Crash handling anonymous functions as keys to a Map with inferred types

[bergwerf]

dartdoc version: 0.17.1+1

Generation failed: NoSuchMethodError: The getter 'length' was called on null.
Receiver: null
Tried calling: length
dart:convert                                                                          HtmlEscape.convert
package:dartdoc/src/model.dart 3416                                                   ModelElement._calculateLinkedName
package:dartdoc/src/model.dart 3097                                                   ModelElement.linkedName
package:dartdoc/src/element_type.dart 127                                             ParameterizedElementType.linkedName
package:dartdoc/src/element_type.dart 304                                             CallableAnonymousElementType.linkedName
package:dartdoc/src/element_type.dart 133                                             ParameterizedElementType.linkedName.<fn>
dart:core                                                                             StringBuffer.writeAll
package:dartdoc/src/element_type.dart 133                                             ParameterizedElementType.linkedName
package:dartdoc/src/element_type.dart 224                                             DefinedElementType.createLinkedReturnTypeName
package:dartdoc/src/model.dart 278                                                    Accessor.linkedReturnType
package:dartdoc/src/model.dart 1646                                                   ModelElement&GetterSetterCombo.linkedReturnType
dart:mirrors                                                                          _LocalInstanceMirror.getField
package:mustache4dart/src/mirrors.dart 111                                            _MethodMirrorField.val
package:mustache4dart/mustache_context.dart 122                                       _MustacheContext._getMustacheContext
package:mustache4dart/mustache_context.dart 118                                       _MustacheContext._getContextForKey
package:mustache4dart/mustache_context.dart 82                                        _MustacheContext._getInThisOrParent
package:mustache4dart/mustache_context.dart 78                                        _MustacheContext.field
package:mustache4dart/src/tokens.dart 169                                             _ExpressionToken.apply
package:mustache4dart/src/tokens.dart 40                                              Token.call
package:mustache4dart/src/tmpl.dart 101                                               _Template._write
package:mustache4dart/src/tmpl.dart 76                                                _Template.call
package:mustache4dart/src/mustache.dart 11                                            render
package:mustache4dart/src/tokens.dart 211                                             _PartialToken.apply
package:mustache4dart/src/tokens.dart 286                                             _StartSectionToken.apply.<fn>.<fn>
package:mustache4dart/src/tokens.dart 309                                             _StartSectionToken.forEachUntilEndSection
package:mustache4dart/src/tokens.dart 286                                             _StartSectionToken.apply.<fn>
dart:core                                                                             Iterable.forEach
package:mustache4dart/src/tokens.dart 285                                             _StartSectionToken.apply
package:mustache4dart/src/tokens.dart 299                                             _StartSectionToken.apply.<fn>
package:mustache4dart/src/tokens.dart 309                                             _StartSectionToken.forEachUntilEndSection
package:mustache4dart/src/tokens.dart 299                                             _StartSectionToken.apply
package:mustache4dart/src/tokens.dart 40                                              Token.call
package:mustache4dart/src/tmpl.dart 101                                               _Template._write
package:mustache4dart/src/tmpl.dart 76                                                _Template.call
package:dartdoc/src/html/html_generator_instance.dart 283                             HtmlGeneratorInstance._build
package:dartdoc/src/html/html_generator_instance.dart 180                             HtmlGeneratorInstance.generateLibrary
package:dartdoc/src/html/html_generator_instance.dart 93                              HtmlGeneratorInstance._generateDocs
package:dartdoc/src/html/html_generator_instance.dart 36                              HtmlGeneratorInstance.generate
===== asynchronous gap ===========================
dart:async                                                                            _Completer.completeError
package:dartdoc/src/html/html_generator_instance.dart                                 HtmlGeneratorInstance.generate
===== asynchronous gap ===========================
dart:async                                                                            new Future.microtask
package:dartdoc/src/html/html_generator_instance.dart 34                              HtmlGeneratorInstance.generate
package:dartdoc/src/html/html_generator.dart 106                                      HtmlGenerator.generate
===== asynchronous gap ===========================
dart:async                                                                            new Future.microtask
package:dartdoc/src/html/html_generator.dart 72                                       HtmlGenerator.generate
package:dartdoc/dartdoc.dart 171                                                      DartDoc.generateDocs
===== asynchronous gap ===========================
dart:async                                                                            _asyncThenWrapperHelper
package:dartdoc/dartdoc.dart 157                                                      DartDoc.generateDocs
/tmp/tmpvgnPvD/dart-2.0.0-dev.39.0/dart/third_party/pkg/dartdoc/bin/dartdoc.dart 274  main.<fn>.<fn>
===== asynchronous gap ===========================
dart:async                                                                            new Future.microtask
/tmp/tmpvgnPvD/dart-2.0.0-dev.39.0/dart/third_party/pkg/dartdoc/bin/dartdoc.dart 273  main.<fn>.<fn>
dart:async                                                                            runZoned
/tmp/tmpvgnPvD/dart-2.0.0-dev.39.0/dart/third_party/pkg/dartdoc/bin/dartdoc.dart 273  main.<fn>
===== asynchronous gap ===========================
dart:async                                                                            new Future.microtask
/tmp/tmpvgnPvD/dart-2.0.0-dev.39.0/dart/third_party/pkg/dartdoc/bin/dartdoc.dart 272  main.<fn>
package:stack_trace                                                                   Chain.capture
/tmp/tmpvgnPvD/dart-2.0.0-dev.39.0/dart/third_party/pkg/dartdoc/bin/dartdoc.dart 272  main

[jcollins-g]

Thanks for the report, @bergwerf! Can you share the command line you used and package (if public) you were attempting to document?

[bergwerf]

I ran dartdoc in the root of my project. The code is not public, and I did not seem to be able to narrow down the problem yesterday. There is a bit of extra context information:

Generating documentation for 'expr' into /home/herman/repos/qedb/expr/doc/api/
parsing lib/testenv.dart...
parsing lib/expr.dart...
parsing /usr/lib/dart/lib/_internal/js_runtime/lib/interceptors.dart...
Initialized dartdoc with 3 libraries in 2.3 seconds
documenting expr
Generating docs for library expr from package:expr/expr.dart...
  warning: unresolved doc reference [Set.identity]
    from expr.Expr.contains: (file:///home/herman/.pub-cache/hosted/pub.dartlang.org/quiver-0.28.1/lib/src/collection/delegates/iterable.dart:39:8)
    in documentation inherited from dart-core.Iterable.contains: (file:///usr/lib/dart/lib/core/iterable.dart:280:8)
Generating docs for library expr.test.testenv from package:expr/testenv.dart...
  warning: expr.test.testenv has no library level documentation comments, from expr.test.testenv: (file:///home/herman/repos/qedb/expr/lib/testenv.dart:5:9)
  warning: no canonical library found for expr.test.testenv.null, not linking, from expr.test.testenv.null: (file:///home/herman/repos/qedb/expr/lib/testenv.dart:0:0)

Generation failed: NoSuchMethodError: The getter 'length' was called on null.
Receiver: null
Tried calling: length
dart:convert                                                                          HtmlEscape.convert
package:dartdoc/src/model.dart 3416                                                   ModelElement._calculateLinkedName
package:dartdoc/src/model.dart 3097                                                   ModelElement.linkedName
package:dartdoc/src/element_type.dart 127                                             ParameterizedElementType.linkedName
package:dartdoc/src/element_type.dart 304                                             CallableAnonymousElementType.linkedName
package:dartdoc/src/element_type.dart 133                                             ParameterizedElementType.linkedName.<fn>
dart:core                                                                             StringBuffer.writeAll
package:dartdoc/src/element_type.dart 133                                             ParameterizedElementType.linkedName
package:dartdoc/src/element_type.dart 224                                             DefinedElementType.createLinkedReturnTypeName
package:dartdoc/src/model.dart 278                                                    Accessor.linkedReturnType
package:dartdoc/src/model.dart 1646                                                   ModelElement&GetterSetterCombo.linkedReturnType
dart:mirrors                                                                          _LocalInstanceMirror.getField
package:mustache4dart/src/mirrors.dart 111                                            _MethodMirrorField.val
package:mustache4dart/mustache_context.dart 122                                       _MustacheContext._getMustacheContext
package:mustache4dart/mustache_context.dart 118                                       _MustacheContext._getContextForKey
package:mustache4dart/mustache_context.dart 82                                        _MustacheContext._getInThisOrParent
package:mustache4dart/mustache_context.dart 78                                        _MustacheContext.field
package:mustache4dart/src/tokens.dart 169                                             _ExpressionToken.apply
package:mustache4dart/src/tokens.dart 40                                              Token.call
package:mustache4dart/src/tmpl.dart 101                                               _Template._write
package:mustache4dart/src/tmpl.dart 76                                                _Template.call
package:mustache4dart/src/mustache.dart 11                                            render
package:mustache4dart/src/tokens.dart 211                                             _PartialToken.apply
package:mustache4dart/src/tokens.dart 286                                             _StartSectionToken.apply.<fn>.<fn>
package:mustache4dart/src/tokens.dart 309                                             _StartSectionToken.forEachUntilEndSection
package:mustache4dart/src/tokens.dart 286                                             _StartSectionToken.apply.<fn>
dart:core                                                                             Iterable.forEach
package:mustache4dart/src/tokens.dart 285                                             _StartSectionToken.apply
package:mustache4dart/src/tokens.dart 299                                             _StartSectionToken.apply.<fn>
package:mustache4dart/src/tokens.dart 309                                             _StartSectionToken.forEachUntilEndSection
package:mustache4dart/src/tokens.dart 299                                             _StartSectionToken.apply
package:mustache4dart/src/tokens.dart 40                                              Token.call
package:mustache4dart/src/tmpl.dart 101                                               _Template._write
package:mustache4dart/src/tmpl.dart 76                                                _Template.call
package:dartdoc/src/html/html_generator_instance.dart 283                             HtmlGeneratorInstance._build
package:dartdoc/src/html/html_generator_instance.dart 180                             HtmlGeneratorInstance.generateLibrary
package:dartdoc/src/html/html_generator_instance.dart 93                              HtmlGeneratorInstance._generateDocs
package:dartdoc/src/html/html_generator_instance.dart 36                              HtmlGeneratorInstance.generate
===== asynchronous gap ===========================
dart:async                                                                            _Completer.completeError
package:dartdoc/src/html/html_generator_instance.dart                                 HtmlGeneratorInstance.generate
===== asynchronous gap ===========================
dart:async                                                                            new Future.microtask
package:dartdoc/src/html/html_generator_instance.dart 34                              HtmlGeneratorInstance.generate
package:dartdoc/src/html/html_generator.dart 106                                      HtmlGenerator.generate
===== asynchronous gap ===========================
dart:async                                                                            new Future.microtask
package:dartdoc/src/html/html_generator.dart 72                                       HtmlGenerator.generate
package:dartdoc/dartdoc.dart 171                                                      DartDoc.generateDocs
===== asynchronous gap ===========================
dart:async                                                                            _asyncThenWrapperHelper
package:dartdoc/dartdoc.dart 157                                                      DartDoc.generateDocs
/tmp/tmpvgnPvD/dart-2.0.0-dev.39.0/dart/third_party/pkg/dartdoc/bin/dartdoc.dart 274  main.<fn>.<fn>
===== asynchronous gap ===========================
dart:async                                                                            new Future.microtask
/tmp/tmpvgnPvD/dart-2.0.0-dev.39.0/dart/third_party/pkg/dartdoc/bin/dartdoc.dart 273  main.<fn>.<fn>
dart:async                                                                            runZoned
/tmp/tmpvgnPvD/dart-2.0.0-dev.39.0/dart/third_party/pkg/dartdoc/bin/dartdoc.dart 273  main.<fn>
===== asynchronous gap ===========================
dart:async                                                                            new Future.microtask
/tmp/tmpvgnPvD/dart-2.0.0-dev.39.0/dart/third_party/pkg/dartdoc/bin/dartdoc.dart 272  main.<fn>
package:stack_trace                                                                   Chain.capture
/tmp/tmpvgnPvD/dart-2.0.0-dev.39.0/dart/third_party/pkg/dartdoc/bin/dartdoc.dart 272  main

I could sent you a zip with the code (its a side project, and not super sensitive).

[jcollins-g]

The stack trace suggests this is related to a top-level variable and/or accessor exposed in package:expr/testenv.dart (either declared in or reexported there). This variable has a complex type including one or more type parameters, one of which is using the new generic function type syntax as a parameter, possibly. I'll poke around a bit and see if I can create a similar situation to reproduce this crash, but let me know if this information helps you narrow it down on your side. The zip could also be quite helpful if you can send that.

[jcollins-g]

I have found some other bugs for sure in this area. It might be that I'll accidentally fix yours as well.

[jcollins-g]

example:

ATypeTakingClass<String Function(int)> get complicatedReturn => null;

Generation failed: NoSuchMethodError: The getter 'packageGraph' was called on null.
Receiver: null
Tried calling: packageGraph
dart:core                                                     Object.noSuchMethod
package:dartdoc/src/model.dart 2544:17                        new ModelElement.from
package:dartdoc/src/model.dart 2508:16                        new ModelElement.fromElement
package:dartdoc/src/element_type.dart 28:15                   new ElementType.from
package:dartdoc/src/element_type.dart 231:27                  DefinedElementType.typeArguments.<fn>
dart:_internal                                                ListIterable.toList
package:dartdoc/src/element_type.dart 232:12                  DefinedElementType.typeArguments
package:dartdoc/src/element_type.dart 129:12                  ParameterizedElementType.linkedName
package:dartdoc/src/element_type.dart 224:53                  DefinedElementType.createLinkedReturnTypeName
package:dartdoc/src/model.dart 278:22                         Accessor.linkedReturnType
package:dartdoc/src/model.dart 1646:21                        ModelElement&GetterSetterCombo.linkedReturnType
dart:mirrors                                                  _LocalInstanceMirror.getField
package:mustache4dart/src/mirrors.dart 111:35                 _MethodMirrorField.val
package:mustache4dart/mustache_context.dart 122:45            _MustacheContext._getMustacheContext
package:mustache4dart/mustache_context.dart 118:12            _MustacheContext._getContextForKey
package:mustache4dart/mustache_context.dart 82:18             _MustacheContext._getInThisOrParent
package:mustache4dart/mustache_context.dart 78:12             _MustacheContext.field
package:mustache4dart/src/tokens.dart 169:21                  _ExpressionToken.apply
package:mustache4dart/src/tokens.dart 40:18                   Token.call
package:mustache4dart/src/tmpl.dart 101:20                    _Template._write
package:mustache4dart/src/tmpl.dart 76:5                      _Template.call
package:mustache4dart/src/mustache.dart 11:64                 render
package:mustache4dart/src/tokens.dart 211:16                  _PartialToken.apply
package:mustache4dart/src/tokens.dart 286:57                  _StartSectionToken.apply.<fn>.<fn>
package:mustache4dart/src/tokens.dart 309:8                   _StartSectionToken.forEachUntilEndSection
package:mustache4dart/src/tokens.dart 286:9                   _StartSectionToken.apply.<fn>
dart:core                                                     Iterable.forEach
package:mustache4dart/src/tokens.dart 285:27                  _StartSectionToken.apply
package:mustache4dart/src/tokens.dart 299:53                  _StartSectionToken.apply.<fn>
package:mustache4dart/src/tokens.dart 309:8                   _StartSectionToken.forEachUntilEndSection
package:mustache4dart/src/tokens.dart 299:5                   _StartSectionToken.apply
package:mustache4dart/src/tokens.dart 40:18                   Token.call
package:mustache4dart/src/tmpl.dart 101:20                    _Template._write
package:mustache4dart/src/tmpl.dart 76:5                      _Template.call
package:dartdoc/src/html/html_generator_instance.dart 283:30  HtmlGeneratorInstance._build
package:dartdoc/src/html/html_generator_instance.dart 180:5   HtmlGeneratorInstance.generateLibrary
package:dartdoc/src/html/html_generator_instance.dart 93:7    HtmlGeneratorInstance._generateDocs
package:dartdoc/src/html/html_generator_instance.dart 36:7    HtmlGeneratorInstance.generate

[jcollins-g]

@bergwerf If you have time to run dartdoc in checked mode (pub global run -c dartdoc:dartdoc) that will cause dartdoc to possibly throw earlier, at a point which might shed more light on the problem.

[bergwerf]

I was able to narrow it down to this global scope variable (simply by commenting parts of my code to see if the error was still produced):

final computations = {
  1: (List<num> a) => a[0] + a[1],
  2: (List<num> a) => a[0] - a[1],
  3: (List<num> a) => a[0] * a[1],
  4: (List<num> a) => -a[0]
};

[bergwerf]

I now got rid of the error by adding a typedef for this map: typedef num EvalArgs(List<num> args);, and adding a type after final.

[jcollins-g]

Ah, yes, that's tricky but your fix shouldn't be necessary. If it's OK, I'll use the exact example in my tests to make sure we've got this right in the future.

[bergwerf]

Yes, I am ok with you using this example.