In Dart, how do I get from the AST to Elements?
I generate the AST like this:
var ast = parseFile(path: "/home/user/myFile.dart", featureSet: FeatureSet.latestLanguageVersion());
I can access the declaration nodes, but I would like get to the Elements (e.g. LibraryElement, ClassElement, etc.).
How to do this?
The Dart Analyzer is built to work with a filesystem structure, and cannot build an element tree from a single file alone.
The analysis APIs to analyze a collection of files are described in this document.
On another note, the analyzer package also provides APIs to emulate a filesystem in-memory.
This means that library code in the form of a String can also be analyzed if need be, by emulating a file.
In order to analyse a single file, we can use these APIs alongside, if need be, an in-memory filesystem structure layered on top of the real filesystem, to allow the analyzer to access required SDK files in addition to the emulated file.
import 'package:analyzer/dart/analysis/analysis_context_collection.dart';
import 'package:analyzer/dart/analysis/results.dart';
import 'package:analyzer/file_system/overlay_file_system.dart';
import 'package:analyzer/file_system/physical_file_system.dart';
const filePath = '/path/to/myFile.dart';
final collection = AnalysisContextCollection(
includedPaths: const [filePath],
// If using an in-memory file, also provide a layered ResourceProvider:
resourceProvider: OverlayResourceProvider(PhysicalResourceProvider())
..setOverlay(
filePath,
content: libraryCode,
modificationStamp: 0,
),
);
final analysisSession = collection.contextFor(filePath).currentSession;
final libraryElement = await analysisSession
.getLibraryByUri('file://$filePath')
.then((libraryResult) => (libraryResult as LibraryElementResult).element);
Related
I'm trying to create a code generator that takes input a JSON file and generates multiple classes in multiple files.
And my question is, is it possible to create multiple files for one input using build from dart lang?
Yes it is possible. There are currently many tools in available on pub.dev that have code generation. For creating a simple custom code generator, check out the package code_builder provided by the core Dart team.
You can use dart_style as well to format the output of the code_builder results.
Here is a simple example of the package in use (from the package's example):
import 'package:code_builder/code_builder.dart';
import 'package:dart_style/dart_style.dart';
final _dartfmt = DartFormatter();
// The string of the generated code for AnimalClass
String animalClass() {
final animal = Class((b) => b
..name = 'Animal'
..extend = refer('Organism')
..methods.add(Method.returnsVoid((b) => b
..name = 'eat'
..body = refer('print').call([literalString('Yum!')]).code)));
return _dartfmt.format('${animal.accept(DartEmitter())}');
}
In this example you can use the dart:io API to create a File and write the output from animalClass() (from the example) to the file:
final animalDart = File('animal.dart');
// write the new file to the disk
animalDart.createSync();
// write the contents of the class to the file
animalDart.writeAsStringSync(animalClass());
You can use the File API to read a .json from the path, then use jsonDecode on the contents of the file to access the contents of the JSON config.
Is there a way to reflect specific library properties (like the library name) in Dart?
How do you get the library object reference?
First of all, not all Dart libraries have names. In fact, most don't. They used to, but the name isn't used for anything any more, so most library authors don't bother adding a name.
To do reflection on anything, including libraries, you need to use the dart:mirrors library, which does not exist on most platforms, including the web and Flutter.
If you are not running the stand-alone VM, you probably don't have dart:mirrors.
With dart:mirrors, you can get the program's libraries in various ways.
library my.library.name;
import "dart:mirrors";
final List<LibraryMirror> allLibraries =
[...currentMirrorSystem().libraries.values];
void main() {
// Recognize the library's mirror in *some* way.
var someLibrary = allLibraries.firstWhere((LibraryMirror library) =>
library.simpleName.toString().contains("name"));
// Find the library mirror by its name.
// Not great if you don't know the name and want to find it.
var currentLibrary = currentMirrorSystem().findLibrary(#my.library.name);
print(currentLibrary.simpleName);
// Find a declaration in the current library, and start from there.
var mainFunction = reflect(main) as ClosureMirror;
var alsoCurrentLibrary = mainFunction.function.owner as LibraryMirror;
print(alsoCurrentLibrary.simpleName);
}
What are you trying to do, which requires doing reflection?
My filename contains information that I need in my pipeline, for example the identifier for my data points is part of the filename and not a field in the data. e.g Every wind turbine generates a file turbine-loc-001-007.csv. e.g And I need the loc data within the pipeline.
Java (sdk 2.9.0):
Beams TextIO readers do not give access to the filename itself, for these use cases we need to make use of FileIO to match the files and gain access to the information stored in the file name. Unlike TextIO, the reading of the file needs to be taken care of by the user in transforms downstream of the FileIO read. The results of a FileIO read is a PCollection the ReadableFile class contains the file name as metadata which can be used along with the contents of the file.
FileIO does have a convenience method readFullyAsUTF8String() which will read the entire file into a String object, this will read the whole file into memory first. If memory is a concern you can work directly with the file with utility classes like FileSystems.
From: Document Link
PCollection<KV<String, String>> filesAndContents = p
.apply(FileIO.match().filepattern("hdfs://path/to/*.gz"))
// withCompression can be omitted - by default compression is detected from the filename.
.apply(FileIO.readMatches().withCompression(GZIP))
.apply(MapElements
// uses imports from TypeDescriptors
.into(KVs(strings(), strings()))
.via((ReadableFile f) -> KV.of(
f.getMetadata().resourceId().toString(), f.readFullyAsUTF8String())));
Python (sdk 2.9.0):
For 2.9.0 for python you will need to collect the list of URI from outside of the Dataflow pipeline and feed it in as a parameter to the pipeline. For example making use of FileSystems to read in the list of files via a Glob pattern and then passing that to a PCollection for processing.
Once fileio see PR https://github.com/apache/beam/pull/7791/ is available, the following code would also be an option for python.
import apache_beam as beam
from apache_beam.io import fileio
with beam.Pipeline() as p:
readable_files = (p
| fileio.MatchFiles(‘hdfs://path/to/*.txt’)
| fileio.ReadMatches()
| beam.Reshuffle())
files_and_contents = (readable_files
| beam.Map(lambda x: (x.metadata.path,
x.read_utf8()))
I have a use-case for a pub transformer that isn't very typical, so I'm wondering if it's possible. I'd like to individually gzip every css, html, and javascript file produced during pub build. I have two questions about this:
Is it possible to transform compiled javascript?
Is it possible to configure the order that the transformer is run? Obviously, the gzip transformer would need to be the last transformer run.
In case you're wondering why I want to do this, I'm serving my app via S3 which doesn't support on-the-fly gzipping. I figure pub transformers would be the most appropriate place to do this.
You can specify order by the line position of the transformer:
transformers:
- $dart2js
- YourGzipTransformer
The above specifies that you want the dart2js transformer to run before YourGzipTransformer, thereby giving YourGzipTransformer access to the Javascript files generated by dart2js. If you swapped the order, or did not specify the order of the dart2js transformer, YourGzipTransformer would run before it and not have access to the compiled Javascript.
If you didn't care what order some transformers ran in, you could specify that too:
transformers:
- [$dart2js, SomeOtherTransformer]
- YourGzipTransformer
You can read more about this in the Assets and Transformers article.
Here's a basic transformer that will generate a gzipped version of every CSS, HTML, and Javascript file:
import 'dart:io';
import 'package:barback/barback.dart';
class GzipTransformer extends Transformer {
final BarbackSettings _settings;
GzipTransformer.asPlugin(this._settings);
#override
Future apply(Transform transform) {
return transform.primaryInput.readAsString().then((content) {
var id = transform.primaryInput.id;
var gzipId = id.changeExtension(id.extension +".gzip");
var gzippedContent = GZIP.encode(content.codeUnits);
transform.addOutput(new Asset.fromBytes(gzipId, gzippedContent));
});
}
String get allowedExtensions => ".js .css .html";
}
I know you can use the library, import and even #import, but which is correct?
I have got two files, MainClass.dart and Library.Dart, and I want to add a reference to Library.dart in MainClass.dart. How can I do that?
Firstly let me just preface this by saying please do not use the hash symbol before import or library or anything else. This is an old syntax that is being deprecated. So we no longer want to use #import('...') The correct syntax is:
import 'some_file.dart';
That said, there are two different things we can do to access different dart source files within our current file. The first is to import the file. We use this such as in your case when you want to bring a different library into the current file (or more accurately current library).
Usually if your files are in the same directory, or a sub directory of the current one we would import them like this:
import 'lib/library.dart';
However If you are using the pub package layout you can also use some special short-cut references as well to import files (particularly from other packages you've imported). I highly suggest reading the documents on the pub site, as most applications and libraries are designed with this in mind. It also has suggestions on best naming conventions such as filenames in all lower case, and using underscore for spaces, and directory layouts.
The other important thing to know about bringing a dart file into another file, is that we can use the part and part of directives. This used to be called #source but was changed (with the removal of the hash sign) to reduce confusion. The part directive is used when we want to write a single library which spans multiple files. Say for instance you have an Awesome Library, which is starting to get a little large for a single file. We will create the main file of the library (not to be confused with the main method). This file will usually have the same name as the library itself.
// awesome_library.dart
library awesome_library;
import 'dart:math';
import '...';
// this injects all the content of secret_file.dart
// into this file right here almost as if it was
// here in the first place.
part 'src/secret_file.dart';
// The rest of our file here
// ...
The part directive basically takes everything from our src/secret_file.dart and inserts it into that part of the file. This allows us to split our huge Awesome Library into multiple smaller files that are easier to maintain. While not specifically required, it is helpful to use the part of directive in our secret_file.dart to help the editor know that it is "part of" the library.
// secret_file.dart
part of awesome_library;
// ... Rest of our secret_file code below.
Note that when using a part file like this, the part(s) (that is everything that is not the main file of the library) cannot import or use library declarations themselves. They import whatever is imported into the the main file, but they cannot add any additional imports.
For more information about library see this link.
Importing your own created libraries:
You will be importing the filename.dart and not the name of your library.
So if the name of your library is: myLib and it is saved in the file: someDartFile.dart you will have to
import 'someDartFile.dart';
If you have on Windows a library at: K:\SomeDir\someFile.dart you will need to write:
import '/K:/SomeDir/someFile.dart';
example:
import 'LibraryFile.dart'; //importing myLib
void main(){
//a class from myLib in the LibraryFile.dart file
var some = new SomeClassFromMyLibrary();
}
myLib in LibraryFile.dart:
library myLibrary;
import 'dart:math';
class SomeClassFromMyLibrary{
String _str = "this is some private String only to myLibrary";
String pubStr = "created instances of this class can access";
}
Here a full example.
//TestLib.dart
import 'LibFile.dart'; //SomeLibrary
void main() {
print("Hello, World!");
LibFile l = new LibFile();
print(l.publicString);//public
print(l.getPrivateString);//private
print(l.getMagicNumber); //42
}
//LibFile.dart
library SomeLibrary;
part 'LibFile2.dart';
class LibFile {
String _privateString = "private";
String publicString = "public";
String get getPrivateString => _privateString;
int get getMagicNumber => new LibFile2().number;
}
//LibFile2.dart
part of SomeLibrary;
class LibFile2 {
int number = 42;
}
Although i am answering very late, but the answer may help new developer.
Always use pubspec.yaml file in your dart package(application/library).
once you run pub get command it will add your local library in the dependencies list in .packages file.
Consider i have following project structure.
To refer to the content of greeting.dart in my main.dart file i should add the library as below
import 'package:my_project_name/greeting.dart'
Once imported we can use the content of greeting.dart file in our main.dart file.
Note: we have not used the actual path as you can see 'lib' directory is missing.
First make sure that's the name which you have mentioned in pubspec.yaml and the file you want to import are sharing the exact same name
example:
pubspec.yaml
name: flutter_wordpress_app
description: flutter wordpress app
...
....
// dirOne/dirTwo/greeting.dart
class FavArticleBloc {
// Your code goes here
}
import 'package:flutter_wordpress_app/dirOne/dirTwo/greeting.dart'
void main(){
var some = new FavArticleBloc();
}
But
in the main.dartyou don't need to specify
import 'package:flutter_wordpress_app
just do like below
import 'dirOne/dirTwo/greeting.dart