[guppy] add support for postfilters

Use it in `cargo-guppy` to implement filtering for
third-party deps.

cargo-guppy/src/core.rs

@@ -5,6 +5,7 @@
 
 use anyhow::{anyhow, ensure};
 use clap::arg_enum;
+use guppy::graph::cargo::{CargoPostfilter, CargoResolvePhase};
 use guppy::graph::{
     DependencyDirection, DependencyReq, EnabledTernary, PackageGraph, PackageLink, PackageQuery,
 };
@@ -13,7 +14,7 @@ use std::collections::HashSet;
 use structopt::StructOpt;
 
 arg_enum! {
-    #[derive(Debug)]
+    #[derive(Copy, Clone, Debug)]
     pub enum Kind {
         All,
         Workspace,
@@ -22,6 +23,25 @@ arg_enum! {
     }
 }
 
+impl Kind {
+    /// Returns true if this link should be traversed.
+    pub fn should_traverse(self, link: &PackageLink<'_>) -> bool {
+        // NOTE: We always retain all workspace deps in the graph, otherwise
+        // we'll get a disconnected graph.
+        match self {
+            Kind::All | Kind::ThirdParty => true,
+            Kind::DirectThirdParty => link.from().in_workspace(),
+            Kind::Workspace => link.from().in_workspace() && link.to().in_workspace(),
+        }
+    }
+}
+
+impl<'g> CargoPostfilter<'g> for Kind {
+    fn accept_package(&mut self, _phase: CargoResolvePhase<'_, '_>, link: PackageLink<'_>) -> bool {
+        self.should_traverse(&link)
+    }
+}
+
 #[derive(Debug, StructOpt)]
 pub struct QueryOptions {
     /// Query reverse transitive dependencies (default: forward)
@@ -67,6 +87,10 @@ pub struct BaseFilterOptions {
     /// Omit edges that point into a given package; useful for seeing how
     /// removing a dependency affects the graph
     pub omit_edges_into: Vec<String>,
+
+    #[structopt(long, short, possible_values = &Kind::variants(), case_insensitive = true, default_value = "all")]
+    /// Kind of crates to select
+    pub kind: Kind,
 }
 
 impl BaseFilterOptions {
@@ -85,10 +109,6 @@ pub struct FilterOptions {
     #[structopt(flatten)]
     pub base_opts: BaseFilterOptions,
 
-    #[structopt(long, short, possible_values = &Kind::variants(), case_insensitive = true, default_value = "all")]
-    /// Kind of crates to select
-    pub kind: Kind,
-
     #[structopt(long, rename_all = "kebab-case")]
     /// Include dev dependencies
     pub include_dev: bool,
@@ -119,15 +139,8 @@ impl FilterOptions {
         };
 
         move |_, link| {
-            let (from, to) = link.endpoints();
             // filter by the kind of dependency (--kind)
-            // NOTE: We always retain all workspace deps in the graph, otherwise
-            // we'll get a disconnected graph.
-            let include_kind = match self.kind {
-                Kind::All | Kind::ThirdParty => true,
-                Kind::DirectThirdParty => from.in_workspace(),
-                Kind::Workspace => from.in_workspace() && to.in_workspace(),
-            };
+            let include_kind = self.base_opts.kind.should_traverse(&link);
 
             let include_type = if let Some(platform) = &platform {
                 // filter out irrelevant dependencies for a specific target (--target)
@@ -140,7 +153,7 @@ impl FilterOptions {
             };
 
             // filter out provided edge targets (--omit-edges-into)
-            let include_edge = !omitted_package_ids.contains(to.id());
+            let include_edge = !omitted_package_ids.contains(link.to().id());
 
             include_kind && include_type && include_edge
         }

cargo-guppy/src/lib.rs

@@ -123,8 +123,9 @@ pub fn cmd_resolve_cargo(opts: &ResolveCargoOptions) -> Result<(), anyhow::Error
     let host_platform = triple_to_platform(opts.host_platform.as_deref(), || None)?;
     let mut command = opts.metadata_opts.make_command();
     let pkg_graph = command.build_graph()?;
+    let mut kind_postfilter = opts.base_filter_opts.kind;
 
-    let cargo_opts = CargoOptions::new()
+    let mut cargo_opts = CargoOptions::new_postfilter(&mut kind_postfilter)
         .with_dev_deps(opts.include_dev)
         .with_target_platform(target_platform.as_ref())
         .with_host_platform(host_platform.as_ref())
@@ -133,19 +134,25 @@ pub fn cmd_resolve_cargo(opts: &ResolveCargoOptions) -> Result<(), anyhow::Error
     let cargo_set = opts
         .pf
         .make_feature_query(&pkg_graph)?
-        .resolve_cargo(&cargo_opts)?;
+        .resolve_cargo(&mut cargo_opts)?;
 
-    fn print_packages(feature_set: &FeatureSet) {
+    let print_packages = |feature_set: &FeatureSet| {
         for feature_list in feature_set.packages_with_features(DependencyDirection::Forward) {
             let package = feature_list.package();
-            println!(
-                "{} {}: {}",
-                package.name(),
-                package.version(),
-                feature_list.display_features()
-            );
+            let show_package = match opts.base_filter_opts.kind {
+                Kind::All | Kind::Workspace => true,
+                Kind::DirectThirdParty | Kind::ThirdParty => !package.in_workspace(),
+            };
+            if show_package {
+                println!(
+                    "{} {}: {}",
+                    package.name(),
+                    package.version(),
+                    feature_list.display_features()
+                );
+            }
         }
-    }
+    };
 
     match opts.build_kind {
         BuildKind::All => {
@@ -204,7 +211,7 @@ pub fn cmd_select(options: &CmdSelectOptions) -> Result<(), anyhow::Error> {
         let direct_dep = package
             .reverse_direct_links()
             .any(|link| link.from().in_workspace() && !link.to().in_workspace());
-        let show_package = match options.filter_opts.kind {
+        let show_package = match options.filter_opts.base_opts.kind {
             Kind::All => true,
             Kind::Workspace => in_workspace,
             Kind::DirectThirdParty => direct_dep,