11use std:: borrow:: Borrow ;
2+ use std:: cmp;
23use std:: collections:: { HashMap , HashSet } ;
34use std:: fmt;
45use std:: iter:: FromIterator ;
@@ -15,7 +16,6 @@ use super::encode::Metadata;
1516///
1617/// Each instance of `Resolve` also understands the full set of features used
1718/// for each package.
18- #[ derive( PartialEq ) ]
1919pub struct Resolve {
2020 /// A graph, whose vertices are packages and edges are dependency specifications
2121/// from `Cargo.toml`. We need a `Vec` here because the same package
@@ -59,9 +59,12 @@ pub struct Resolve {
5959///
6060/// It's theorized that we can add more here over time to track larger changes
6161/// to the `Cargo.lock` format, but we've yet to see how that strategy pans out.
62- #[ derive( PartialEq , Clone , Debug ) ]
62+ #[ derive( PartialEq , Eq , Clone , Copy , Debug , PartialOrd , Ord ) ]
6363pub enum ResolveVersion {
64+ // Historical baseline for when this abstraction was added.
6465 V1 ,
66+ // Update around 2019 where `dependencies` arrays got compressed and
67+ // checksums are listed inline.
6568 V2 ,
6669}
6770
@@ -210,21 +213,35 @@ unable to verify that `{0}` is the same as when the lockfile was generated
210213 // Be sure to just copy over any unknown metadata.
211214 self . metadata = previous. metadata . clone ( ) ;
212215
213- // The goal of Cargo is largely to preserve the encoding of
214- // `Cargo.lock` that it finds on the filesystem. Sometimes `Cargo.lock`
215- // changes are in the works where they haven't been set as the default
216- // yet but will become the default soon. We want to preserve those
217- // features if we find them.
216+ // The goal of Cargo is largely to preserve the encoding of `Cargo.lock`
217+ // that it finds on the filesystem. Sometimes `Cargo.lock` changes are
218+ // in the works where they haven't been set as the default yet but will
219+ // become the default soon.
218220 //
219- // For this reason if the previous `Cargo.lock` is from the future, or
220- // otherwise it looks like it's produced with future features we
221- // understand, then the new resolve will be encoded with the same
222- // version. Note that new instances of `Resolve` always use the default
223- // encoding, and this is where we switch it to a future encoding if the
224- // future encoding isn't yet the default.
225- if previous. version . from_the_future ( ) {
226- self . version = previous. version . clone ( ) ;
227- }
221+ // The scenarios we could be in are:
222+ //
223+ // * This is a brand new lock file with nothing previous. In that case
224+ // this method isn't actually called at all, but instead
225+ // `default_for_new_lockfiles` called below was encoded during the
226+ // resolution step, so that's what we're gonna use.
227+ //
228+ // * We have an old lock file. In this case we want to switch the
229+ // version to `default_for_old_lockfiles`. That puts us in one of
230+ // three cases:
231+ //
232+ // * Our version is older than the default. This means that we're
233+ // migrating someone forward, so we switch the encoding.
234+ // * Our version is equal to the default, nothing to do!
235+ // * Our version is *newer* than the default. This is where we
236+ // critically keep the new version of encoding.
237+ //
238+ // This strategy should get new lockfiles into the pipeline more quickly
239+ // while ensuring that any time an old cargo sees a future lock file it
240+ // keeps the future lockfile encoding.
241+ self . version = cmp:: max (
242+ previous. version ,
243+ ResolveVersion :: default_for_old_lockfiles ( ) ,
244+ ) ;
228245
229246 Ok ( ( ) )
230247 }
@@ -358,6 +375,26 @@ unable to verify that `{0}` is the same as when the lockfile was generated
358375 }
359376}
360377
378+ impl PartialEq for Resolve {
379+ fn eq ( & self , other : & Resolve ) -> bool {
380+ macro_rules! compare {
381+ ( $( $fields: ident) * | $( $ignored: ident) * ) => {
382+ let Resolve { $( $fields, ) * $( $ignored, ) * } = self ;
383+ $( drop( $ignored) ; ) *
384+ $( $fields == & other. $fields) &&*
385+ }
386+ }
387+ compare ! {
388+ // fields to compare
389+ graph replacements reverse_replacements empty_features features
390+ checksums metadata unused_patches public_dependencies
391+ |
392+ // fields to ignore
393+ version
394+ }
395+ }
396+ }
397+
361398impl fmt:: Debug for Resolve {
362399 fn fmt ( & self , fmt : & mut fmt:: Formatter < ' _ > ) -> fmt:: Result {
363400 writeln ! ( fmt, "graph: {:?}" , self . graph) ?;
@@ -370,23 +407,26 @@ impl fmt::Debug for Resolve {
370407}
371408
372409impl ResolveVersion {
373- /// The default way to encode `Cargo.lock`.
410+ /// The default way to encode new `Cargo.lock` files .
374411///
375- /// This is used for new `Cargo.lock` files that are generated without a
376- /// previous `Cargo.lock` files, and generally matches with what we want to
377- /// encode.
378- pub fn default ( ) -> ResolveVersion {
379- ResolveVersion :: V1
412+ /// It's important that if a new version of `ResolveVersion` is added that
413+ /// this is not updated until *at least* the support for the version is in
414+ /// the stable release of Rust. It's ok for this to be newer than
415+ /// `default_for_old_lockfiles` below.
416+ pub fn default_for_new_lockfiles ( ) -> ResolveVersion {
417+ ResolveVersion :: V2
380418 }
381419
382- /// Returns whether this encoding version is "from the future".
420+ /// The default way to encode old preexisting `Cargo.lock` files. This is
421+ /// often trailing the new lockfiles one above to give older projects a
422+ /// longer time to catch up.
383423///
384- /// This means that this encoding version is not currently the default but
385- /// intended to become the default "soon".
386- pub fn from_the_future ( & self ) -> bool {
387- match self {
388- ResolveVersion :: V2 => true ,
389- ResolveVersion :: V1 => false ,
390- }
424+ /// It's important that this trails behind `default_for_new_lockfiles` for
425+ /// quite some time. This gives projects a quite large window to update in
426+ /// where we don't force updates, so if projects span many versions of Cargo
427+ /// all those versions of Cargo will have support for a new version of the
428+ /// lock file.
429+ pub fn default_for_old_lockfiles ( ) -> ResolveVersion {
430+ ResolveVersion :: V1
391431 }
392432}
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