CONTRIBUTING.md (22783B) - raw


      1 **Please include the full output of youtube-dl when run with `-v`**, i.e. **add** `-v` flag to **your command line**, copy the **whole** output and post it in the issue body wrapped in \`\`\` for better formatting. It should look similar to this:
      2 ```
      3 $ youtube-dl -v <your command line>
      4 [debug] System config: []
      5 [debug] User config: []
      6 [debug] Command-line args: [u'-v', u'https://www.youtube.com/watch?v=BaW_jenozKcj']
      7 [debug] Encodings: locale cp1251, fs mbcs, out cp866, pref cp1251
      8 [debug] youtube-dl version 2015.12.06
      9 [debug] Git HEAD: 135392e
     10 [debug] Python version 2.6.6 - Windows-2003Server-5.2.3790-SP2
     11 [debug] exe versions: ffmpeg N-75573-g1d0487f, ffprobe N-75573-g1d0487f, rtmpdump 2.4
     12 [debug] Proxy map: {}
     13 ...
     14 ```
     15 **Do not post screenshots of verbose logs; only plain text is acceptable.**
     16 
     17 The output (including the first lines) contains important debugging information. Issues without the full output are often not reproducible and therefore do not get solved in short order, if ever.
     18 
     19 Please re-read your issue once again to avoid a couple of common mistakes (you can and should use this as a checklist):
     20 
     21 ### Is the description of the issue itself sufficient?
     22 
     23 We often get issue reports that we cannot really decipher. While in most cases we eventually get the required information after asking back multiple times, this poses an unnecessary drain on our resources. Many contributors, including myself, are also not native speakers, so we may misread some parts.
     24 
     25 So please elaborate on what feature you are requesting, or what bug you want to be fixed. Make sure that it's obvious
     26 
     27 - What the problem is
     28 - How it could be fixed
     29 - How your proposed solution would look like
     30 
     31 If your report is shorter than two lines, it is almost certainly missing some of these, which makes it hard for us to respond to it. We're often too polite to close the issue outright, but the missing info makes misinterpretation likely. As a committer myself, I often get frustrated by these issues, since the only possible way for me to move forward on them is to ask for clarification over and over.
     32 
     33 For bug reports, this means that your report should contain the *complete* output of youtube-dl when called with the `-v` flag. The error message you get for (most) bugs even says so, but you would not believe how many of our bug reports do not contain this information.
     34 
     35 If your server has multiple IPs or you suspect censorship, adding `--call-home` may be a good idea to get more diagnostics. If the error is `ERROR: Unable to extract ...` and you cannot reproduce it from multiple countries, add `--dump-pages` (warning: this will yield a rather large output, redirect it to the file `log.txt` by adding `>log.txt 2>&1` to your command-line) or upload the `.dump` files you get when you add `--write-pages` [somewhere](https://gist.github.com/).
     36 
     37 **Site support requests must contain an example URL**. An example URL is a URL you might want to download, like `https://www.youtube.com/watch?v=BaW_jenozKc`. There should be an obvious video present. Except under very special circumstances, the main page of a video service (e.g. `https://www.youtube.com/`) is *not* an example URL.
     38 
     39 ###  Are you using the latest version?
     40 
     41 Before reporting any issue, type `youtube-dl -U`. This should report that you're up-to-date. About 20% of the reports we receive are already fixed, but people are using outdated versions. This goes for feature requests as well.
     42 
     43 ###  Is the issue already documented?
     44 
     45 Make sure that someone has not already opened the issue you're trying to open. Search at the top of the window or browse the [GitHub Issues](https://github.com/ytdl-org/youtube-dl/search?type=Issues) of this repository. If there is an issue, feel free to write something along the lines of "This affects me as well, with version 2015.01.01. Here is some more information on the issue: ...". While some issues may be old, a new post into them often spurs rapid activity.
     46 
     47 ###  Why are existing options not enough?
     48 
     49 Before requesting a new feature, please have a quick peek at [the list of supported options](https://github.com/ytdl-org/youtube-dl/blob/master/README.md#options). Many feature requests are for features that actually exist already! Please, absolutely do show off your work in the issue report and detail how the existing similar options do *not* solve your problem.
     50 
     51 ###  Is there enough context in your bug report?
     52 
     53 People want to solve problems, and often think they do us a favor by breaking down their larger problems (e.g. wanting to skip already downloaded files) to a specific request (e.g. requesting us to look whether the file exists before downloading the info page). However, what often happens is that they break down the problem into two steps: One simple, and one impossible (or extremely complicated one).
     54 
     55 We are then presented with a very complicated request when the original problem could be solved far easier, e.g. by recording the downloaded video IDs in a separate file. To avoid this, you must include the greater context where it is non-obvious. In particular, every feature request that does not consist of adding support for a new site should contain a use case scenario that explains in what situation the missing feature would be useful.
     56 
     57 ###  Does the issue involve one problem, and one problem only?
     58 
     59 Some of our users seem to think there is a limit of issues they can or should open. There is no limit of issues they can or should open. While it may seem appealing to be able to dump all your issues into one ticket, that means that someone who solves one of your issues cannot mark the issue as closed. Typically, reporting a bunch of issues leads to the ticket lingering since nobody wants to attack that behemoth, until someone mercifully splits the issue into multiple ones.
     60 
     61 In particular, every site support request issue should only pertain to services at one site (generally under a common domain, but always using the same backend technology). Do not request support for vimeo user videos, White house podcasts, and Google Plus pages in the same issue. Also, make sure that you don't post bug reports alongside feature requests. As a rule of thumb, a feature request does not include outputs of youtube-dl that are not immediately related to the feature at hand. Do not post reports of a network error alongside the request for a new video service.
     62 
     63 ###  Is anyone going to need the feature?
     64 
     65 Only post features that you (or an incapacitated friend you can personally talk to) require. Do not post features because they seem like a good idea. If they are really useful, they will be requested by someone who requires them.
     66 
     67 ###  Is your question about youtube-dl?
     68 
     69 It may sound strange, but some bug reports we receive are completely unrelated to youtube-dl and relate to a different, or even the reporter's own, application. Please make sure that you are actually using youtube-dl. If you are using a UI for youtube-dl, report the bug to the maintainer of the actual application providing the UI. On the other hand, if your UI for youtube-dl fails in some way you believe is related to youtube-dl, by all means, go ahead and report the bug.
     70 
     71 # DEVELOPER INSTRUCTIONS
     72 
     73 Most users do not need to build youtube-dl and can [download the builds](https://ytdl-org.github.io/youtube-dl/download.html) or get them from their distribution.
     74 
     75 To run youtube-dl as a developer, you don't need to build anything either. Simply execute
     76 
     77     python -m youtube_dl
     78 
     79 To run the test, simply invoke your favorite test runner, or execute a test file directly; any of the following work:
     80 
     81     python -m unittest discover
     82     python test/test_download.py
     83     nosetests
     84 
     85 See item 6 of [new extractor tutorial](#adding-support-for-a-new-site) for how to run extractor specific test cases.
     86 
     87 If you want to create a build of youtube-dl yourself, you'll need
     88 
     89 * python
     90 * make (only GNU make is supported)
     91 * pandoc
     92 * zip
     93 * nosetests
     94 
     95 ### Adding support for a new site
     96 
     97 If you want to add support for a new site, first of all **make sure** this site is **not dedicated to [copyright infringement](README.md#can-you-add-support-for-this-anime-video-site-or-site-which-shows-current-movies-for-free)**. youtube-dl does **not support** such sites thus pull requests adding support for them **will be rejected**.
     98 
     99 After you have ensured this site is distributing its content legally, you can follow this quick list (assuming your service is called `yourextractor`):
    100 
    101 1. [Fork this repository](https://github.com/ytdl-org/youtube-dl/fork)
    102 2. Check out the source code with:
    103 
    104         git clone git@github.com:YOUR_GITHUB_USERNAME/youtube-dl.git
    105 
    106 3. Start a new git branch with
    107 
    108         cd youtube-dl
    109         git checkout -b yourextractor
    110 
    111 4. Start with this simple template and save it to `youtube_dl/extractor/yourextractor.py`:
    112 
    113     ```python
    114     # coding: utf-8
    115     from __future__ import unicode_literals
    116 
    117     from .common import InfoExtractor
    118 
    119 
    120     class YourExtractorIE(InfoExtractor):
    121         _VALID_URL = r'https?://(?:www\.)?yourextractor\.com/watch/(?P<id>[0-9]+)'
    122         _TEST = {
    123             'url': 'https://yourextractor.com/watch/42',
    124             'md5': 'TODO: md5 sum of the first 10241 bytes of the video file (use --test)',
    125             'info_dict': {
    126                 'id': '42',
    127                 'ext': 'mp4',
    128                 'title': 'Video title goes here',
    129                 'thumbnail': r're:^https?://.*\.jpg$',
    130                 # TODO more properties, either as:
    131                 # * A value
    132                 # * MD5 checksum; start the string with md5:
    133                 # * A regular expression; start the string with re:
    134                 # * Any Python type (for example int or float)
    135             }
    136         }
    137 
    138         def _real_extract(self, url):
    139             video_id = self._match_id(url)
    140             webpage = self._download_webpage(url, video_id)
    141 
    142             # TODO more code goes here, for example ...
    143             title = self._html_search_regex(r'<h1>(.+?)</h1>', webpage, 'title')
    144 
    145             return {
    146                 'id': video_id,
    147                 'title': title,
    148                 'description': self._og_search_description(webpage),
    149                 'uploader': self._search_regex(r'<div[^>]+id="uploader"[^>]*>([^<]+)<', webpage, 'uploader', fatal=False),
    150                 # TODO more properties (see youtube_dl/extractor/common.py)
    151             }
    152     ```
    153 5. Add an import in [`youtube_dl/extractor/extractors.py`](https://github.com/ytdl-org/youtube-dl/blob/master/youtube_dl/extractor/extractors.py).
    154 6. Run `python test/test_download.py TestDownload.test_YourExtractor`. This *should fail* at first, but you can continually re-run it until you're done. If you decide to add more than one test, then rename ``_TEST`` to ``_TESTS`` and make it into a list of dictionaries. The tests will then be named `TestDownload.test_YourExtractor`, `TestDownload.test_YourExtractor_1`, `TestDownload.test_YourExtractor_2`, etc. Note that tests with `only_matching` key in test's dict are not counted in.
    155 7. Have a look at [`youtube_dl/extractor/common.py`](https://github.com/ytdl-org/youtube-dl/blob/master/youtube_dl/extractor/common.py) for possible helper methods and a [detailed description of what your extractor should and may return](https://github.com/ytdl-org/youtube-dl/blob/7f41a598b3fba1bcab2817de64a08941200aa3c8/youtube_dl/extractor/common.py#L94-L303). Add tests and code for as many as you want.
    156 8. Make sure your code follows [youtube-dl coding conventions](#youtube-dl-coding-conventions) and check the code with [flake8](https://flake8.pycqa.org/en/latest/index.html#quickstart):
    157 
    158         $ flake8 youtube_dl/extractor/yourextractor.py
    159 
    160 9. Make sure your code works under all [Python](https://www.python.org/) versions claimed supported by youtube-dl, namely 2.6, 2.7, and 3.2+.
    161 10. When the tests pass, [add](https://git-scm.com/docs/git-add) the new files and [commit](https://git-scm.com/docs/git-commit) them and [push](https://git-scm.com/docs/git-push) the result, like this:
    162 
    163         $ git add youtube_dl/extractor/extractors.py
    164         $ git add youtube_dl/extractor/yourextractor.py
    165         $ git commit -m '[yourextractor] Add new extractor'
    166         $ git push origin yourextractor
    167 
    168 11. Finally, [create a pull request](https://help.github.com/articles/creating-a-pull-request). We'll then review and merge it.
    169 
    170 In any case, thank you very much for your contributions!
    171 
    172 ## youtube-dl coding conventions
    173 
    174 This section introduces a guide lines for writing idiomatic, robust and future-proof extractor code.
    175 
    176 Extractors are very fragile by nature since they depend on the layout of the source data provided by 3rd party media hosters out of your control and this layout tends to change. As an extractor implementer your task is not only to write code that will extract media links and metadata correctly but also to minimize dependency on the source's layout and even to make the code foresee potential future changes and be ready for that. This is important because it will allow the extractor not to break on minor layout changes thus keeping old youtube-dl versions working. Even though this breakage issue is easily fixed by emitting a new version of youtube-dl with a fix incorporated, all the previous versions become broken in all repositories and distros' packages that may not be so prompt in fetching the update from us. Needless to say, some non rolling release distros may never receive an update at all.
    177 
    178 ### Mandatory and optional metafields
    179 
    180 For extraction to work youtube-dl relies on metadata your extractor extracts and provides to youtube-dl expressed by an [information dictionary](https://github.com/ytdl-org/youtube-dl/blob/7f41a598b3fba1bcab2817de64a08941200aa3c8/youtube_dl/extractor/common.py#L94-L303) or simply *info dict*. Only the following meta fields in the *info dict* are considered mandatory for a successful extraction process by youtube-dl:
    181 
    182  - `id` (media identifier)
    183  - `title` (media title)
    184  - `url` (media download URL) or `formats`
    185 
    186 In fact only the last option is technically mandatory (i.e. if you can't figure out the download location of the media the extraction does not make any sense). But by convention youtube-dl also treats `id` and `title` as mandatory. Thus the aforementioned metafields are the critical data that the extraction does not make any sense without and if any of them fail to be extracted then the extractor is considered completely broken.
    187 
    188 [Any field](https://github.com/ytdl-org/youtube-dl/blob/7f41a598b3fba1bcab2817de64a08941200aa3c8/youtube_dl/extractor/common.py#L188-L303) apart from the aforementioned ones are considered **optional**. That means that extraction should be **tolerant** to situations when sources for these fields can potentially be unavailable (even if they are always available at the moment) and **future-proof** in order not to break the extraction of general purpose mandatory fields.
    189 
    190 #### Example
    191 
    192 Say you have some source dictionary `meta` that you've fetched as JSON with HTTP request and it has a key `summary`:
    193 
    194 ```python
    195 meta = self._download_json(url, video_id)
    196 ```
    197     
    198 Assume at this point `meta`'s layout is:
    199 
    200 ```python
    201 {
    202     ...
    203     "summary": "some fancy summary text",
    204     ...
    205 }
    206 ```
    207 
    208 Assume you want to extract `summary` and put it into the resulting info dict as `description`. Since `description` is an optional meta field you should be ready that this key may be missing from the `meta` dict, so that you should extract it like:
    209 
    210 ```python
    211 description = meta.get('summary')  # correct
    212 ```
    213 
    214 and not like:
    215 
    216 ```python
    217 description = meta['summary']  # incorrect
    218 ```
    219 
    220 The latter will break extraction process with `KeyError` if `summary` disappears from `meta` at some later time but with the former approach extraction will just go ahead with `description` set to `None` which is perfectly fine (remember `None` is equivalent to the absence of data).
    221 
    222 Similarly, you should pass `fatal=False` when extracting optional data from a webpage with `_search_regex`, `_html_search_regex` or similar methods, for instance:
    223 
    224 ```python
    225 description = self._search_regex(
    226     r'<span[^>]+id="title"[^>]*>([^<]+)<',
    227     webpage, 'description', fatal=False)
    228 ```
    229 
    230 With `fatal` set to `False` if `_search_regex` fails to extract `description` it will emit a warning and continue extraction.
    231 
    232 You can also pass `default=<some fallback value>`, for example:
    233 
    234 ```python
    235 description = self._search_regex(
    236     r'<span[^>]+id="title"[^>]*>([^<]+)<',
    237     webpage, 'description', default=None)
    238 ```
    239 
    240 On failure this code will silently continue the extraction with `description` set to `None`. That is useful for metafields that may or may not be present.
    241  
    242 ### Provide fallbacks
    243 
    244 When extracting metadata try to do so from multiple sources. For example if `title` is present in several places, try extracting from at least some of them. This makes it more future-proof in case some of the sources become unavailable.
    245 
    246 #### Example
    247 
    248 Say `meta` from the previous example has a `title` and you are about to extract it. Since `title` is a mandatory meta field you should end up with something like:
    249 
    250 ```python
    251 title = meta['title']
    252 ```
    253 
    254 If `title` disappears from `meta` in future due to some changes on the hoster's side the extraction would fail since `title` is mandatory. That's expected.
    255 
    256 Assume that you have some another source you can extract `title` from, for example `og:title` HTML meta of a `webpage`. In this case you can provide a fallback scenario:
    257 
    258 ```python
    259 title = meta.get('title') or self._og_search_title(webpage)
    260 ```
    261 
    262 This code will try to extract from `meta` first and if it fails it will try extracting `og:title` from a `webpage`.
    263 
    264 ### Regular expressions
    265 
    266 #### Don't capture groups you don't use
    267 
    268 Capturing group must be an indication that it's used somewhere in the code. Any group that is not used must be non capturing.
    269 
    270 ##### Example
    271 
    272 Don't capture id attribute name here since you can't use it for anything anyway.
    273 
    274 Correct:
    275 
    276 ```python
    277 r'(?:id|ID)=(?P<id>\d+)'
    278 ```
    279 
    280 Incorrect:
    281 ```python
    282 r'(id|ID)=(?P<id>\d+)'
    283 ```
    284 
    285 
    286 #### Make regular expressions relaxed and flexible
    287 
    288 When using regular expressions try to write them fuzzy, relaxed and flexible, skipping insignificant parts that are more likely to change, allowing both single and double quotes for quoted values and so on.
    289  
    290 ##### Example
    291 
    292 Say you need to extract `title` from the following HTML code:
    293 
    294 ```html
    295 <span style="position: absolute; left: 910px; width: 90px; float: right; z-index: 9999;" class="title">some fancy title</span>
    296 ```
    297 
    298 The code for that task should look similar to:
    299 
    300 ```python
    301 title = self._search_regex(
    302     r'<span[^>]+class="title"[^>]*>([^<]+)', webpage, 'title')
    303 ```
    304 
    305 Or even better:
    306 
    307 ```python
    308 title = self._search_regex(
    309     r'<span[^>]+class=(["\'])title\1[^>]*>(?P<title>[^<]+)',
    310     webpage, 'title', group='title')
    311 ```
    312 
    313 Note how you tolerate potential changes in the `style` attribute's value or switch from using double quotes to single for `class` attribute: 
    314 
    315 The code definitely should not look like:
    316 
    317 ```python
    318 title = self._search_regex(
    319     r'<span style="position: absolute; left: 910px; width: 90px; float: right; z-index: 9999;" class="title">(.*?)</span>',
    320     webpage, 'title', group='title')
    321 ```
    322 
    323 ### Long lines policy
    324 
    325 There is a soft limit to keep lines of code under 80 characters long. This means it should be respected if possible and if it does not make readability and code maintenance worse.
    326 
    327 For example, you should **never** split long string literals like URLs or some other often copied entities over multiple lines to fit this limit:
    328 
    329 Correct:
    330 
    331 ```python
    332 'https://www.youtube.com/watch?v=FqZTN594JQw&list=PLMYEtVRpaqY00V9W81Cwmzp6N6vZqfUKD4'
    333 ```
    334 
    335 Incorrect:
    336 
    337 ```python
    338 'https://www.youtube.com/watch?v=FqZTN594JQw&list='
    339 'PLMYEtVRpaqY00V9W81Cwmzp6N6vZqfUKD4'
    340 ```
    341 
    342 ### Inline values
    343 
    344 Extracting variables is acceptable for reducing code duplication and improving readability of complex expressions. However, you should avoid extracting variables used only once and moving them to opposite parts of the extractor file, which makes reading the linear flow difficult.
    345 
    346 #### Example
    347 
    348 Correct:
    349 
    350 ```python
    351 title = self._html_search_regex(r'<title>([^<]+)</title>', webpage, 'title')
    352 ```
    353 
    354 Incorrect:
    355 
    356 ```python
    357 TITLE_RE = r'<title>([^<]+)</title>'
    358 # ...some lines of code...
    359 title = self._html_search_regex(TITLE_RE, webpage, 'title')
    360 ```
    361 
    362 ### Collapse fallbacks
    363 
    364 Multiple fallback values can quickly become unwieldy. Collapse multiple fallback values into a single expression via a list of patterns.
    365 
    366 #### Example
    367 
    368 Good:
    369 
    370 ```python
    371 description = self._html_search_meta(
    372     ['og:description', 'description', 'twitter:description'],
    373     webpage, 'description', default=None)
    374 ```
    375 
    376 Unwieldy:
    377 
    378 ```python
    379 description = (
    380     self._og_search_description(webpage, default=None)
    381     or self._html_search_meta('description', webpage, default=None)
    382     or self._html_search_meta('twitter:description', webpage, default=None))
    383 ```
    384 
    385 Methods supporting list of patterns are: `_search_regex`, `_html_search_regex`, `_og_search_property`, `_html_search_meta`.
    386 
    387 ### Trailing parentheses
    388 
    389 Always move trailing parentheses after the last argument.
    390 
    391 #### Example
    392 
    393 Correct:
    394 
    395 ```python
    396     lambda x: x['ResultSet']['Result'][0]['VideoUrlSet']['VideoUrl'],
    397     list)
    398 ```
    399 
    400 Incorrect:
    401 
    402 ```python
    403     lambda x: x['ResultSet']['Result'][0]['VideoUrlSet']['VideoUrl'],
    404     list,
    405 )
    406 ```
    407 
    408 ### Use convenience conversion and parsing functions
    409 
    410 Wrap all extracted numeric data into safe functions from [`youtube_dl/utils.py`](https://github.com/ytdl-org/youtube-dl/blob/master/youtube_dl/utils.py): `int_or_none`, `float_or_none`. Use them for string to number conversions as well.
    411 
    412 Use `url_or_none` for safe URL processing.
    413 
    414 Use `try_get` for safe metadata extraction from parsed JSON.
    415 
    416 Use `unified_strdate` for uniform `upload_date` or any `YYYYMMDD` meta field extraction, `unified_timestamp` for uniform `timestamp` extraction, `parse_filesize` for `filesize` extraction, `parse_count` for count meta fields extraction, `parse_resolution`, `parse_duration` for `duration` extraction, `parse_age_limit` for `age_limit` extraction. 
    417 
    418 Explore [`youtube_dl/utils.py`](https://github.com/ytdl-org/youtube-dl/blob/master/youtube_dl/utils.py) for more useful convenience functions.
    419 
    420 #### More examples
    421 
    422 ##### Safely extract optional description from parsed JSON
    423 ```python
    424 description = try_get(response, lambda x: x['result']['video'][0]['summary'], compat_str)
    425 ```
    426 
    427 ##### Safely extract more optional metadata
    428 ```python
    429 video = try_get(response, lambda x: x['result']['video'][0], dict) or {}
    430 description = video.get('summary')
    431 duration = float_or_none(video.get('durationMs'), scale=1000)
    432 view_count = int_or_none(video.get('views'))
    433 ```
    434