# dart2js_info **Repository Path**: mirrors_chromium_googlesource/dart2js_info ## Basic Information - **Project Name**: dart2js_info - **Description**: No description available - **Primary Language**: Unknown - **License**: BSD-3-Clause - **Default Branch**: master - **Homepage**: None - **GVP Project**: No ## Statistics - **Stars**: 0 - **Forks**: 0 - **Created**: 2021-03-19 - **Last Updated**: 2025-08-24 ## Categories & Tags **Categories**: Uncategorized **Tags**: None ## README ## Repo deprecation notice **NOTE**: This repository as been deprecated, as the source code now lives here: https://github.com/dart-lang/sdk/tree/master/pkg/dart2js_info # Dart2js Info This package contains libraries and tools you can use to process info files produced when running dart2js with `--dump-info`. The info files contain data about each element included in the output of your program. The data includes information such as: * the size that each function adds to the `.dart.js` output, * dependencies between functions, * how the code is clustered when using deferred libraries, and * the declared and inferred type of each function argument. All of this information can help you understand why some piece of code is included in your compiled application, and how far was dart2js able to understand your code. This data can help you make changes to improve the quality and size of your framework or app. This package focuses on gathering libraries and tools that summarize all of that information. Bear in mind that even with all these tools, it is not trivial to isolate code-size issues. We just hope that these tools make things a bit easier. ## Status [![Build Status](https://github.com/dart-lang/dart2js_info/workflows/Dart%20CI/badge.svg)](https://github.com/dart-lang/dart2js_info/actions?query=workflow%3A"Dart+CI"+branch%3Amaster) Currently, most tools available here can be used to analyze code-size and attribution of code-size to different parts of your app. With time, we hope to add more data to the info files, and include better tools to help understand the results of type inference. This package is still in flux and we might make breaking changes at any time. Our current goal is not to provide a stable API, we mainly want to expose the functionality and iterate on it. We recommend that you pin a specific version of this package and update when needed. ## Tools All tools are provided as commands of a single command-line interface. To install: ```console pub global activate dart2js_info ``` To run a tool, then run: ```console dart2js_info [arguments] ``` There is a short help available on the tool, and more details are provided below. ## Format There are several formats of info files. Dart2js today produces a JSON format, but very soon will switch to produce a binary format by default. ## Info API This package also exposes libraries to parse and represent the information from the info files. If there is data that is stored in the info files but not exposed by one of our tools, you may be able to use the info APIs to quickly put together your own tool. [AllInfo][AllInfo] exposes a Dart representation of all of the collected information. There are deserialization libraries in this package to decode any info file produced by the `dart2js` `--dump-info` option. See `lib/binary_serialization.dart` and `lib/json_info_codec.dart` to find the binary and JSON decoders respectively. For convenience, `package:dart2js_info/src/io.dart` also exposes a helper method that can choose, depending on the extension of the info file, whether to deserialize it using the binary or JSON decoder. For example: ```dart import 'dart:convert'; import 'dart:io'; import 'package:dart2js_info/info.dart'; import 'package:dart2js_info/src/io.dart'; main(args) async { var infoPath = args[0]; var info = await infoFromFile(infoPath); ... } ``` ## Available tools The following tools are a available today: * [`code_deps`][code_deps]: simple tool that can answer queries about the dependency between functions and fields in your program. Currently it only supports the `some_path` query, which shows a dependency path from one function to another. * [`diff`][diff]: a tool that diffs two info files and reports which program elements have been added, removed, or changed size. This also tells which elements are no longer deferred or have become deferred. * [`library_size`][library_size]: a tool that shows how much code was attributed to each library. This tool is configurable so it can group data in many ways (e.g. to tally together all libraries that belong to a package, or all libraries that match certain name pattern). * [`deferred_check`][deferred_check]: a tool that verifies that code was split into deferred parts as expected. This tool takes a specification of the expected layout of code into deferred parts, and checks that the output from `dart2js` meets the specification. * [`deferred_size`][deferred_size]: a tool that gives a breakdown of the sizes of the deferred parts of the program. This can show how much of your total code size can be loaded deferred. * [`deferred_layout`][deferred_layout]: a tool that reports which code is included on each output unit. * [`function_size`][function_size]: a tool that shows how much code was attributed to each function. This tool also uses dependency information to compute dominance and reachability data. This information can sometimes help determine how much savings could come if the function was not included in the program. * [`coverage_server`][coverage_server] and [`coverage_analysis`][coverage_analysis]: dart2js has an experimental feature to gather coverage data of your application. The `coverage_log_server` can record this data, and `live_code_size_analysis` can correlate that with the info file, so you determine why code that is not used is being included in your app. * [`convert`][convert]: a tool that converts info files from one format to another. Accepted inputs are JSON or the internal binary form, outputs can be JSON, backward-compatible JSON, binary, or protobuf schema (as defined in `info.proto`). * [`show`][show]: a tool that dumps info files in a readable text format. Next we describe in detail how to use each of these tools. ### Code deps tool This command-line tool can be used to query for code dependencies. Currently this tool only supports the `some_path` query, which gives you the shortest path for how one function depends on another. Run this tool as follows: ```console # activate is only needed once to install the dart2js_info tool $ pub global activate dart2js_info $ dart2js_info code_deps some_path out.js.info.data main foo ``` The arguments to the query are regular expressions that can be used to select a single element in your program. If your regular expression is too general and has more than one match, this tool will pick the first match and ignore the rest. Regular expressions are matched against a fully qualified element name, which includes the library and class name (if any) that contains it. A typical qualified name is of this form: libraryName::ClassName.elementName If the name of a function your are looking for is unique enough, it might be sufficient to just write that name as your regular expression. ### Diff tool This command-line tool shows a diff between two info files. It can be run as follows: ```console $ pub global activate dart2js_info # only needed once $ dart2js_info diff old.js.info.data new.js.info.data [--summary] ``` The tool gives a breakdown of the difference between the two info files. Here's an example output: ``` total_size_difference -2688 total_added 0 total_removed 2321 total_size_changed -203 total_became_deferred 0 total_no_longer_deferred 0 ADDED (0 bytes) ======================================================================== REMOVED (2321 bytes) ======================================================================== dart:_js_helper::getRuntimeTypeString: 488 bytes dart:_js_helper::substitute: 479 bytes dart:_js_helper::TypeImpl.toString: 421 bytes dart:_js_helper::computeSignature: 204 bytes dart:_js_helper::getRuntimeTypeArguments: 181 bytes dart:_js_helper::extractFunctionTypeObjectFrom: 171 bytes dart:_js_helper::getTypeArgumentByIndex: 147 bytes dart:_js_helper::runtimeTypeToString: 136 bytes dart:_js_helper::setRuntimeTypeInfo: 94 bytes dart:core::Object.runtimeType: 0 bytes dart:_js_helper::getRawRuntimeType: 0 bytes dart:_js_helper::invoke: 0 bytes dart:_js_helper::invokeOn: 0 bytes dart:_js_helper::getField: 0 bytes dart:_js_helper::getClassName: 0 bytes dart:_js_helper::getRuntimeType: 0 bytes dart:_js_helper::TypeImpl.TypeImpl: 0 bytes CHANGED SIZE (-203 bytes) ======================================================================== dart:_interceptors::JSUnmodifiableArray: -3 bytes dart:core::List: -3 bytes dart:_interceptors::ArrayIterator: -4 bytes dart:_js_helper::TypeImpl._typeName: -10 bytes dart:_js_helper::TypeImpl._unmangledName: -15 bytes dart:_js_names::: -30 bytes dart:_js_names::extractKeys: -30 bytes dart:core::StringBuffer: -40 bytes dart:core::StringBuffer._writeAll: -40 bytes dart:core::: -43 bytes dart:_interceptors::JSArray.+: -63 bytes dart:_interceptors::JSArray: -66 bytes dart:_interceptors::: -73 bytes dart:_js_helper::TypeImpl: -481 bytes dart:_js_helper::: -2445 bytes BECAME DEFERRED (0 bytes) ======================================================================== NO LONGER DEFERRED (0 bytes) ======================================================================== ``` You can also pass `--summary` to only show the summary section. ### Library size split tool This command-line tool shows the size distribution of generated code among libraries. It can be run as follows: ```console $ pub global activate dart2js_info # only needed once $ dart2js_info library_size out.js.info.data ``` Libraries can be grouped using regular expressions. You can specify what regular expressions to use by providing a `grouping.yaml` file with the `--grouping` flag: ```console $ dart2js_info library_size out.js.info.data --grouping grouping.yaml ``` The format of the `grouping.yaml` file is as follows: ```yaml groups: - { regexp: "package:(foo)/*.dart", name: "group name 1", cluster: 2} - { regexp: "dart:.*", name: "group name 2", cluster: 3} ``` The file should include a single key `groups` containing a list of group specifications. Each group is specified by a map of 3 entries: * `regexp` (required): a regexp used to match entries that belong to the group. * `name` (optional): the name given to this group in the output table. If omitted, the name is derived from the regexp as the match's group(1) or group(0) if no group was defined. When names are omitted the group specification implicitly defines several groups, one per observed name. * `cluster` (optional): a clustering index for how data is shown in a table. Groups with higher cluster indices are shown later in the table after a dividing line. If missing, the cluster index defaults to 0. Here is an example configuration, with comments about what each entry does: ```yaml groups: # This group shows the total size for all libraries that were loaded from # file:// urls, it is shown in cluster #2, which happens to be the last # cluster in this example before the totals are shown: - name: "Loose files" regexp: "file://.*" cluster: 2 # This group shows the total size of all code loaded from packages: - { name: "All packages", regexp: "package:.*", cluster: 2} # This group shows the total size of all code loaded from core libraries: - { name: "Core libs", regexp: "dart:.*", cluster: 2} # This group shows the total size of all libraries in a single package. Here # we omitted the `name` entry, instead we extract it from the regexp # directly. In this case, the name will be the package-name portion of the # package-url (determined by group(1) of the regexp). - { regexp: "package:([^/]*)", cluster: 1} # The next two groups match the entire library url as the name of the group. - regexp: "package:.*" - regexp: "dart:.*" # If your code lives under /my/project/dir, this will match any file loaded from a file:// url, and we use as a name the relative path to it. - regexp: "file:///my/project/dir/(.*)" ``` Regardless of the grouping configuration, the tool will display the total code size attributed of all libraries, constants, and the program size. **Note**: eventually you should expect all numbers to add up to the program size. Currently dart2js's `--dump-info` is not complete, so numbers for bootstrapping code and lazy static initializers are missing. ### Deferred library verification This tool checks that the output from dart2js meets a given specification, given in a YAML file. It can be run as follows: ```console $ pub global activate dart2js_info # only needed once $ dart2js_info deferred_check out.js.info.data manifest.yaml ``` The format of the YAML file is: ```yaml main: include: - some_package - other_package exclude: - some_other_package foo: include: - foo - bar baz: include: - baz - quux exclude: - zardoz ``` The YAML file consists of a list of declarations, one for each deferred part expected in the output. At least one of these parts must be named "main"; this is the main part that contains the program entrypoint. Each top-level part contains a list of package names that are expected to be contained in that part, a list of package names that are expected to be in another part, or both. For instance, in the example YAML above the part named "baz" is expected to contain the packages "baz" and "quux" and exclude the package "zardoz". The names for parts given in the specification YAML file (besides "main") are the same as the name given to the deferred import in the dart file. For instance, if you have `import 'package:foo/bar.dart' deferred as baz;` in your dart file, then the corresponding name in the specification file is 'baz'. ### Deferred library size tool This tool gives a breakdown of all of the deferred code in the program by size. It can show how much of the total code size is deferred. It can be run as follows: ```console pub global activate dart2js_info # only needed once dart2js_info deferred_size out.js.info.data ``` The tool will output a table listing all of the deferred imports in the program as well as the "main" chunk, which is not deferred. The output looks like: ``` Size by library ------------------------------------------------ main 12345678 foo 7654321 bar 1234567 ------------------------------------------------ Main chunk size 12345678 Deferred code size 8888888 Percent of code deferred 41.86% ``` ### Deferred library layout tool This tool reports which code is included in each output unit. It can be run as follows: ```console $ pub global activate dart2js_info # only needed once $ dart2js_info deferred_layout out.js.info.data ``` The tool will output a table listing all of the deferred output units or chunks, for each unit it will list the set of libraries that contribute code to this unit. If a library contributes to more than one output unit, the tool lists which elements are in one or another output unit. For example, the output might look like this: ``` Output unit main: loaded by default contains: - hello_world.dart - dart:core ... Output unit 2: loaded by importing: [b] contains: - c.dart: - function d - b.dart Output unit 1: loaded by importing: [a] contains: - c.dart: - function c - a.dart ``` In this example, all the code of `b.dart` after tree-shaking was included in the output unit 2, but `c.dart` was split between output unit 1 and output unit 2. ### Function size analysis tool This command-line tool presents how much each function contributes to the total code of your application. We use dependency information to compute dominance and reachability data as well. When you run: ```console $ pub global activate dart2js_info # only needed once $ dart2js_info function_size out.js.info.data ``` the tool produces a table output with lots of entries. Here is an example entry with the corresponding table header: ``` --- Results per element (field or function) --- element size dominated size reachable size Element identifier ... 275 0.01% 283426 13.97% 1506543 74.28% some.library.name::ClassName.myMethodName ``` Such entry means that the function `myMethodName` uses 275 bytes, which is 0.01% of the application. That function however calls other functions, which transitively can include up to 74.28% of the application size. Of all those reachable functions, some of them are reachable from other parts of the program, but a subset are dominated by `myMethodName`, that is, other parts of the program starting from `main` would first go through `myMethodName` before reaching those functions. In this example, that subset is 13.97% of the application size. This means that if you somehow can remove your dependency on `myMethodName`, you will save at least that 13.97%, and possibly some more from the reachable size, but how much of that we are not certain. ### Coverage tools Coverage information requires a bit more setup and work to get them running. The steps are as follows: * Compile an app with dart2js using `--dump-info` and `--experiment-call-instrumentation` ```console $ dart2js --dump-info --experiment-call-instrumentation main.dart ``` The flag only works dart2js version 2.2.0 or newer. * Launch the coverage server tool to serve up the JS code of your app: ```console $ dart2js_info coverage_server main.dart.js ``` * (optional) If you have a complex application setup, you may need to serve an html file or integrate your application server to proxy to the log server any GET request for the .dart.js file and /coverage POST requests that send coverage data. * Load your app and use it to exercise the entire code. * Shut down the coverage server (Ctrl-C). This will emit a file named `mail.dart.js.coverage.json` * Finally, run the live code analysis tool given it both the info and coverage json files: ```console $ dart2js_info coverage_analysis main.dart.info.data main.dart.coverage.json ``` ## Code location, features and bugs This package is developed in [github][repo]. Please file feature requests and bugs at the [issue tracker][tracker]. [repo]: https://github.com/dart-lang/dart2js_info/ [tracker]: https://github.com/dart-lang/dart2js_info/issues [code_deps]: https://github.com/dart-lang/dart2js_info/blob/master/bin/code_deps.dart [diff]: https://github.com/dart-lang/dart2js_info/blob/master/bin/diff.dart [library_size]: https://github.com/dart-lang/dart2js_info/blob/master/bin/library_size_split.dart [deferred_check]: https://github.com/dart-lang/dart2js_info/blob/master/bin/deferred_library_check.dart [deferred_size]: https://github.com/dart-lang/dart2js_info/blob/master/bin/deferred_library_size.dart [deferred_layout]: https://github.com/dart-lang/dart2js_info/blob/master/bin/deferred_library_layout.dart [coverage_server]: https://github.com/dart-lang/dart2js_info/blob/master/bin/coverage_log_server.dart [coverage_analysis]: https://github.com/dart-lang/dart2js_info/blob/master/bin/live_code_size_analysis.dart [function_size]: https://github.com/dart-lang/dart2js_info/blob/master/bin/function_size_analysis.dart [AllInfo]: http://dart-lang.github.io/dart2js_info/doc/api/dart2js_info.info/AllInfo-class.html [convert]: https://github.com/dart-lang/dart2js_info/blob/master/bin/convert.dart [show]: https://github.com/dart-lang/dart2js_info/blob/master/bin/text_print.dart