mirror of
https://github.com/shaka-project/shaka-player.git
synced 2026-06-15 16:06:41 +03:00
Joey Parrish
1076b78465
The Closure Library's base.js, the Closure Compiler, and the Closure deps-writer are all now loaded via NPM instead of commiting them directly to the repo. This also updates both the library and compiler to the latest version: 20200406. We still have a fork of the Closure Library's URI parser. The latest upstream version of that has too many dependencies on the rest of the library to import directly from NPM. Some internals of the build system have been refactored, and the "complete" set of files in the build system now includes third_party. Our forked URI parser does not pass lint checks yet, so the linter does not run over third_party yet. A couple of overly-severe sets of compiler checks have been disabled, since even the latest Closure Library's base.js doesn't pass them. The script-loader in load.js had to be updated for compatibility with the new Closure Library. If you don't return "true" now, Closure's base.js will stop loading subsequent source files. Some local externs that we had written are now available from the compiler, so our local copies have been deleted. A few type-related changes have been made as well, removing casts that were necessary with the old compiler, but not necessary with the new one. Finally, this corrects some type issues in the tests using the new "typeof" annotation from the compiler. This allows us to type a variable as a class defined elsewhere. For example, after loading the compiled library, we can reference compiledShaka.Player, which has the type "typeof shaka.Player". The compiler can then type-check all uses of it in the tests. Closes #2528 (bad polyfill code generated by the old compiler) Change-Id: I62ec61e82d4edf342b2c576c2d4f89f11562ee65
195 lines
6.5 KiB
Markdown
195 lines
6.5 KiB
Markdown
# Debugging
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#### Create an error
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Let's say that we have some kind of error, and we want to debug it.
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To simulate this, we'll start with the code from {@tutorial basic-usage}
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and make a bad change.
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First, let's change `manifestUri` by removing the last letter.
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```js
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var manifestUri =
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'https://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mp';
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```
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Now reload the page. This causes an error in the JS console that says "Error
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code 1001".
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#### Looking up error codes
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Look at the Error we just logged. It has `category: 1`, `code: 1001`. To find
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out what that means, check the docs for {@link shaka.util.Error}. There we find
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that `1001` means `BAD_HTTP_STATUS`:
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> An HTTP network request returned an HTTP status that indicated a failure.
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> error.data[0] is the URI.
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> ...
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So some HTTP request failed, and we can see the failed URI in `data[0]`.
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#### Loading the debug library
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The compiled library has no usable stack traces and no logging. So to get more
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information, we need to switch to the debug library. The debug library is still
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compiled into a single bundle, but logging and other debug features are enabled.
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To load the debug version of the library instead of the compiled version, just
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change "compiled.js" to "compiled.debug.js" in our HTML file:
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```html
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<head>
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<!-- Shaka Player debug library: -->
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<script src="shaka-player.compiled.debug.js"></script>
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<!-- Your application source: -->
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<script src="myapp.js"></script>
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</head>
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```
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Once we're using the debug library, we will be able to see detailed logs and
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line numbers for errors.
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Reload the page and look in the JavaScript console. Now we see something
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similar to this (formatted a bit differently in the console):
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```js
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HEAD http://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mp 404 (Not Found) http_plugin.js:94
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HEAD http://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mp 404 (Not Found) http_plugin.js:94
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HEAD request to guess manifest type failed! shaka.util.Error manifest_parser.js:179
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Error code 1001 object shaka.util.Error myapp.js:45
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```
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We have a little more information from the library now, and we can expand the
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Error object and see a human-readable message and a stack trace:
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```js
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shaka.util.Error
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category: 1
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code: 1001
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data: Array[3]
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0: "http://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mp"
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1: 404
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2: ""
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length: 3
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message:
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"Shaka Error NETWORK.BAD_HTTP_STATUS (...)"
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stack: "Error: Shaka Error NETWORK.BAD_HTTP_STATUS (http://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mp,404,)
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at new shaka.util.Error (http://localhost/shaka/lib/util/error.js:77:13)
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at XMLHttpRequest.xhr.onload (http://localhost/shaka/lib/net/http_plugin.js:70:16)"
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```
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With the information from the debug library, we have the error name as well as
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the code. So we could avoid looking up the number in the documentation. The
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stack trace gives us clues about where the error was generated, so we can look
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more closely at the source code if we need to.
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#### Setting the log level
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Sometimes the error and stack trace isn't enough. Sometimes you need to see a
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long sequence of events leading up to an error. You may also be asked to attach
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logs as part of a bug report to help the Shaka Player team understand your bug.
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For this, you want to set the log level. The log level lets you control what
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logs are shown by the debug library. To set the log level, add one of these to
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the top of `initApp()` in myapp.js:
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```js
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// Debug logs, when the default of INFO isn't enough:
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shaka.log.setLevel(shaka.log.Level.DEBUG);
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// Verbose logs, which can generate a lot of output:
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shaka.log.setLevel(shaka.log.Level.V1);
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// Verbose 2, which is extremely noisy:
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shaka.log.setLevel(shaka.log.Level.V2);
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```
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Please note that this method is not available from the compiled library.
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If we set the level to `V1` and reload, we get something like this in the
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JavaScript console:
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```js
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HEAD http://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mp 404 (Not Found) http_plugin.js:94
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Unable to find byte-order-mark, making an educated guess. string_utils.js:130
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HTTP error text: http_plugin.js:69
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HEAD http://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mp 404 (Not Found) http_plugin.js:94
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Unable to find byte-order-mark, making an educated guess. string_utils.js:130
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HTTP error text: http_plugin.js:69
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HEAD request to guess manifest type failed! shaka.util.Error manifest_parser.js:179
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load() failed: shaka.util.Error player.js:498
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Error code 1001 object shaka.util.Error myapp.js:48
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```
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So much more information! We can now see that the failed HEAD request caused
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load() to fail.
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#### Advanced: Loading the uncompiled library
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To do rapid testing and development, you can also load the uncompiled library.
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This allows you to edit files and just hit the "reload" button in the browser
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to see changes immediately. This approach is trickier than using the debug
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library, because the entire source tree needs to be available to your web
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server, and because the individual sources can't be moved relative to the files
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in `dist/`.
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Instead of the single-file compiled library, we need to load three scripts in
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our HTML file:
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1. Closure's base library. (This is a small JavaScript library related to the
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Closure compiler used when we build Shaka.) This is what loads Shaka without
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requiring you to list all 50+ source files.
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2. A dependency file which maps Shaka's class names to source files. This is
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how Closure's base library can locate all of Shaka's individual source files.
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3. The uncompiled Shaka library's bootstrap file, "shaka-player.uncompiled.js".
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This uses Closure to load the top-level parts of the library. Each of those
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files in turn load their internal dependencies.
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Once we're using the uncompiled library, we will be able to reload quickly
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without rebuilding.
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```html
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<head>
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<!-- Closure base: -->
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<script src="node_modules/google-closure-library/closure/goog/base.js"></script>
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<!-- Deps file: -->
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<script src="dist/deps.js"></script>
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<!-- Shaka Player uncompiled library: -->
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<script src="shaka-player.uncompiled.js"></script>
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<!-- Your application source: -->
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<script src="myapp.js"></script>
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</head>
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```
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#### Wrap up
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To sum up, remember these points when debugging your application:
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- Use the debug version of Shaka Player for debugging and integration work
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- Refer to the docs for error codes
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- Increase the log level when you need more detail
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#### Continue the Tutorials
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Next, check out {@tutorial config}.
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