Crate iri_string

String types for RFC 3987 IRI.

Note that this crate does not have any extra knowledge about protocols. Comparisons between IRI strings by PartialEq and Eq is implemented as simple string comparison. You should implement by yourself or use another crate to use such extra knowledge to compare IRIs.

Rationale

foo:, foo:/, foo://, foo:///, foo:////, ... are valid IRIs

All of these are valid IRIs. (On the other hand, all of them are invalid as relative IRI reference, because they don't match relative-part rule, especially path-noscheme, as the first path component of the relative path contains a colon.)

• foo:
  • Decomposed to <scheme="foo">:<path-empty="">.
• foo:/
  • Decomposed to <scheme="foo">:<path-absolute="/">.
• foo://
  • Decomposed to <scheme="foo">://<authority=""><path-absolute="">.
• foo:///
  • Decomposed to <scheme="foo">://<authority=""><path-absolute="/">.
• foo:////
  • Decomposed to <scheme="foo">://<authority=""><path-absolute="//">.
• foo://///
  • Decomposed to <scheme="foo">://<authority=""><path-absolute="///">.

RFC 3986 says that "if authority is absent, path cannot start with //".

When authority is present, the path must either be empty or begin with a slash ("/") character. When authority is not present, the path cannot begin with two slash characters ("//").

--- RFC 3986, section 3. Syntax Components.

If a URI contains an authority component, then the path component must either be empty or begin with a slash ("/") character. If a URI does not contain an authority component, then the path cannot begin with two slash characters ("//").

--- RFC 3986, section 3.3. Path

We should interpret them as "if authority rule is completely unused (i.e. does not match any strings including empty string), path cannot start with //". In other words, we should consider this as explaining the ABNF of hier-part rule (especially why it does not use path rule), but not adding extra restriction to the rule written in ABNF.

This restriction is necessary to remove ambiguity in decomposition of some strings. For example, it is natural to decompose foo:// to <scheme="foo">:<path="//"> or <scheme="foo">://<authority=""><path="">. The restriction, which is already encoded to the ABNF rule, tells us to always decompose to the latter form, rather than the former one.

Readers of the spec might be confused by "when authority is present" and "if a URI contains an authority component, which is unclear. However, based on the interpretation above, we should consider authority part with empty string as satisfying the condition "authority is present".

Modules

resolve	URI and IRI resolvers.
types	URI and IRI types.
validate	Validators.