C#: Only serialize the location if it is present

Author: henrymercer

csharp/extractor/Semmle.Util/ToolStatusPage.cs

@@ -151,7 +151,7 @@ public TspLocation(string? file = null, int? startLine = null, int? startColumn
         /// </summary>
         public bool Internal { get; }
         public TspVisibility Visibility { get; }
-        public TspLocation Location { get; }
+        public TspLocation? Location { get; }
         /// <summary>
         /// Structured metadata about the diagnostic message.
         /// </summary>
@@ -173,7 +173,7 @@ public DiagnosticMessage(
             this.Attributes = new Dictionary<string, object>();
             this.Severity = severity;
             this.Visibility = visibility ?? TspVisibility.All;
-            this.Location = location ?? new TspLocation();
+            this.Location = location;
             this.Internal = intrnl ?? false;
             this.MarkdownMessage = markdownMessage;
             this.PlaintextMessage = plaintextMessage;

csharp/ql/integration-tests/all-platforms/diag_dotnet_incompatible/diagnostics.expected

@@ -2,7 +2,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "CodeQL found some projects which cannot be built with .NET Core:\n\n- `test.csproj`",
   "severity": "warning",
   "source": {
@@ -20,7 +19,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "CodeQL was unable to build the following projects using MSBuild:\n\n- `test.csproj`\n\nSet up a [manual build command](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-the-codeql-workflow-for-compiled-languages).",
   "severity": "error",
   "source": {

csharp/ql/integration-tests/all-platforms/diag_missing_project_files/diagnostics.expected

@@ -2,7 +2,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "CodeQL was unable to build the following projects using MSBuild:\n\n- `test.sln`\n\nSet up a [manual build command](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-the-codeql-workflow-for-compiled-languages).",
   "severity": "error",
   "source": {
@@ -20,7 +19,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "Some project files were not found when CodeQL built your project:\n\n- `Example.csproj`\n- `Example.Test.csproj`\n\nThis may lead to subsequent failures. You can check for common causes for missing project files:\n\n- Ensure that the project is built using the [intended operating system](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idruns-on) and that filenames on case-sensitive platforms are correctly specified.\n- If your repository uses Git submodules, ensure that those are [checked out](https://github.com/actions/checkout#usage) before the CodeQL action is run.\n- If you auto-generate some project files as part of your build process, ensure that these are generated before the CodeQL action is run.",
   "severity": "error",
   "source": {

csharp/ql/integration-tests/all-platforms/diag_missing_xamarin_sdk/diagnostics.expected

@@ -2,7 +2,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "CodeQL was unable to build the following projects using .NET Core:\n\n- `test.csproj`\n\nSet up a [manual build command](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-the-codeql-workflow-for-compiled-languages).",
   "severity": "error",
   "source": {
@@ -20,7 +19,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "CodeQL was unable to build the following projects using MSBuild:\n\n- `test.csproj`\n\nSet up a [manual build command](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-the-codeql-workflow-for-compiled-languages).",
   "severity": "error",
   "source": {
@@ -38,7 +36,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "[Configure your workflow](https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-xamarin-applications) for this SDK before running CodeQL.",
   "severity": "error",
   "source": {

csharp/ql/integration-tests/posix-only/diag_autobuild_script/diagnostics.expected

@@ -2,7 +2,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "CodeQL attempted to build your project using a script located at `build.sh`, which failed. Set up a [manual build command](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-the-codeql-workflow-for-compiled-languages).",
   "severity": "error",
   "source": {
@@ -20,7 +19,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "CodeQL could not find any project or solution files in your repository. Set up a [manual build command](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-the-codeql-workflow-for-compiled-languages).",
   "severity": "error",
   "source": {

csharp/ql/integration-tests/posix-only/diag_multiple_scripts/diagnostics.expected

@@ -2,7 +2,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "CodeQL could not find any project or solution files in your repository. Set up a [manual build command](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-the-codeql-workflow-for-compiled-languages).",
   "severity": "error",
   "source": {
@@ -20,7 +19,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "CodeQL found multiple potential build scripts for your project and attempted to run `build.sh`, which failed. This may not be the right build script for your project. Set up a [manual build command](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-the-codeql-workflow-for-compiled-languages).",
   "severity": "error",
   "source": {

csharp/ql/integration-tests/windows-only/diag_autobuild_script/diagnostics.expected

@@ -2,7 +2,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "CodeQL attempted to build your project using a script located at `build.bat`, which failed. Set up a [manual build command](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-the-codeql-workflow-for-compiled-languages).",
   "severity": "error",
   "source": {
@@ -20,7 +19,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "CodeQL could not find any project or solution files in your repository. Set up a [manual build command](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-the-codeql-workflow-for-compiled-languages).",
   "severity": "error",
   "source": {

csharp/ql/integration-tests/windows-only/diag_multiple_scripts/diagnostics.expected

@@ -2,7 +2,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "CodeQL could not find any project or solution files in your repository. Set up a [manual build command](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-the-codeql-workflow-for-compiled-languages).",
   "severity": "error",
   "source": {
@@ -20,7 +19,6 @@
   "attributes": {},
   "helpLinks": [],
   "internal": false,
-  "location": {},
   "markdownMessage": "CodeQL found multiple potential build scripts for your project and attempted to run `build.bat`, which failed. This may not be the right build script for your project. Set up a [manual build command](https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-the-codeql-workflow-for-compiled-languages).",
   "severity": "error",
   "source": {