[Bug] NullPointerException during content generation

[thejonan]

Describe the bug
A NullPointerException during tool execution, after updating to version 2.75.3 (previous version used is 2.66.2 and the error did not show up).

Here's the stack trace:

NullReferenceException: Object reference not set to an instance of an object.
  at ConfigFilterRuleItem get_Rule() in ConfigFilterRuleItemUnion.cs:57
  at bool CanVisitCore(IEnumerable<ConfigFilterRuleItemUnion> ruleItems, SymbolFilterData symbol) in ConfigFilterRule.cs:
     30
  at bool CanVisitApi(SymbolFilterData symbol) in ConfigFilterRule.cs:20
  at bool <IncludeApi>g__IncludeApiDefault|1(ISymbol symbol) in SymbolFilter.cs:46
  at bool <IncludeApi>b__0(ISymbol _) in SymbolFilter.cs:40
  at TValue GetOrAdd(TKey key, Func<TKey, TValue> valueFactory)
  at bool IncludeApi(ISymbol symbol) in SymbolFilter.cs:31
  at IEnumerable<INamespaceSymbol> GetAllNamespaces(IAssemblySymbol assembly, SymbolFilter filter) in SymbolHelper.cs:106
  at IEnumerable<TResult> SelectManyIterator<TSource,TCollection,TResult>(IEnumerable<TSource> source, Func<TSource,
     IEnumerable<TCollection>> collectionSelector, Func<TSource, TCollection, TResult> resultSelector)
  at bool MoveNext()
  at IEnumerable<TResult> SelectManyIterator<TSource,TCollection,TResult>(IEnumerable<TSource> source, Func<TSource,
     IEnumerable<TCollection>> collectionSelector, Func<TSource, TCollection, TResult> resultSelector)
  at bool MoveNext()
  at void AddRange(IEnumerable<T> items)
  at bool ReserveOrAdd(IEnumerable<T> items)
  at TResult[[]] ToArray()
  at void CreateManagedReference((ValueTuple<IAssemblySymbol, Compilation> symbol) assemblies, ExtractMetadataConfig
     config, DotnetApiOptions options) in DotnetApiCatalog.ManagedReference.cs:19
  at async Task <Exec>g__Build|5_0(ExtractMetadataConfig config, DotnetApiOptions options) in DotnetApiCatalog.cs:123
  at async Task Exec(MetadataJsonConfig config, DotnetApiOptions options, string configDirectory, string outputDirectory)
     in DotnetApiCatalog.cs:75
  at void <Execute>b__0() in DefaultCommand.cs:45
  at int Run(LogOptions options, Action run) in CommandHelper.cs:48
  at int Execute(CommandContext context, Options options) in DefaultCommand.cs:31
  at Task<int> Execute(CommandContext context, CommandSettings settings) in CommandOfT.cs:40
  at Task<int> Execute(CommandTree leaf, CommandTree tree, CommandContext context, ITypeResolver resolver, IConfiguration
     configuration) in CommandExecutor.cs:144
  at async Task<int> Execute(IConfiguration configuration, IEnumerable<string> args) in CommandExecutor.cs:83
  at async Task<int> RunAsync(IEnumerable<string> args) in CommandApp.cs:84

Here is a (modified) configuration file:

{
  "metadata": [{
    "src": [{
      "files": ["CoreProject.csproj"],
      "src": "../"
    }, {
      "files": ["DependentProject1.csproj", "DependentProject2.csproj"],
      "src": "../"
    }],
    "dest": "api",
    "filter": "docfx-filter-config.yml",
    "disableGitFeatures": true,
    "disableDefaultFilter": false
  }],
  "build": {
    "content": [{
      "files": ["**.yml", "**.md"],
      "exclude": "docfx-filter-config.yml"
    }],
    "resource": [{
      "files": ["images/**"]
    }],
    "overwrite": [{
      "files": ["**.md"],
      "exclude": [
        "obj/**",
        "bin/**",
        "_site/**"
      ]
    }],
    "dest": "../public",
    "_globalMetadata": {
      "_appTitle": "Custom API",
      "_enableSearch": true
    },
    "globalMetadataFiles": [],
    "fileMetadataFiles": [],
    "template": ["default"],
    "postProcessors": [],
    "noLangKeyword": false,
    "keepFileLink": false,
    "cleanupCacheHistory": true,
    "disableGitFeatures": true,
    "force": true
  }
}

And here is the filter file referred:

apiRules:
- include:
  uidRegex: ^MyCompany\.MyNamespace\.Core.+
- exclude:
  uidRegex: _[^.]+$

The command used to invoke the generation is:

./bin/docfx Docs/docfx.json --serve

Context (please complete the following information):

• macOS (Sonoma 14.3.1)
• Linux (mcr.microsoft.com/dotnet/sdk:7.0 docker image).
• Docfx version: 2.75.3

[filzrev]

uidRegex must be defined with indentation as follows

apiRules:
- include:
    uidRegex: ^MyCompany\.MyNamespace\.Core.+
- exclude:
    uidRegex: _[^.]+$

Error is occurred at following lines

docfx/src/Docfx.Dotnet/Filters/ConfigFilterRuleItemUnion.cs

Lines 56 to 57 in ca358a5

	// If kind is not specified for exclude. Set `ExtendedSymbolKind.Type` as default kind.
	Exclude.Kind ??= ExtendedSymbolKind.Type | ExtendedSymbolKind.Member;

that lines are added by #9666.
I'll create PR to fix problems later.

For prior than docfx 2.75.2.
uidRegex is simply ignored on YAML deserialization. and include/exclude rules are ignored. if defined without indents.

[thejonan]

Thanks for the quick response!

So, now uidRegex for both include and exclude will be taken into account?

[filzrev]

now uidRegex for both include and exclude will be taken into account?

As far as I've tested with 2.75.3 with modified filterConfig.
Specified exclude rule works as expected (types that uid contains _ is not included at API metadata).

For specified include rule.
It don't affect filtering behaviors because public types are already included by default.

[thejonan]

Ok. Thanks!