENT`: $expectedIndentRaw")
             }
         }
+
+        private operator fun <T> Stream<T>.plus(value: T): Stream<T> =
+            concat(this, Stream.of(value))
     }
 }

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/chapter3/spaces/junit/IndentationTestWarnExtension.kt

@@ -37,9 +37,17 @@ internal class IndentationTestWarnExtension(
         val description = NEWLINE + actualCode.annotateWith(actualErrors) + NEWLINE
 
         when {
-            expectedErrors.size == 1 && actualErrors.size == 1 -> assertThat(actualErrors[0])
-                .describedAs(description)
-                .isEqualTo(expectedErrors[0])
+            expectedErrors.size == 1 && actualErrors.size == 1 -> {
+                val actual = actualErrors[0]
+                val expected = expectedErrors[0]
+
+                assertThat(actual)
+                    .describedAs(description)
+                    .isEqualTo(expected)
+                assertThat(actual.canBeAutoCorrected)
+                    .describedAs("canBeAutoCorrected")
+                    .isEqualTo(expected.canBeAutoCorrected)
+            }
 
             else -> assertThat(actualErrors)
                 .describedAs(description)

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/chapter3/spaces/junit/IndentationTestWarnInvocationContext.kt

@@ -1,10 +1,7 @@
 package org.cqfn.diktat.ruleset.chapter3.spaces.junit
 
-import org.cqfn.diktat.common.config.rules.DIKTAT_RULE_SET_ID
 import org.cqfn.diktat.ruleset.chapter3.spaces.ExpectedIndentationError
-import org.cqfn.diktat.ruleset.constants.Warnings.WRONG_INDENTATION
-import org.cqfn.diktat.ruleset.rules.chapter3.files.IndentationRule.Companion.NAME_ID
-import com.pinterest.ktlint.core.LintError
+import org.cqfn.diktat.ruleset.junit.ExpectedLintError
 import org.intellij.lang.annotations.Language
 import org.junit.jupiter.api.extension.Extension
 import java.util.SortedMap
@@ -36,25 +33,5 @@ internal class IndentationTestWarnInvocationContext(
         listOf(IndentationTestWarnExtension(
             customConfig,
             actualCode,
-            expectedErrors.map(asLintError).toTypedArray()))
-
-    private companion object {
-        private val warnText: (Int) -> (Int) -> String = { expectedIndent ->
-            { actualIndent ->
-                "${WRONG_INDENTATION.warnText()} expected $expectedIndent but was $actualIndent"
-            }
-        }
-
-        /**
-         * Converts this instance to a [LintError].
-         */
-        private val asLintError: ExpectedIndentationError.() -> LintError = {
-            LintError(
-                line,
-                column,
-                "$DIKTAT_RULE_SET_ID:$NAME_ID",
-                warnText(expectedIndent)(actualIndent),
-                true)
-        }
-    }
+            expectedErrors.map(ExpectedLintError::asLintError).toTypedArray()))
 }

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/junit/ExpectedLintError.kt

@@ -1,5 +1,7 @@
 package org.cqfn.diktat.ruleset.junit
 
+import com.pinterest.ktlint.core.LintError
+
 /**
  * The common super-interface for expected lint errors (extracted from the
  * annotated code).
@@ -14,4 +16,11 @@ interface ExpectedLintError {
      * The column number (1-based).
      */
     val column: Int
+
+    /**
+     * Converts this instance to a [LintError].
+     *
+     * @return the [LintError] which corresponds to this instance.
+     */
+    fun asLintError(): LintError
 }

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/junit/RuleInvocationContextProvider.kt

@@ -76,15 +76,15 @@ interface RuleInvocationContextProvider<A : Annotation, out E : ExpectedLintErro
      * @param code the annotated code.
      * @param supportedTags the list of check names that should be recognized
      *   (implementation-dependent).
-     * @param includeWarnTests whether unit tests for the "warn" mode should also
-     *   be generated. If `false`, only fix mode tests get generated.
+     * @param allowEmptyErrors whether the list of expected errors is allowed to
+     *   be empty (i.e. the code may contain no known annotations).
      * @return the list of expected errors as well as the filtered code.
      * @see expectedLintErrorFrom
      */
     @Suppress("TOO_LONG_FUNCTION")
     fun extractExpectedErrors(@Language("kotlin") code: String,
                               supportedTags: List<String>,
-                              includeWarnTests: Boolean
+                              allowEmptyErrors: Boolean
     ): ExpectedLintErrors<E> {
         require(supportedTags.isNotEmpty()) {
             "The list of supported tags is empty"
@@ -120,7 +120,7 @@ interface RuleInvocationContextProvider<A : Annotation, out E : ExpectedLintErro
             1 -> supportedTags[0]
             else -> "any of $supportedTags"
         }
-        if (includeWarnTests) {
+        if (!allowEmptyErrors) {
             assertThat(expectedErrors)
                 .describedAs("The code contains no expected-error annotations or an unsupported tag is used (should be $supportedTagsDescription). " +
                         "Please annotate your code or set `includeWarnTests` to `false`:$NEWLINE$filteredCode")
@@ -177,7 +177,7 @@ interface RuleInvocationContextProvider<A : Annotation, out E : ExpectedLintErro
         private const val TAG = "tag"
 
         @Language("RegExp")
-        private const val VALUE = """[^,\h]*"""
+        private const val VALUE = """[^,\]]*?"""
         private const val VALUE_GROUP = "value"
         private val entryRegex = Regex("""\h*(?<$KEY_GROUP>$KEY)\h*=\h*(?<$VALUE_GROUP>$VALUE)\h*""")
 

diktat-rules/src/test/kotlin/org/cqfn/diktat/util/LintTestBase.kt

@@ -33,9 +33,17 @@ open class LintTestBase(private val ruleSupplier: (rulesConfigList: List<RulesCo
         val description = "lint result for \"$code\""
 
         when {
-            expectedLintErrors.size == 1 && actualLintErrors.size == 1 -> assertThat(actualLintErrors[0])
-                .describedAs(description)
-                .isEqualTo(expectedLintErrors[0])
+            expectedLintErrors.size == 1 && actualLintErrors.size == 1 -> {
+                val actual = actualLintErrors[0]
+                val expected = expectedLintErrors[0]
+
+                assertThat(actual)
+                    .describedAs(description)
+                    .isEqualTo(expected)
+                assertThat(actual.canBeAutoCorrected)
+                    .describedAs("canBeAutoCorrected")
+                    .isEqualTo(expected.canBeAutoCorrected)
+            }
 
             else -> assertThat(actualLintErrors)
                 .describedAs(description)