Crash: Null check operator used on a null value

[gs0-debiotech]

When running dartdoc on our application, we get the following failure:

$ dartdoc
Documenting app...
Discovering libraries...
Linking elements...
Precaching local docs for 151614 elements...
Initialized dartdoc with 366 libraries
[...snip...]
Generating docs for library data/dao/app_database_dao.dart from file:///builds/app/lib/data/dao/app_database_dao.dart...
dartdoc 8.3.3 (/root/.pub-cache/global_packages/dartdoc/bin/dartdoc.dart-3.7.0.snapshot) failed: Null check operator used on a null value
#0      Prefix.associatedLibrary (package:dartdoc/src/model/prefix.dart:30:54)
#1      Prefix.associatedLibrary (package:dartdoc/src/model/prefix.dart)
#2      Prefix.canonicalModelElement (package:dartdoc/src/model/prefix.dart:42:41)
#3      Prefix.href (package:dartdoc/src/model/prefix.dart:51:23)
#4      PackageGraph.allHrefs (package:dartdoc/src/model/package_graph.dart:599:33)
#5      new Validator (package:dartdoc/src/validator.dart:38:32)
#6      Dartdoc.generateDocsBase (package:dartdoc/src/dartdoc.dart:209:7)
<asynchronous suspension>
#7      Dartdoc.generateDocs (package:dartdoc/src/dartdoc.dart:241:24)
<asynchronous suspension>
#8      Dartdoc.executeGuarded.<anonymous closure> (package:dartdoc/src/dartdoc.dart:273:9)
<asynchronous suspension>

Link to prefix.dart:30 as of today.

I do not know whether it's linked to the last file read. In case it is, here is the code:

import 'dart:io';

import 'package:app/data/app_database.dart';
import 'package:drift/drift.dart';

part '../../generated/data/dao/app_database_dao.g.dart';

@DriftAccessor()
class AppDatabaseDao extends DatabaseAccessor<AppDatabase> with _$AppDatabaseDaoMixin {
  AppDatabaseDao(super.attachedDatabase);

  Future<void> exportInto(File file) async {
    await file.parent.create(recursive: true);
    await customStatement('VACUUM INTO ?', [file.path]);
  }
}

When checking since when it fails in our pipeline, I do not see anything special in the corresponding commit: only changes in the Dart code, few annotations used (@Freezed(toStringOverride), but nothing related to the tooling.

For context, it's running in a Linux gitlab worker, using the flutter:3.27.1 container from CirrusLabs up to flutter:3.29.1. The setup runs dart pub global activate dartdoc (which ends with Activated dartdoc 8.3.3, and the command is dartdoc.

I tried to replicate it locally (with Flutter 3.29.1 on macOS), and the doc generation works correctly, without a crash.

[srawlins]

That's funny that you have a prefix.dart as well. But the stack trace is referring to prefix.dart in dartdoc.

[srawlins]

My best guess is that on GitLab, the code-generation step has not been run yet. dartdoc is looking for an imported library and not finding it.

[gs0-debiotech]

That's funny that you have a prefix.dart as well. But the stack trace is referring to prefix.dart in dartdoc.

I'm not exactly sure what you mean. I do not have any "prefix" in my codebase, besides some prefixIcon (or the word "prefix" in the doc-comments).

Thank you for having a look on my issue! Is there an easy way for me to test the fix in your MR?

[srawlins]

Oh I thought the code you showed, with @DriftAccessor(), was from a prefix.dart file. I misread, and didn't click the link.

[srawlins]

Is there an easy way for me to test the fix in your MR?

You can run dartdoc from the git branch, or from the main branch when it lands. Maybe something like this.

[gs0-debiotech]

Is it OK if I continue the discussion here, despite the closed issue?

I've tried the commit f41bd3a from main:

$ dart pub global activate --source git https://github.com/dart-lang/dartdoc/ --git-ref f41bd3ab4bd34c048f2c803174f16bc128acadaa
Resolving dependencies...
Downloading packages...
+ _fe_analyzer_shared 80.0.0
+ analyzer 7.3.0
+ args 2.7.0
+ async 2.13.0
+ collection 1.19.1
+ convert 3.1.2
+ crypto 3.0.6
+ csslib 1.0.2
+ dartdoc 8.3.3 from git https://github.com/dart-lang/dartdoc/ at f41bd3
+ file 7.0.1
+ glob 2.1.3
+ html 0.15.5
+ logging 1.3.0
+ markdown 7.3.0
+ meta 1.16.0
+ package_config 2.2.0
+ path 1.9.1
+ pub_semver 2.2.0
+ source_span 1.10.1
+ string_scanner 1.4.1
+ term_glyph 1.2.2
+ typed_data 1.4.0
+ watcher 1.1.1
+ yaml 3.1.3
Building package executables...
Built dartdoc:dartdoc.
Installed executable dartdoc.
Activated dartdoc 8.3.3 from Git repository "https://github.com/dart-lang/dartdoc/".
$ dartdoc
Documenting app...
Discovering libraries...
Linking elements...
Precaching local docs for 152133 elements...
Initialized dartdoc with 378 libraries
[...snip...]
Generating docs for library data/dao/app_database_dao.dart from file:///builds/app/lib/data/dao/app_database_dao.dart...
dartdoc 8.3.3 (/root/.pub-cache/global_packages/dartdoc/bin/dartdoc.dart-3.7.0.snapshot) failed: Bad state: Unexpected null LibraryElement2 for imported library at Instance of 'DirectiveUriWithRelativeUriImpl'
#0      Prefix._importedLibraryElement (package:dartdoc/src/model/prefix.dart:39:7)
#1      Prefix.associatedLibrary (package:dartdoc/src/model/prefix.dart:29:26)
#2      Prefix.associatedLibrary (package:dartdoc/src/model/prefix.dart)
#3      Prefix.canonicalModelElement (package:dartdoc/src/model/prefix.dart:47:41)
#4      Prefix.href (package:dartdoc/src/model/prefix.dart:56:23)
#5      PackageGraph.allHrefs (package:dartdoc/src/model/package_graph.dart:599:33)
#6      new Validator (package:dartdoc/src/validator.dart:38:32)
#7      Dartdoc.generateDocsBase (package:dartdoc/src/dartdoc.dart:209:7)
<asynchronous suspension>
#8      Dartdoc.generateDocs (package:dartdoc/src/dartdoc.dart:241:24)
<asynchronous suspension>
#9      Dartdoc.executeGuarded.<anonymous closure> (package:dartdoc/src/dartdoc.dart:273:9)
<asynchronous suspension>

Unfortunately, the doc still cannot be generated.

[srawlins]

The change I made will not allow any new docs to be generated. It's just debugging info.

My best guess is that on GitLab, the code-generation step has not been run yet. dartdoc is looking for an imported library and not finding it.

[gs0-debiotech]

Thanks you. I've noticed that the problem appears locally when running flutter clean before running dartdoc. A simple dart pub get fixed the generation problem (no need to build).