Support optional path parameters

[CathalMullan]

Optionals

Having ? at the end of a parameter name will mark it as optional.

Any characters that precede it will also be considered part of the same optional segment, excluding /.

This is less explicit than a 'grouping' syntax, but should be just as easy to understand.

Types

Dynamic Segment

/users/{id?}

Equivalent

• /users
• /users/{id}

Match

• /users -> OK
• /users/123 -> OK
• /users/123/456 -> ERR

Wildcard Segment(s)

/files/{*path?}

Equivalent

• /files
• /files/{*path}

Match

• /files -> OK
• /files/report.pdf -> OK
• /files/images/beach.jpg -> OK

Inline Dynamic Section

/users/{user}/profile.{ext?}

Equivalent

• /users/{user}/profile
• /users/{user}/profile.{ext}

Match

• /users/{user} -> ERR
• /users/{user}/profile -> OK
• /users/{user}/profile. -> ERR
• /users/{user}/profile.jpg -> OK
• /users/{user}/profile.jpg.png -> OK, BUT WEIRD

Inline Dynamic Section(s)

/release/v{major}.{minor?}.{patch?}

Equivalent

• /release/v{major}
• /release/v{major}.{minor}
• /release/v{major}.{minor}.{patch}

Match

• /release/v4 -> OK
• /release/v4. -> ERR
• /release/v4.1 -> OK
• /release/v4.1. -> ERR
• /release/v4.1.4 -> OK
• /release/v4.1.4.5 -> OK, BUT WEIRD

Parameters

All optional values will have to be returned an Option<&str>.

Constraints

Should support constraints for all types:

• /users/{id?:constraint}
• /files/{*path?:constraint}

How we decide to handle segment checks is TBD.

Limitations

Optionals MUST come at the end of a path, segment or section.

We MAY allow multiple chained optionals, undecided.

We won't support defaults in the route. Just use .unwrap_or in your framework of choice.

Prior Art

• .NET Core
• Ruby on Rails

Changes Needed

• Blocked by Reconsider router internal structure #143
• Update parser to explode '?' routes.
• Figure out how to store this in our tree.
• Figure out how to insert/delete
• Figure out how to search
• Figure out how to display