Add canonical interface name

Author: lann

design/mvp/Binary.md

@@ -371,10 +371,13 @@ flags are set.
 (See [Import and Export Definitions](Explainer.md#import-and-export-definitions)
 in the explainer.)
 ```ebnf
-import      ::= in:<importname'> ed:<externdesc>                     => (import in ed)
-export      ::= en:<exportname'> si:<sortidx> ed?:<externdesc>?      => (export en si ed?)
-importname' ::= 0x00 len:<u32> in:<importname>                       => in  (if len = |in|)
-exportname' ::= 0x00 len:<u32> en:<exportname>                       => en  (if len = |en|)
+import         ::= in:<importname'> ed:<externdesc>                     => (import in ed)
+export         ::= en:<exportname'> si:<sortidx> ed?:<externdesc>?      => (export en si ed?)
+importname'    ::= 0x00 len:<u32> in:<importname>                       => in     (if len = |in|)
+                 | 0x01 len:<u32> in:<importname> vs:<versionsuffix'>   => in vs  (if len = |in|)
+exportname'    ::= 0x00 len:<u32> en:<exportname>                       => en     (if len = |en|)
+                 | 0x01 len:<u32> en:<exportname> vs:<versionsuffix'>   => in vs  (if len = |in|)
+versionsuffix' ::= len:<u32> vs:<semversuffix>                          => (versionsuffix vs)  (if len = |vs|)
 ```
 
 Notes:
@@ -399,7 +402,11 @@ Notes:
   `(result (own $R))`, where `$R` is the resource labeled `r`.
 * Validation of `[method]` names requires the first parameter of the function
   to be `(param "self" (borrow $R))`, where `$R` is the resource labeled `r`.
-* `<valid semver>` is as defined by [https://semver.org](https://semver.org/)
+* Validation requires that `versionsuffix` is preceded by an `interfaceversion`
+  matching `canonversion` and that the concatenation of the `canonversion` and
+  the `versionsuffix` results in a `valid semver` as defined by
+  [https://semver.org](https://semver.org/). A `versionsuffix` is otherwise
+  ignored for validation except to improve diagnostic messages.
 * `<integrity-metadata>` is as defined by the
   [SRI](https://www.w3.org/TR/SRI/#dfn-integrity-metadata) spec.
 
@@ -494,7 +501,9 @@ named once.
 
 * The opcodes (for types, canon built-ins, etc) should be re-sorted
 * The two `list` type codes should be merged into one with an optional immediate.
-* The `0x00` prefix byte of `importname'` and `exportname'` will be removed or repurposed.
+* The `0x00` variant of `importname'` and `exportname'` will be removed. Any
+  remaining variant(s) will be renumbered or the prefix byte will be removed or
+  repurposed.
 
 
 [`core:byte`]: https://webassembly.github.io/spec/core/binary/values.html#binary-byte

design/mvp/Explainer.md

@@ -33,6 +33,7 @@ more user-focused explanation, take a look at the
   * [Start definitions](#-start-definitions)
   * [Import and export definitions](#import-and-export-definitions)
     * [Name uniqueness](#name-uniqueness)
+    * [Canonical interface name](#canonical-interface-name)
 * [Component invariants](#component-invariants)
 * [JavaScript embedding](#JavaScript-embedding)
   * [JS API](#JS-API)
@@ -294,7 +295,7 @@ sort           ::= core <core:sort>
                  | type
                  | component
                  | instance
-inlineexport   ::= (export <exportname> <sortidx>)
+inlineexport   ::= (export "<exportname>" <versionsuffix>? <sortidx>)
 ```
 Because component-level function, type and instance definitions are different
 than core-level function, type and instance definitions, they are put into
@@ -574,8 +575,8 @@ instancedecl  ::= core-prefix(<core:type>)
                 | <alias>
                 | <exportdecl>
                 | <value> 🪙
-importdecl    ::= (import <importname> bind-id(<externdesc>))
-exportdecl    ::= (export <exportname> bind-id(<externdesc>))
+importdecl    ::= (import "<importname>" <versionsuffix>? bind-id(<externdesc>))
+exportdecl    ::= (export "<exportname>" <versionsuffix>? bind-id(<externdesc>))
 externdesc    ::= (<sort> (type <u32>) )
                 | core-prefix(<core:moduletype>)
                 | <functype>
@@ -988,6 +989,10 @@ and `$C1` is a subtype of `$C2`:
 )
 ```
 
+Note that [canonical interface names](#canonical-interface-name) may be
+annotated with a `versionsuffix` which is ignored for type checking except to
+improve diagnostic messages.
+
 When we next consider type imports and exports, there are two distinct
 subcases of `typebound` to consider: `eq` and `sub`.
 
@@ -2242,8 +2247,9 @@ the identifier `$x`). In the case of exports, the `<id>?` right after the
 preceding definition being exported (e.g., `(export $x "x" (func $f))` binds a
 new identifier `$x`).
 ```ebnf
-import ::= (import "<importname>" bind-id(<externdesc>))
-export ::= (export <id>? "<exportname>" <sortidx> <externdesc>?)
+import        ::= (import "<importname>" <versionsuffix>? bind-id(<externdesc>))
+export        ::= (export <id>? "<exportname>" <versionsuffix>? <sortidx> <externdesc>?)
+versionsuffix ::= (versionsuffix "<semversuffix>")
 ```
 All import names are required to be [strongly-unique]. Separately, all export
 names are also required to be [strongly-unique]. The rest of the grammar for
@@ -2276,17 +2282,24 @@ fragment      ::= <word>
                 | <acronym>
 word          ::= [a-z] [0-9a-z]*
 acronym       ::= [A-Z] [0-9A-Z]*
-interfacename ::= <namespace> <label> <projection> <version>?
-                | <namespace>+ <label> <projection>+ <version>? 🪺
+interfacename ::= <namespace> <label> <projection> <interfaceversion>?
+                | <namespace>+ <label> <projection>+ <interfaceversion>? 🪺
 namespace     ::= <words> ':'
 words         ::= <word>
                 | <words> '-' <word>
 projection    ::= '/' <label>
-version       ::= '@' <valid semver>
+# FIXME: surrounding alignment
+interfaceversion  ::= '@' <valid semver>
+                    | '@' <canonversion>
+canonversion      ::= [1-9] [0-9]*
+                    | '0.' [1-9] [0-9]*
+                    | '0.0.' [1-9] [0-9]*
+semversuffix      ::= [0-9A-Za-z.+-]*
 depname       ::= 'unlocked-dep=<' <pkgnamequery> '>'
                 | 'locked-dep=<' <pkgname> '>' ( ',' <hashname> )?
 pkgnamequery  ::= <pkgpath> <verrange>?
-pkgname       ::= <pkgpath> <version>?
+pkgname       ::= <pkgpath> <pkgversion>?
+pkgversion    ::= '@' <valid semver>
 pkgpath       ::= <namespace> <words>
                 | <namespace>+ <words> <projection>* 🪺
 verrange      ::= '@*'
@@ -2372,12 +2385,14 @@ tooling as "registries":
   parameter of [`WebAssembly.instantiate()`])
 
 The `valid semver` production is as defined by the [Semantic Versioning 2.0]
-spec and is meant to be interpreted according to that specification. The
-`verrange` production embeds a minimal subset of the syntax for version ranges
-found in common package managers like `npm` and `cargo` and is meant to be
-interpreted with the same [semantics][SemVerRange]. (Mostly this
-interpretation is the usual SemVer-spec-defined ordering, but note the
-particular behavior of pre-release tags.)
+spec and is meant to be interpreted according to that specification. The use of
+`valid semver` in `interfaceversion` is temporary for backward compatibility;
+see [Canonical interface name](#canonical-interface-name) below. The `verrange`
+production embeds a minimal subset of the syntax for version ranges found in
+common package managers like `npm` and `cargo` and is meant to be interpreted
+with the same [semantics][SemVerRange]. (Mostly this interpretation is the usual
+SemVer-spec-defined ordering, but note the particular behavior of pre-release
+tags.)
 
 The `plainname` production captures several language-neutral syntactic hints
 that allow bindings generators to produce more idiomatic bindings in their
@@ -2539,6 +2554,53 @@ annotations. For example, the validation rules for `[constructor]foo` require
 for details.
 
 
+### Canonical Interface Name
+
+An `interfacename` (as defined above) is **canonical** iff it either:
+
+- has no `interfaceversion`
+- has an `interfaceversion` matching the `canonversion` production
+
+The purpose of `canonversion` is to simplify the matching of compatible import
+and export versions. For example, if a guest imports some interface from
+`wasi:http/[email protected]` and a host provides the (subtype-compatible) interface
+`wasi:http/[email protected]`, we'd like to make it easy for the host to link with the
+guest. The `canonversion` for both of these interfaces would be `0.2`, so this
+linking could be done by matching canonical interface names literally.
+Symmetrically, if a host provides `wasi:http/[email protected]` and a guest imports
+`wasi:http/[email protected]`, so long as the guest only uses the subset of
+functions defined in `wasi:http/[email protected]` (which is checked by normal
+component type validation), linking succeeds. Thus, including only the
+canonicalized version in the name allows both backwards and (limited)
+forwards compatibility using only trivial string equality (as well as the
+type checking already required).
+
+Any `valid semver` (as used in WIT) can be canonicalized by splitting it into
+two parts - the `canonversion` prefix and the remaining `semversuffix`. Using
+the `<major>.<minor>.<patch>` syntax of [Semantic Versioning 2.0], the split
+point is chosen as follows:
+
+- if `major` > 0, split immediately after `major`
+  - `1.2.3` &rarr; `1` / `.2.3`
+- otherwise if `minor` > 0, split immediately after `minor`
+  - `0.2.6-rc.1` &rarr; `0.2` / `.6-rc.1`
+- otherwise, split immediately after `patch`
+  - `0.0.1-alpha` &rarr; `0.0.1` / `-alpha`
+
+When a version is canonicalized, any `semversuffix` that was split off of the
+version should be preserved in the `versionsuffix` field of any resulting
+`import`s and `export`s. This gives component runtimes and other tools access to
+the original version for error messages, documentation, and other development
+purposes. Where a `versionsuffix` is present the preceding `interfacename` must
+have a `canonversion`, and the concatenation of the `canonversion` and
+`versionsuffix` must be a `valid semver`.
+
+For compatibility with older versions of this spec, non-canonical
+`interfacename`s (with `interfaceversion`s matching any `valid semver`) are
+temporarily permitted. These non-canonical names may trigger warnings and will
+start being rejected some time after after [WASI Preview 3] is released.
+
+
 ## Component Invariants
 
 As a consequence of the shared-nothing design described above, all calls into
@@ -2894,6 +2956,7 @@ For some use-case-focused, worked examples, see:
 [`rectype`]: https://webassembly.github.io/gc/core/text/types.html#text-rectype
 [shared-everything-threads]: https://github.com/WebAssembly/shared-everything-threads
 [WASI Preview 2]: https://github.com/WebAssembly/WASI/tree/main/wasip2#readme
+[WASI Preview 3]: https://github.com/WebAssembly/WASI/tree/main/wasip2#looking-forward-to-preview-3
 [reference types]: https://github.com/WebAssembly/reference-types/blob/master/proposals/reference-types/Overview.md
 
 [Strongly-unique]: #name-uniqueness