Watcher error for emacs temp file

[bradyt]

Seems to be similar to this issue: #1134.

If I use pub run build_runner watch, and edit a file with Emacs,

[SEVERE] built_value_generator:built_value on lib/src/.#types.dart:

NoSuchMethodError: The getter 'element' was called on null.
Receiver: null
Tried calling: element
[SEVERE] Unhandled build failure!
FileSystemException: Cannot create file, path = '.dart_tool/build/098d3ee73e6cc294616d3a2e2c3c81ad/error_cache/cone_lib/0/lib/src/.' (OS Error: Is a directory, errno = 21)
[SEVERE] Failed after 7ms

Environment information:

$ dart --version
Dart VM version: 2.7.1 (Thu Jan 23 13:02:26 2020 +0100) on "macos_x64"

# pubspec.lock
...
  build_runner:
    dependency: "direct dev"
    description:
      name: build_runner
      url: "https://pub.dartlang.org"
    source: hosted
    version: "1.7.4"
...
  built_value:
    dependency: "direct main"
    description:
      name: built_value
      url: "https://pub.dartlang.org"
    source: hosted
    version: "7.0.9"
  built_value_generator:
    dependency: "direct dev"
    description:
      name: built_value_generator
      url: "https://pub.dartlang.org"
    source: hosted
    version: "7.0.9"
...

[jakemac53]

Looks like it is using a # as a prefix for the file names which confuses things unsurprisingly as that is a uri fragment. It seems to be getting stripped. This could be a problem with the watcher package or something in our code although we don't really work with uris, I would guess its something in watcher.

[jakemac53]

Hmm we do actually allow getting uris for AssetIds, which it looked like is partly where we had issues before.

Given that I don't think its even possible to create a sensible uri from this I am inclined to close this as not planned.

cc @natebosch

[jakemac53]

See here which I think is the actual culprit

build/build_runner_core/lib/src/logging/failure_reporter.dart

Line 116 in 4ab465c

p.fromUri(output.primaryInput.path));

Any idea why we are using p.fromUri for that @natebosch ?

[natebosch]

Any idea why we are using p.fromUri for that @natebosch ?

It's because the argument is the path part, which is always URI separator, not the OS separator.

The real problem is that we aren't escaping properly when we go from OS to URI style path somewhere I think. That path should really have the # escaped as %23

[natebosch]

@bradyt - can you try a git override for build_runner_core and see if it's working? Assuming it is I can publish.

We expect there may be build errors when you have files named .dart that aren't valid Dart files, but we hope that this resolves the stack trace.

[bradyt]

Ah, maybe there wasn't really anything broken. I tried the following as you suggested.

dependency_overrides:
  build_runner_core:
    version: '4.4.1-dev'
    git:
      url: https://github.com/dart-lang/build.git
      path: build_runner_core

Then I no longer see this:

FileSystemException: Cannot create file, path = '.dart_tool/build/098d3ee73e6cc294616d3a2e2c3c81ad/error_cache/cone_lib/0/lib/src/.' (OS Error: Is a directory, errno = 21)

But I still see the following:

[SEVERE] built_value_generator:built_value on lib/src/.#types.dart:

NoSuchMethodError: The getter 'element' was called on null.
Receiver: null
Tried calling: element

But nothing actually "breaks".

(Almost completely unrelated, but for context; if for example, I had an incorrect name in a Built class, then I would see logs like, Please make the following changes to use BuiltValue:, the .g.dart file would disappear, and that would break my usage of tools like ls lib/**/*.dart | entr -s 'pub run test'.)

[natebosch]

Treating these files as inputs to other build steps is harder to change - currently most builders assume that files ending in .dart are Dart files, and so adding non Dart files with that extension is likely going to cause problems.

I don't think we have a easy answer to that problem - there is a lot of stuff built on that assumption, and we don't want to hardcode support for a particular editor's behavior around "special" files.