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kotlinc -Werror ./app/src/main/java/com/example/compileroptionssample/Simple.kt error: warnings found and -Werror specified app/src/main/java/com/example/compileroptionssample/Simple.kt:4:19: warning: unnecessary safe call on a non-null receiver of type String println(string?.toString()) ^

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kotlinc -help Usage: kotlinc-jvm <options> <source files> where possible options include: -classpath (-cp) <path> Paths where to find user class files -d <directory|jar> Destination for generated class files -include-runtime Include Kotlin runtime in to resulting .jar -java-parameters Generate metadata for Java 1.8 reflection on method parameters -jdk-home <path> Path to JDK home directory to include into classpath, if differs from default JAVA_HOME -jvm-target <version> Target version of the generated JVM bytecode (1.6 or 1.8), default is 1.6 -module-name <name> Name of the generated .kotlin_module file -no-jdk Don't include Java runtime into classpath -no-reflect Don't include kotlin-reflect.jar into classpath -no-stdlib Don't include kotlin-stdlib.jar or kotlin-reflect.jar into classpath -script Evaluate the script file -script-templates <fully qualified class name[,]> Script definition template classes -Werror Report an error if there are any warnings -api-version <version> Allow to use declarations only from the specified version of bundled libraries -X Print a synopsis of advanced options -help (-h) Print a synopsis of standard options -kotlin-home <path> Path to Kotlin compiler home directory, used for runtime libraries discovery -language-version <version> Provide source compatibility with specified language version -P plugin:<pluginId>:<optionName>=<value> Pass an option to a plugin -progressive Enable progressive compiler mode. In this mode, deprecations and bug fixes for unstable code take effect immediately, instead of going through a graceful migration cycle. Code written in the progressive mode is backward compatible; however, code written in non-progressive mode may cause compilation errors in the progressive mode. -nowarn Generate no warnings -verbose Enable verbose logging output -version Display compiler version @<argfile> Expand compiler arguments from the given file, containing one argument or file path per line

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kotlinc -X Usage: kotlinc-jvm <options> <source files> where advanced options include: -Xadd-compiler-builtins Add definitions of built-in declarations to the compilation classpath (useful with -no-stdlib) -Xadd-modules=<module[,]> Root modules to resolve in addition to the initial modules, or all modules on the module path if <module> is ALL-MODULE-PATH -Xassertions={always-enable|always-disable|jvm|legacy} Assert calls behaviour -Xassertions=always-enable: enable, ignore jvm assertion settings; -Xassertions=always-disable: disable, ignore jvm assertion settings; -Xassertions=jvm: enable, depend on jvm assertion settings; -Xassertions=legacy: calculate condition on each call, check depends on jvm assertion settings in the kotlin package; default: legacy -Xbuild-file=<path> Path to the .xml build file to compile -Xcompile-java Reuse javac analysis and compile Java source files -Xnormalize-constructor-calls={disable|enable} Normalize constructor calls (disable: don't normalize; enable: normalize), default is 'disable' in language version 1.2 and below, 'enable' since language version 1.3 -Xdump-declarations-to=<path> Path to JSON file to dump Java to Kotlin declaration mappings -Xdisable-default-scripting-plugin Do not enable scripting plugin by default -Xdisable-standard-script Disable standard kotlin script support -Xfriend-paths=<path> Paths to output directories for friend modules (whose internals should be visible) -Xmultifile-parts-inherit Compile multifile classes as a hierarchy of parts and facade -Xmodule-path=<path> Paths where to find Java 9+ modules -Xjavac-arguments=<option[,]> Java compiler arguments -Xjsr305={ignore/strict/warn}|under-migration:{ignore/strict/warn}|@<fq.name>:{ignore/strict/warn} Specify behavior for JSR-305 nullability annotations: -Xjsr305={ignore/strict/warn} globally (all [email protected] annotations) -Xjsr305=under-migration:{ignore/strict/warn} all @UnderMigration annotations [email protected]<fq.name>:{ignore/strict/warn} annotation with the given fully qualified class name Modes: * ignore * strict (experimental; treat as other supported nullability annotations) * warn (report a warning) -Xjvm-default={disable|enable|compatibility} Allow to use '@JvmDefault' annotation for JVM default method support. -Xjvm-default=disable Prohibit usages of @JvmDefault -Xjvm-default=enable Allow usages of @JvmDefault; only generate the default method in the interface (annotating an existing method can break binary compatibility) -Xjvm-default=compatibility Allow usages of @JvmDefault; generate a compatibility accessor in the 'DefaultImpls' class in addition to the interface method -Xload-builtins-from-dependencies Load definitions of built-in declarations from module dependencies, instead of from the compiler -Xno-call-assertions Don't generate not-null assertions for arguments of platform types -Xno-exception-on-explicit-equals-for-boxed-null Do not throw NPE on explicit 'equals' call for null receiver of platform boxed primitive type -Xno-optimize Disable optimizations -Xno-param-assertions Don't generate not-null assertions on parameters of methods accessible from Java -Xno-receiver-assertions Don't generate not-null assertion for extension receiver arguments of platform types -Xsanitize-parentheses Transform '(' and ')' in method names to some other character sequence. This mode can BREAK BINARY COMPATIBILITY and is only supposed to be used as a workaround of an issue in the ASM bytecode framework. See KT-29475 for more details -Xscript-resolver-environment=<key=value[,]> Script resolver environment in key-value pairs (the value could be quoted and escaped) -Xsingle-module Combine modules for source files and binary dependencies into a single module -Xskip-runtime-version-check Allow Kotlin runtime libraries of incompatible versions in the classpath -Xstrict-java-nullability-assertions Generate nullability assertions for non-null Java expressions -Xgenerate-strict-metadata-version Generate metadata with strict version semantics (see kdoc on Metadata.extraInt) -Xsupport-compatqual-checker-framework-annotations=enable|disable Specify behavior for Checker Framework compatqual annotations (NullableDecl/NonNullDecl). Default value is 'enable' -Xuse-ir Use the IR backend -Xuse-javac Use javac for Java source and class files analysis -Xuse-old-class-files-reading Use old class files reading implementation. This may slow down the build and cause problems with Groovy interop. Should be used in case of problems with the new implementation -Xuse-type-table Use type table in metadata serialization -Xallow-kotlin-package Allow compiling code in package 'kotlin' and allow not requiring kotlin.stdlib in module-info -Xallow-result-return-type Allow compiling code when `kotlin.Result` is used as a return type -Xcommon-sources=<path> Sources of the common module that need to be compiled together with this module in the multi-platform mode. Should be a subset of sources passed as free arguments -Xcoroutines={enable|warn|error} Enable coroutines or report warnings or errors on declarations and use sites of 'suspend' modifier -Xdisable-phases Disable backend phases -Xdump-perf=<path> Dump detailed performance statistics to the specified file -Xeffect-system Enable experimental language feature: effect system -Xexperimental=<fq.name> Enable and propagate usages of experimental API for marker annotation with the given fully qualified name -Xintellij-plugin-root=<path> Path to the kotlin-compiler.jar or directory where IntelliJ configuration files can be found -Xlegacy-smart-cast-after-try Allow var smart casts despite assignment in try block -Xlist-phases List backend phases -Xmetadata-version Change metadata version of the generated binary files -Xmulti-platform Enable experimental language support for multi-platform projects -Xnew-inference Enable new experimental generic type inference algorithm -Xno-check-actual Do not check presence of 'actual' modifier in multi-platform projects -Xno-inline Disable method inlining -Xphases-to-dump Dump backend state both before and after these phases -Xphases-to-dump-after Dump backend state after these phases -Xphases-to-dump-before Dump backend state before these phases -Xplugin=<path> Load plugins from the given classpath -Xprofile-phases Profile backend phases -Xproper-ieee754-comparisons Generate proper IEEE 754 comparisons in all cases if values are statically known to be of primitive numeric types -Xread-deserialized-contracts Enable reading of contracts from metadata -Xreport-output-files Report source to output files mapping -Xreport-perf Report detailed performance statistics -Xskip-metadata-version-check Load classes with bad metadata version anyway (incl. pre-release classes) -Xuse-experimental=<fq.name> Enable, but don't propagate usages of experimental API for marker annotation with the given fully qualified name -Xverbose-phases Be verbose while performing these backend phases Advanced options are non-standard and may be changed or removed without any notice.

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android { compileSdkVersion 28 defaultConfig { applicationId "com.example.compileroptionssample" minSdkVersion 15 targetSdkVersion 28 versionCode 1 versionName "1.0" testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner" } buildTypes { release { minifyEnabled false proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro' } debug { } } //Code to be added kotlinOptions { allWarningsAsErrors = true } }

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kotlinOptions { allWarningsAsErrors = true freeCompilerArgs += ['-Xno-param-assertions', '-Xmultifile-parts-inherit'] }

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package com.example.compileroptionssample fun dump(string: String) { println(string) }

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//only add kotlinOptions for the releaseKotlin build task tasks.withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile).all { task -> if (task.getName() == "compileReleaseKotlin") { kotlinOptions { allWarningsAsErrors = true } println("Add kotlin options when task=" + task) } else { println("Do not add kotlin options when task=" + task) } }