Remove null argument checks and thrown ArgumentNullExceptions (#657)

* Remove ArgumentNullExceptions from CommandLineTool

* Remove ArgumentNullExceptions from CompilationManager

* Remove ArgumentNullExceptions from Compiler

* Remove ArgumentNullExceptions from LanguageServer

* Remove ArgumentNullExceptions in Transformations

* Fix null error

* Revert API change

Author: bamarsha

src/QsCompiler/CommandLineTool/Commands/Build.cs

@@ -152,14 +152,9 @@ private static IEnumerable<string> SplitCommandLineArguments(string commandLine)
         /// <summary>
         /// Reads the content off all given response files and tries to parse their concatenated content as command line arguments.
         /// Logs a suitable exceptions and returns null if the parsing fails.
-        /// Throws an ArgumentNullException if the given sequence of responseFiles is null.
         /// </summary>
         private static BuildOptions? FromResponseFiles(IEnumerable<string> responseFiles)
         {
-            if (responseFiles == null)
-            {
-                throw new ArgumentNullException(nameof(responseFiles));
-            }
             var commandLine = string.Join(" ", responseFiles.Select(File.ReadAllText));
             var args = SplitCommandLineArguments(commandLine);
             var parsed = Parser.Default.ParseArguments<BuildOptions>(args);
@@ -177,18 +172,9 @@ private static IEnumerable<string> SplitCommandLineArguments(string commandLine)
         /// <summary>
         /// Builds the compilation for the Q# code or Q# snippet and referenced assemblies defined by the given options.
         /// Returns a suitable error code if one of the compilation or generation steps fails.
-        /// Throws an ArgumentNullException if any of the given arguments is null.
         /// </summary>
         public static int Run(BuildOptions options, ConsoleLogger logger)
         {
-            if (options == null)
-            {
-                throw new ArgumentNullException(nameof(options));
-            }
-            if (logger == null)
-            {
-                throw new ArgumentNullException(nameof(logger));
-            }
             if (!BuildOptions.IncorporateResponseFiles(options, out var incorporated))
             {
                 logger.Log(ErrorCode.InvalidCommandLineArgsInResponseFiles, Array.Empty<string>());

src/QsCompiler/CommandLineTool/Commands/Diagnose.cs

@@ -78,14 +78,9 @@ public static IEnumerable<Example> UsageExamples
         /// Logs the content of each file in the given compilation as Information using the given logger.
         /// If the id of a file is consistent with the one assigned to a code snippet,
         /// strips the lines of code that correspond to the wrapping defined by WrapSnippet.
-        /// Throws an ArgumentNullException if the given compilation is null.
         /// </summary>
         private static void PrintFileContentInMemory(Compilation compilation, ILogger logger)
         {
-            if (compilation == null)
-            {
-                throw new ArgumentNullException(nameof(compilation));
-            }
             foreach (var file in compilation.SourceFiles)
             {
                 IEnumerable<string> inMemory = compilation.FileContent[file];
@@ -110,14 +105,9 @@ private static void PrintFileContentInMemory(Compilation compilation, ILogger lo
         /// Logs the tokenization of each file in the given compilation as Information using the given logger.
         /// If the id of a file is consistent with the one assigned to a code snippet,
         /// strips the tokens that correspond to the wrapping defined by WrapSnippet.
-        /// Throws an ArgumentNullException if the given compilation is null.
         /// </summary>
         private static void PrintContentTokenization(Compilation compilation, ILogger logger)
         {
-            if (compilation == null)
-            {
-                throw new ArgumentNullException(nameof(compilation));
-            }
             foreach (var file in compilation.SourceFiles)
             {
                 var tokenization = compilation.Tokenization[file].Select(tokens => tokens.Select(token => token.Kind));
@@ -152,14 +142,9 @@ private static void PrintContentTokenization(Compilation compilation, ILogger lo
         /// If the id of a file is consistent with the one assigned to a code snippet,
         /// strips the lines of code that correspond to the wrapping defined by WrapSnippet.
         /// Throws an ArgumentException if this is not possible because the given syntax tree is inconsistent with that wrapping.
-        /// Throws an ArgumentNullException if the given compilation is null.
         /// </summary>
         private static void PrintSyntaxTree(IEnumerable<QsNamespace>? evaluatedTree, Compilation compilation, ILogger logger)
         {
-            if (compilation == null)
-            {
-                throw new ArgumentNullException(nameof(compilation));
-            }
             evaluatedTree ??= compilation.SyntaxTree.Values;
 
             foreach (var file in compilation.SourceFiles)
@@ -191,14 +176,9 @@ void PrintTree(string serialization) => logger.Log(
         /// If the id of a file is consistent with the one assigned to a code snippet,
         /// strips the lines of code that correspond to the wrapping defined by WrapSnippet.
         /// Throws an ArgumentException if this is not possible because the given syntax tree is inconsistent with that wrapping.
-        /// Throws an ArgumentNullException if the given compilation is null.
         /// </summary>
         private static void PrintGeneratedQs(IEnumerable<QsNamespace>? evaluatedTree, Compilation compilation, ILogger logger)
         {
-            if (compilation == null)
-            {
-                throw new ArgumentNullException(nameof(compilation));
-            }
             evaluatedTree ??= compilation.SyntaxTree.Values;
 
             foreach (var file in compilation.SourceFiles)
@@ -224,14 +204,9 @@ private static void PrintGeneratedQs(IEnumerable<QsNamespace>? evaluatedTree, Co
         /// <summary>
         /// Strips the namespace and callable declaration that is consistent with the wrapping defined by WrapSnippet.
         /// Throws an ArgumentException if this is not possible because the given syntax tree is inconsistent with that wrapping.
-        /// Throws an ArgumentNullException if the given syntaxTree is null.
         /// </summary>
         public static IEnumerable<QsStatement> StripSnippetWrapping(IEnumerable<QsNamespace> syntaxTree)
         {
-            if (syntaxTree == null)
-            {
-                throw new ArgumentNullException(nameof(syntaxTree));
-            }
             var incorrectWrapperException = new ArgumentException("syntax tree does not reflect the expected wrapper");
             if (syntaxTree.Count() != 1 || syntaxTree.Single().Elements.Count() != 1)
             {
@@ -253,19 +228,9 @@ public static IEnumerable<QsStatement> StripSnippetWrapping(IEnumerable<QsNamesp
         /// Builds the compilation for the Q# code or Q# snippet and referenced assemblies defined by the given options.
         /// Prints the data structures requested by the given options using the given logger.
         /// Returns a suitable error code if one of the compilation or generation steps fails.
-        /// Throws an ArgumentNullException if any of the given arguments is null.
         /// </summary>
         public static int Run(DiagnoseOptions options, ConsoleLogger logger)
         {
-            if (options == null)
-            {
-                throw new ArgumentNullException(nameof(options));
-            }
-            if (logger == null)
-            {
-                throw new ArgumentNullException(nameof(logger));
-            }
-
             if (!options.ParseAssemblyProperties(out var assemblyConstants))
             {
                 logger.Log(WarningCode.InvalidAssemblyProperties, Array.Empty<string>());

src/QsCompiler/CommandLineTool/Commands/Format.cs

@@ -71,14 +71,9 @@ public static string UpdateArrayLiterals(string fileContent)
         /// If the id of a file is consistent with the one assigned to a code snippet,
         /// strips the lines of code that correspond to the wrapping defined by WrapSnippet.
         /// Throws an ArgumentException if this is not possible because the given syntax tree is inconsistent with that wrapping.
-        /// Throws an ArgumentNullException if the given compilation is null.
         /// </summary>
         private static IEnumerable<string> GenerateQsCode(Compilation compilation, NonNullable<string> file, ILogger logger)
         {
-            if (compilation == null)
-            {
-                throw new ArgumentNullException(nameof(compilation));
-            }
             if (Options.IsCodeSnippet(file))
             {
                 var subtree = compilation.SyntaxTree.Values.Select(ns => FilterBySourceFile.Apply(ns, file)).Where(ns => ns.Elements.Any());
@@ -119,15 +114,9 @@ string FormatComments(IEnumerable<string> comments) =>
         /// logs the generated code using the given logger.
         /// Creates a file containing the generated code in the given output folder otherwise.
         /// Returns true if the generation succeeded, and false if an exception was thrown.
-        /// Throws an ArgumentNullException if the given compilation, the file uri or its absolute path are null.
         /// </summary>
         private static bool GenerateFormattedQsFile(Compilation compilation, NonNullable<string> fileName, string? outputFolder, ILogger logger)
         {
-            if (compilation == null)
-            {
-                throw new ArgumentNullException(nameof(compilation));
-            }
-
             var code = Enumerable.Empty<string>();
             try
             {
@@ -158,19 +147,9 @@ private static bool GenerateFormattedQsFile(Compilation compilation, NonNullable
         /// Generates formatted Q# code for each source file in the compilation.
         /// Returns a suitable error code if some of the source files or references could not be found or loaded, or if the Q# generation failed.
         /// Compilation errors are not reflected in the return code, but are logged using the given logger.
-        /// Throws an ArgumentNullException if any of the given arguments is null.
         /// </summary>
         public static int Run(FormatOptions options, ConsoleLogger logger)
         {
-            if (options == null)
-            {
-                throw new ArgumentNullException(nameof(options));
-            }
-            if (logger == null)
-            {
-                throw new ArgumentNullException(nameof(logger));
-            }
-
             ImmutableDictionary<Uri, string> LoadSources(SourceFileLoader loadFromDisk) =>
                 options.LoadSourcesOrSnippet(logger)(loadFromDisk)
                     .ToImmutableDictionary(entry => entry.Key, entry => UpdateArrayLiterals(entry.Value)); // manually replace array literals

src/QsCompiler/CommandLineTool/LoadContext.cs

@@ -39,7 +39,7 @@ public void RemoveFromPath(params string[] paths) =>
 
         private LoadContext(string parentAssembly)
         {
-            this.PathToParentAssembly = parentAssembly ?? throw new ArgumentNullException(nameof(parentAssembly));
+            this.PathToParentAssembly = parentAssembly;
             this.resolver = new AssemblyDependencyResolver(this.PathToParentAssembly);
             this.fallbackPaths = new HashSet<string>();
             this.Resolving += this.OnResolving;

src/QsCompiler/CommandLineTool/Logging.cs

@@ -40,14 +40,9 @@ public ConsoleLogger(
         /// <summary>
         /// Prints the given message to the Console.
         /// Errors and Warnings are printed to the error stream.
-        /// Throws an ArgumentNullException if the given message is null.
         /// </summary>
         private static void PrintToConsole(DiagnosticSeverity severity, string message)
         {
-            if (message == null)
-            {
-                throw new ArgumentNullException(nameof(message));
-            }
             var (stream, color) =
                 severity == DiagnosticSeverity.Error ? (Console.Error, ConsoleColor.Red) :
                 severity == DiagnosticSeverity.Warning ? (Console.Error, ConsoleColor.Yellow) :

src/QsCompiler/CompilationManager/AssemblyLoader.cs

@@ -31,19 +31,16 @@ public static class AssemblyLoader
         /// Returns false if some of the content could not be loaded successfully,
         /// possibly because the referenced assembly has been compiled with an older compiler version.
         /// If onDeserializationException is specified, invokes the given action on any exception thrown during deserialization.
-        /// Throws an ArgumentNullException if the given uri is null.
+        /// Throws an ArgumentException if the URI is not an absolute file URI.
         /// Throws a FileNotFoundException if no file with the given name exists.
         /// Throws the corresponding exceptions if the information cannot be extracted.
         /// </summary>
         public static bool LoadReferencedAssembly(Uri asm, out References.Headers headers, bool ignoreDllResources = false, Action<Exception>? onDeserializationException = null)
         {
-            if (asm == null)
+            var id = CompilationUnitManager.GetFileId(asm);
+            if (!File.Exists(asm.LocalPath))
             {
-                throw new ArgumentNullException(nameof(asm));
-            }
-            if (!CompilationUnitManager.TryGetFileId(asm, out var id) || !File.Exists(asm.LocalPath))
-            {
-                throw new FileNotFoundException($"The uri '{asm}' given to the assembly loader is invalid or the file does not exist.");
+                throw new FileNotFoundException($"The file '{asm.LocalPath}' given to the assembly loader does not exist.");
             }
 
             using var stream = File.OpenRead(asm.LocalPath);
@@ -65,18 +62,13 @@ public static bool LoadReferencedAssembly(Uri asm, out References.Headers header
         /// possibly because the referenced assembly has been compiled with an older compiler version.
         /// Catches any exception throw upon loading the compilation, and invokes onException with it if such an action has been specified.
         /// Sets the out parameter to null if an exception occurred during loading.
-        /// Throws an ArgumentNullException if the given uri is null.
         /// Throws a FileNotFoundException if no file with the given name exists.
         /// </summary>
         public static bool LoadReferencedAssembly(
             string asmPath,
             [NotNullWhen(true)] out QsCompilation? compilation,
             Action<Exception>? onException = null)
         {
-            if (asmPath == null)
-            {
-                throw new ArgumentNullException(nameof(asmPath));
-            }
             if (!File.Exists(asmPath))
             {
                 throw new FileNotFoundException($"The file '{asmPath}' does not exist.");
@@ -102,17 +94,12 @@ public static bool LoadReferencedAssembly(
         /// Given a stream containing the binary representation of compiled Q# code, returns the corresponding Q# compilation.
         /// Returns true if the compilation could be deserialized without throwing an exception, and false otherwise.
         /// If onDeserializationException is specified, invokes the given action on any exception thrown during deserialization.
-        /// Throws an ArgumentNullException if the given stream is null, but ignores exceptions thrown during deserialization.
         /// </summary>
         public static bool LoadSyntaxTree(
             Stream stream,
             [NotNullWhen(true)] out QsCompilation? compilation,
             Action<Exception>? onDeserializationException = null)
         {
-            if (stream == null)
-            {
-                throw new ArgumentNullException(nameof(stream));
-            }
             using var reader = new BsonDataReader(stream);
             (compilation, reader.ReadRootValueAsArray) = (null, false);
             try
@@ -141,18 +128,13 @@ private static ImmutableDictionary<string, ManifestResource> Resources(this Meta
         /// Given a reader for the byte stream of a dotnet dll, loads any Q# compilation included as a resource.
         /// Returns true as well as the loaded compilation if the given dll includes a suitable resource, and returns false otherwise.
         /// If onDeserializationException is specified, invokes the given action on any exception thrown during deserialization.
-        /// Throws an ArgumentNullException if any of the given readers is null.
         /// May throw an exception if the given binary file has been compiled with a different compiler version.
         /// </summary>
         private static bool FromResource(
             PEReader assemblyFile,
             [NotNullWhen(true)] out QsCompilation? compilation,
             Action<Exception>? onDeserializationException = null)
         {
-            if (assemblyFile == null)
-            {
-                throw new ArgumentNullException(nameof(assemblyFile));
-            }
             var metadataReader = assemblyFile.GetMetadataReader();
             compilation = null;
 
@@ -239,15 +221,10 @@ private static (string, string)? GetAttribute(MetadataReader metadataReader, Cus
         /// Given a reader for the byte stream of a dotnet dll, read its custom attributes and
         /// returns a tuple containing the name of the attribute and the constructor argument
         /// for all attributes defined in a Microsoft.Quantum* namespace.
-        /// Throws an ArgumentNullException if the given stream is null.
         /// Throws the corresponding exceptions if the information cannot be extracted.
         /// </summary>
         private static IEnumerable<(string, string)> LoadHeaderAttributes(PEReader assemblyFile)
         {
-            if (assemblyFile == null)
-            {
-                throw new ArgumentNullException(nameof(assemblyFile));
-            }
             var metadataReader = assemblyFile.GetMetadataReader();
             return metadataReader.GetAssemblyDefinition().GetCustomAttributes()
                 .Select(metadataReader.GetCustomAttribute)