package amp.transform

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A Metadata is part of the transformers' response, and includes additional information either not present in or not easily accessible from the HTML. It should remain relatively small, as it undergoes a serialization/deserialization round-trip when the Go library is called from C.

• repeated Metadata.Preload preloads = 1

  Absolute URLs of resources that should be preloaded when the AMP is prefetched. In a signed exchange (SXG) context, these would be included as `Link: rel=preload` headers, as these are used by the browser during SXG prefetch: https://github.com/WICG/webpackage/blob/master/explainer.md#prefetching-stops-here

• int32 max_age_secs = 2

  Recommended validity duration (`expires - date`), in seconds, of the SXG, based on the content being signed. In particular, JS is given a shorter lifetime to reduce risk of issues due to downgrades: https://wicg.github.io/webpackage/draft-yasskin-http-origin-signed-responses.html#seccons-downgrades.

Used in: Metadata

• string url = 1

  The URL of the resource to preload. Will be an absolute URL on the domain of the target AMP cache.

• string as = 2

  The `as` attribute of the preload, as specified in https://w3c.github.io/preload/#as-attribute and https://html.spec.whatwg.org/multipage/semantics.html#attr-link-as. The full list of potential values is specified in https://fetch.spec.whatwg.org/#concept-request-destination, though for the time being only "script", "style", and "image" are allowed.

• string media = 3

  The media attribute for image preload link. This attribute is useful only for image links. Deprecated, instead use the `attributes` field.

• repeated Preload.Attribute attributes = 4

  Optional remaining attributes. This does not include the `href` or `as` attributes.

• bool module = 5

  If true, this is a modulepreload instead of a preload.

Used in: Preload

• string key = 1

• string val = 2

A Request encapsulates input and contextual parameters for use by the transformers.

• string html = 1

  The AMP HTML document to transform.

• string document_url = 2

  The public URL of the document, i.e. the location that should appear in the browser URL bar.

• string rtv = 4

  The AMP runtime version.

• string css = 5

  The CSS contents to inline into the transformed HTML

• repeated Request.HtmlFormat allowed_formats = 7

  Transformations are only run if the HTML tag contains the attribute specifying one of the provided formats. If allowed_formats is empty, then all non-experimental AMP formats are allowed.

• Request.TransformersConfig config = 6

• repeated string transformers = 3

  If config == CUSTOM, this is the list of custom transformers to execute, in the order provided here. Otherwise, this is ignored.

• int64 version = 8

  The version of the transforms to perform (optional). If specified, it must be a supported version.

This should be kept in sync with HtmlFormat.Code in github.com/ampproject/amphtml/validator/validator.proto. Deprecated fields, do not reuse: reserved 5;

Used in: Request

• UNKNOWN_CODE = 0

  Never used

• AMP = 1

• AMP4ADS = 2

• AMP4EMAIL = 3

• EXPERIMENTAL = 4

  Currently unused

Used in: Request

• DEFAULT = 0

  Execute the default list of transformers. For packager production environments, this should be the config used.

• NONE = 1

  Execute none, and simply parse and re-emit. Some normalization will be performed regardless, including, but not limited to: - HTML normalization (e.g. closing all non-void tags). - removal of all comments - lowercase-ing of attribute keys - lexical sort of attribute keys - text is escaped WARNING. THIS IS FOR TESTING PURPOSES ONLY. Use of this setting in a packager production environment could produce invalid transformed AMP when ingested by AMP caches.

• VALIDATION = 2

  Execute the minimum needed for verification/validation. WARNING. FOR AMP CACHE USE ONLY. Use of this setting in a packager production environment could produce invalid transformed AMP when ingested by AMP caches.

• CUSTOM = 3

  Execute a custom set of transformers. WARNING. THIS IS FOR TESTING PURPOSES ONLY. Use of this setting in a packager production environment could produce invalid transformed AMP when ingested by AMP caches.

An inclusive range of version numbers.

• int64 min = 1

• int64 max = 2