implicit-downcasts in analysis_options doesn't work

[nex3]

If I have the following .analysis_options file:

analyzer:
  strong-mode:
  - implicit-downcasts: false
  - implicit-dynamic: false

and the following Dart file (taken from this example):

// test.dart

void main() {
  Object o = new Object();
  String s = o;  // Implicit downcast
  String s2 = s.substring(1);
}

and I run dartanalyzer test.dart, it only reports:

[hint] The value of the local variable 's2' is not used

The same is true if I run dartanalyzer --strong --no-implicit-casts test.dart. However, if I delete .analysis_options and run dartanalyzer --strong --no-implicit-casts test.dart, I get:

[error] A value of type 'Object' cannot be assigned to a variable of type 'String'
[hint] The value of the local variable 's2' is not used

I've tested this against Dart 1.20.1 and 1.19.0. I think the implicit-dynamic flag has the same issue, but I don't know of a simple file to test it on.

[jmesserly]

I believe you're looking for implicit-casts: false

[nex3]

That's not what the docs say...

[nex3]

Even if I change implicit-downcasts to implicit-casts in the analysis options file, the results are the same.

[jmesserly]

That's not what the docs say...

@Sfshaza - where would the best place to be for filing a documentation bug? The flag has always been called implicit-casts (https://github.com/dart-lang/dev_compiler/blob/master/doc/STATIC_SAFETY.md#disable-implicit-casts, https://github.com/dart-lang/sdk/blob/master/pkg/analyzer/lib/src/task/options.dart#L71)

@nex3 -- does it behave any better if you restart analysis server? We've seen bugs in the past where e.g. strong-mode will not be enabled correctly until a restart.

[nex3]

I'm not using the server, I'm just using the CLI.

[jmesserly]

Oh. I'm not familiar with under what conditions the CLI will use analysis_options. Does strong mode seem to be working at all?

[nex3]

I'm not sure. What's a good test case for that?

[jmesserly]

class C {
  int x() => 0;
}
class D extends C {
  Object x() => 'hi'; // strong mode: invalid override
}

[jmesserly]

@nex3 could this be the bug you are seeing: #26959

[nex3]

class C {
  int x() => 0;
}
class D extends C {
  Object x() => 'hi'; // strong mode: invalid override
}

If I analyze this with dartanalyzer and the .analysis_options file listed above, it emits no errors. Same if I replace implicit-downcasts with implicit-casts.

[jmesserly]

yeah, that means it's not running in strong mode. I believe you're seeing #26959 -- Analyzer CLI does not use analysis_options

[nex3]

I don't think that's it—I'm analyzing files, not directories, and if I write

analyzer:
  strong-mode: true

strong mode works fine.

[jmesserly]

this works for me:

analyzer:
  strong-mode:
    implicit-casts: false

[error] A value of type 'Object' can't be assigned to a variable of type 'String'. 

the problem is the leading "-", it's a YAML map not a list.
This was noted in the docs I wrote, so it looks like this is a problem with the live documentation.

Move this to https://github.com/dart-lang/site-www/issues?

[bwilkerson]

dartanalyzer, wrongly in my opinion, is sensitive to the current working directory. I think this sometimes causes problems with discovery of options files. I'm not sure that's what's happening in this case, though.

[jmesserly]

I believe this has been moved to dart-lang/site-www#161. thanks @nex3 !