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Recommend the use of the debug library
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Instead of using the uncompiled library, which some app developers
have been confused about, recommend the use of the much simpler debug
library, which offers many of the same advantages.

Thanks to @jpmedley for pointing out the complexities of using the
uncompiled build.

Change-Id: I771a2b5a98152a67807629538d8537721177399f
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joeyparrish committed Feb 28, 2018
1 parent def3d57 commit 2d0b300
Showing 1 changed file with 55 additions and 27 deletions.
82 changes: 55 additions & 27 deletions docs/tutorials/debugging.md
Original file line number Diff line number Diff line change
Expand Up @@ -29,40 +29,29 @@ that `1001` means `BAD_HTTP_STATUS`:
So some HTTP request failed, and we can see the failed URI in `data[0]`.


#### Loading the uncompiled library
#### Loading the debug library

The compiled library has no usable stack traces and no logging. So to get more
information, we need to switch to the uncompiled library.
information, we need to switch to the debug library. The debug library is still
compiled into a single bundle, but logging and other debug features are enabled.

Instead of the single-file compiled library, we need to load three scripts in
our HTML file:

1. Closure's base library. (This is a small JavaScript library related to the
Closure compiler used when we build Shaka.) This is what loads Shaka without
requiring you to list all 50+ source files.
2. A dependency file which maps Shaka's class names to source files. This is
how Closure's base library can locate all of Shaka's individual source files.
3. The uncompiled Shaka library's bootstrap file, "shaka-player.uncompiled.js".
This uses Closure to load the top-level parts of the library. Each of those
files in turn load their internal dependencies.

Once we're using the uncompiled library, we will be able to see detailed logs
and line numbers for errors.
To load the debug version of the library instead of the compiled version, just
change "compiled.js" to "compiled.debug.js" in our HTML file:

```html
<head>
<!-- Closure base: -->
<script src="third_party/closure/goog/base.js"></script>
<!-- Deps file: -->
<script src="dist/deps.js"></script>
<!-- Shaka Player uncompiled library: -->
<script src="shaka-player.uncompiled.js"></script>
<!-- Shaka Player debug library: -->
<script src="shaka-player.compiled.debug.js"></script>

<!-- Your application source: -->
<script src="myapp.js"></script>
</head>
```

Once we're using the debug library, we will be able to see detailed logs and
line numbers for errors.


Reload the page and look in the JavaScript console. Now we see something
similar to this (formatted a bit differently in the console):

Expand Down Expand Up @@ -95,8 +84,8 @@ shaka.util.Error
at XMLHttpRequest.xhr.onload (http://localhost/shaka/lib/net/http_plugin.js:70:16)"
```

With the information from the uncompiled library, we have the error name as well
as the code. So we could avoid looking up the number in the documentation. The
With the information from the debug library, we have the error name as well as
the code. So we could avoid looking up the number in the documentation. The
stack trace gives us clues about where the error was generated, so we can look
more closely at the source code if we need to.

Expand All @@ -108,8 +97,8 @@ long sequence of events leading up to an error. You may also be asked to attach
logs as part of a bug report to help the Shaka Player team understand your bug.

For this, you want to set the log level. The log level lets you control what
logs are shown by the uncompiled library. To set the log level, add one of
these to the top of `initApp()` in myapp.js:
logs are shown by the debug library. To set the log level, add one of these to
the top of `initApp()` in myapp.js:

```js
// Debug logs, when the default of INFO isn't enough:
Expand Down Expand Up @@ -151,11 +140,50 @@ So much more information! We can now see that the failed HEAD request caused
load() to fail.


#### Advanced: Loading the uncompiled library

To do rapid testing and development, you can also load the uncompiled library.
This allows you to edit files and just hit the "reload" button in the browser
to see changes immediately. This approach is trickier than using the debug
library, because the entire source tree needs to be available to your web
server, and because the individual sources can't be moved relative to the files
in `dist/`.

Instead of the single-file compiled library, we need to load three scripts in
our HTML file:

1. Closure's base library. (This is a small JavaScript library related to the
Closure compiler used when we build Shaka.) This is what loads Shaka without
requiring you to list all 50+ source files.
2. A dependency file which maps Shaka's class names to source files. This is
how Closure's base library can locate all of Shaka's individual source files.
3. The uncompiled Shaka library's bootstrap file, "shaka-player.uncompiled.js".
This uses Closure to load the top-level parts of the library. Each of those
files in turn load their internal dependencies.

Once we're using the uncompiled library, we will be able to reload quickly
without rebuilding.

```html
<head>
<!-- Closure base: -->
<script src="third_party/closure/goog/base.js"></script>
<!-- Deps file: -->
<script src="dist/deps.js"></script>
<!-- Shaka Player uncompiled library: -->
<script src="shaka-player.uncompiled.js"></script>

<!-- Your application source: -->
<script src="myapp.js"></script>
</head>
```


#### Wrap up

To sum up, remember these points when debugging your application:

- Use the uncompiled version of Shaka Player for debugging and integration work
- Use the debug version of Shaka Player for debugging and integration work
- Refer to the docs for error codes
- Increase the log level when you need more detail

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