Improve error message for dependencies with no versions available (#342

)

Partially addresses #310
Addresses case at
#309 (comment)
Follow-up to #300 ensuring `PuffinExternal` is used consistently when
formatting messages

Example at
https://github.com/astral-sh/puffin/pull/342/files#diff-5c74a74ef34ef1d6e7453de8d2d19134813156e8b6a657e6b5ed71fda5a3a870

crates/puffin-cli/src/commands/pip_compile.rs

@@ -150,9 +150,8 @@ pub(crate) async fn pip_compile(
     .with_reporter(ResolverReporter::from(printer));
     let resolution = match resolver.resolve().await {
         Err(puffin_resolver::ResolveError::PubGrub(pubgrub::error::PubGrubError::NoSolution(
-            mut derivation_tree,
+            derivation_tree,
         ))) => {
-            derivation_tree.collapse_no_versions();
             #[allow(clippy::print_stderr)]
             {
                 let report =

crates/puffin-cli/tests/pip_compile.rs

@@ -1479,3 +1479,52 @@ dependencies = ["django==5.0b1", "django==5.0a1"]
 
     Ok(())
 }
+
+/// Compile requirements in a `pyproject.toml` file that cannot be resolved due to
+/// a requirement with a version that is not available online.
+#[test]
+fn compile_unsolvable_requirements_version_not_available() -> Result<()> {
+    let temp_dir = assert_fs::TempDir::new()?;
+    let cache_dir = assert_fs::TempDir::new()?;
+    let venv = temp_dir.child(".venv");
+
+    Command::new(get_cargo_bin(BIN_NAME))
+        .arg("venv")
+        .arg(venv.as_os_str())
+        .arg("--cache-dir")
+        .arg(cache_dir.path())
+        .current_dir(&temp_dir)
+        .assert()
+        .success();
+    venv.assert(predicates::path::is_dir());
+
+    let pyproject_toml = temp_dir.child("pyproject.toml");
+    pyproject_toml.touch()?;
+    pyproject_toml.write_str(
+        r#"[build-system]
+requires = ["setuptools", "wheel"]
+
+[project]
+name = "my-project"
+dependencies = ["django==300.1.4"]
+"#,
+    )?;
+
+    insta::with_settings!({
+        filters => vec![
+            (r"\d(ms|s)", "[TIME]"),
+            (r"#    .* pip-compile", "#    [BIN_PATH] pip-compile"),
+            (r"--cache-dir .*", "--cache-dir [CACHE_DIR]"),
+        ]
+    }, {
+        assert_cmd_snapshot!(Command::new(get_cargo_bin(BIN_NAME))
+            .arg("pip-compile")
+            .arg("pyproject.toml")
+            .arg("--cache-dir")
+            .arg(cache_dir.path())
+            .env("VIRTUAL_ENV", venv.as_os_str())
+            .current_dir(&temp_dir));
+    });
+
+    Ok(())
+}

crates/puffin-cli/tests/snapshots/pip_compile__compile_unsolvable_requirements_version_not_available.snap

@@ -0,0 +1,21 @@
+---
+source: crates/puffin-cli/tests/pip_compile.rs
+info:
+  program: puffin
+  args:
+    - pip-compile
+    - pyproject.toml
+    - "--cache-dir"
+    - /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmp2JLrkd
+  env:
+    VIRTUAL_ENV: /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmp0ZV4ob/.venv
+---
+success: false
+exit_code: 1
+----- stdout -----
+
+----- stderr -----
+  × No solution found when resolving dependencies:
+  ╰─▶ Because there is no version of django available matching ==300.1.4 and
+      my-project depends on django==300.1.4, my-project cannot be satisfied.
+

crates/puffin-cli/tests/snapshots/pip_compile__conflicting_direct_url_dependency.snap

@@ -6,15 +6,16 @@ info:
     - pip-compile
     - requirements.in
     - "--cache-dir"
-    - /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmpleIayX
+    - /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmpYAeXfn
   env:
-    VIRTUAL_ENV: /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmp24qRXe/.venv
+    VIRTUAL_ENV: /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmpf7hodD/.venv
 ---
 success: false
 exit_code: 1
 ----- stdout -----
 
 ----- stderr -----
   × No solution found when resolving dependencies:
-  ╰─▶ root depends on werkzeug==3.0.0
+  ╰─▶ Because there is no version of werkzeug available matching ==3.0.0 and
+      root depends on werkzeug==3.0.0, root cannot be satisfied.
 

crates/puffin-cli/tests/snapshots/pip_compile__conflicting_transitive_url_dependency.snap

@@ -6,16 +6,17 @@ info:
     - pip-compile
     - requirements.in
     - "--cache-dir"
-    - /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmpfXoEZG
+    - /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmpiccUSp
   env:
-    VIRTUAL_ENV: /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmpJkukgJ/.venv
+    VIRTUAL_ENV: /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmpCLX1o7/.venv
 ---
 success: false
 exit_code: 1
 ----- stdout -----
 
 ----- stderr -----
   × No solution found when resolving dependencies:
-  ╰─▶ Because flask ==3.0.0 depends on werkzeug >=3.0.0 and root ==0a0.dev0
-      depends on flask ==3.0.0, root ==0a0.dev0 is forbidden.
+  ╰─▶ Because there is no version of werkzeug available matching >=3.0.0 and
+      flask==3.0.0 depends on werkzeug>=3.0.0, flask ==3.0.0 is forbidden.
+      And because root depends on flask==3.0.0, root cannot be satisfied.
 

crates/puffin-resolver/src/pubgrub/report.rs

@@ -1,11 +1,9 @@
 use std::fmt;
 
-use pubgrub::package::Package;
 use pubgrub::range::Range;
 use pubgrub::report::{DerivationTree, Derived, External, Reporter};
 use pubgrub::term::Term;
 use pubgrub::type_aliases::Map;
-use pubgrub::version_set::VersionSet;
 
 use super::{PubGrubPackage, PubGrubVersion};
 
@@ -31,7 +29,7 @@ impl ResolutionFailureReporter {
         }
     }
 
-    fn build_recursive<P: Package, VS: VersionSet>(&mut self, derived: &Derived<P, VS>) {
+    fn build_recursive(&mut self, derived: &Derived<PubGrubPackage, Range<PubGrubVersion>>) {
         self.build_recursive_helper(derived);
         if let Some(id) = derived.shared_id {
             if self.shared_with_ref.get(&id).is_none() {
@@ -41,7 +39,7 @@ impl ResolutionFailureReporter {
         };
     }
 
-    fn build_recursive_helper<P: Package, VS: VersionSet>(&mut self, current: &Derived<P, VS>) {
+    fn build_recursive_helper(&mut self, current: &Derived<PubGrubPackage, Range<PubGrubVersion>>) {
         match (&*current.cause1, &*current.cause2) {
             (DerivationTree::External(external1), DerivationTree::External(external2)) => {
                 // Simplest case, we just combine two external incompatibilities.
@@ -118,11 +116,11 @@ impl ResolutionFailureReporter {
     ///
     /// The result will depend on the fact that the derived incompatibility
     /// has already been explained or not.
-    fn report_one_each<P: Package, VS: VersionSet>(
+    fn report_one_each(
         &mut self,
-        derived: &Derived<P, VS>,
-        external: &External<P, VS>,
-        current_terms: &Map<P, Term<VS>>,
+        derived: &Derived<PubGrubPackage, Range<PubGrubVersion>>,
+        external: &External<PubGrubPackage, Range<PubGrubVersion>>,
+        current_terms: &Map<PubGrubPackage, Term<Range<PubGrubVersion>>>,
     ) {
         match self.line_ref_of(derived.shared_id) {
             Some(ref_id) => self.lines.push(Self::explain_ref_and_external(
@@ -136,11 +134,11 @@ impl ResolutionFailureReporter {
     }
 
     /// Report one derived (without a line ref yet) and one external.
-    fn report_recurse_one_each<P: Package, VS: VersionSet>(
+    fn report_recurse_one_each(
         &mut self,
-        derived: &Derived<P, VS>,
-        external: &External<P, VS>,
-        current_terms: &Map<P, Term<VS>>,
+        derived: &Derived<PubGrubPackage, Range<PubGrubVersion>>,
+        external: &External<PubGrubPackage, Range<PubGrubVersion>>,
+        current_terms: &Map<PubGrubPackage, Term<Range<PubGrubVersion>>>,
     ) {
         match (&*derived.cause1, &*derived.cause2) {
             // If the derived cause has itself one external prior cause,
@@ -174,27 +172,27 @@ impl ResolutionFailureReporter {
     // String explanations #####################################################
 
     /// Simplest case, we just combine two external incompatibilities.
-    fn explain_both_external<P: Package, VS: VersionSet>(
-        external1: &External<P, VS>,
-        external2: &External<P, VS>,
-        current_terms: &Map<P, Term<VS>>,
+    fn explain_both_external(
+        external1: &External<PubGrubPackage, Range<PubGrubVersion>>,
+        external2: &External<PubGrubPackage, Range<PubGrubVersion>>,
+        current_terms: &Map<PubGrubPackage, Term<Range<PubGrubVersion>>>,
     ) -> String {
         // TODO: order should be chosen to make it more logical.
         format!(
             "Because {} and {}, {}.",
-            external1,
-            external2,
+            PuffinExternal::from_pubgrub(external1.clone()),
+            PuffinExternal::from_pubgrub(external2.clone()),
             Self::string_terms(current_terms)
         )
     }
 
     /// Both causes have already been explained so we use their refs.
-    fn explain_both_ref<P: Package, VS: VersionSet>(
+    fn explain_both_ref(
         ref_id1: usize,
-        derived1: &Derived<P, VS>,
+        derived1: &Derived<PubGrubPackage, Range<PubGrubVersion>>,
         ref_id2: usize,
-        derived2: &Derived<P, VS>,
-        current_terms: &Map<P, Term<VS>>,
+        derived2: &Derived<PubGrubPackage, Range<PubGrubVersion>>,
+        current_terms: &Map<PubGrubPackage, Term<Range<PubGrubVersion>>>,
     ) -> String {
         // TODO: order should be chosen to make it more logical.
         format!(
@@ -210,39 +208,39 @@ impl ResolutionFailureReporter {
     /// One cause is derived (already explained so one-line),
     /// the other is a one-line external cause,
     /// and finally we conclude with the current incompatibility.
-    fn explain_ref_and_external<P: Package, VS: VersionSet>(
+    fn explain_ref_and_external(
         ref_id: usize,
-        derived: &Derived<P, VS>,
-        external: &External<P, VS>,
-        current_terms: &Map<P, Term<VS>>,
+        derived: &Derived<PubGrubPackage, Range<PubGrubVersion>>,
+        external: &External<PubGrubPackage, Range<PubGrubVersion>>,
+        current_terms: &Map<PubGrubPackage, Term<Range<PubGrubVersion>>>,
     ) -> String {
         // TODO: order should be chosen to make it more logical.
         format!(
             "Because {} ({}) and {}, {}.",
             Self::string_terms(&derived.terms),
             ref_id,
-            external,
+            PuffinExternal::from_pubgrub(external.clone()),
             Self::string_terms(current_terms)
         )
     }
 
     /// Add an external cause to the chain of explanations.
-    fn and_explain_external<P: Package, VS: VersionSet>(
-        external: &External<P, VS>,
-        current_terms: &Map<P, Term<VS>>,
+    fn and_explain_external(
+        external: &External<PubGrubPackage, Range<PubGrubVersion>>,
+        current_terms: &Map<PubGrubPackage, Term<Range<PubGrubVersion>>>,
     ) -> String {
         format!(
             "And because {}, {}.",
-            external,
+            PuffinExternal::from_pubgrub(external.clone()),
             Self::string_terms(current_terms)
         )
     }
 
     /// Add an already explained incompat to the chain of explanations.
-    fn and_explain_ref<P: Package, VS: VersionSet>(
+    fn and_explain_ref(
         ref_id: usize,
-        derived: &Derived<P, VS>,
-        current_terms: &Map<P, Term<VS>>,
+        derived: &Derived<PubGrubPackage, Range<PubGrubVersion>>,
+        current_terms: &Map<PubGrubPackage, Term<Range<PubGrubVersion>>>,
     ) -> String {
         format!(
             "And because {} ({}), {}.",
@@ -253,10 +251,10 @@ impl ResolutionFailureReporter {
     }
 
     /// Add an already explained incompat to the chain of explanations.
-    fn and_explain_prior_and_external<P: Package, VS: VersionSet>(
-        prior_external: &External<P, VS>,
-        external: &External<P, VS>,
-        current_terms: &Map<P, Term<VS>>,
+    fn and_explain_prior_and_external(
+        prior_external: &External<PubGrubPackage, Range<PubGrubVersion>>,
+        external: &External<PubGrubPackage, Range<PubGrubVersion>>,
+        current_terms: &Map<PubGrubPackage, Term<Range<PubGrubVersion>>>,
     ) -> String {
         format!(
             "And because {} and {}, {}.",
@@ -267,18 +265,36 @@ impl ResolutionFailureReporter {
     }
 
     /// Try to print terms of an incompatibility in a human-readable way.
-    pub fn string_terms<P: Package, VS: VersionSet>(terms: &Map<P, Term<VS>>) -> String {
+    pub fn string_terms(terms: &Map<PubGrubPackage, Term<Range<PubGrubVersion>>>) -> String {
         let terms_vec: Vec<_> = terms.iter().collect();
         match terms_vec.as_slice() {
             [] => "version solving failed".into(),
-            // TODO: special case when that unique package is root.
-            [(package, Term::Positive(range))] => format!("{package} {range} is forbidden"),
-            [(package, Term::Negative(range))] => format!("{package} {range} is mandatory"),
+            [(package @ PubGrubPackage::Root(_), _)] => {
+                format!("{package} cannot be satisfied")
+            }
+            [(package @ PubGrubPackage::Package(..), Term::Positive(range))] => {
+                format!("{package} {range} is forbidden")
+            }
+            [(package @ PubGrubPackage::Package(..), Term::Negative(range))] => {
+                format!("{package} {range} is mandatory")
+            }
             [(p1, Term::Positive(r1)), (p2, Term::Negative(r2))] => {
-                External::FromDependencyOf(p1, r1.clone(), p2, r2.clone()).to_string()
+                PuffinExternal::FromDependencyOf(
+                    (*p1).clone(),
+                    r1.clone(),
+                    (*p2).clone(),
+                    r2.clone(),
+                )
+                .to_string()
             }
             [(p1, Term::Negative(r1)), (p2, Term::Positive(r2))] => {
-                External::FromDependencyOf(p2, r2.clone(), p1, r1.clone()).to_string()
+                PuffinExternal::FromDependencyOf(
+                    (*p2).clone(),
+                    r2.clone(),
+                    (*p1).clone(),
+                    r1.clone(),
+                )
+                .to_string()
             }
             slice => {
                 let str_terms: Vec<_> = slice.iter().map(|(p, t)| format!("{p} {t}")).collect();
@@ -366,7 +382,10 @@ impl fmt::Display for PuffinExternal {
                 if set == &Range::full() {
                     write!(f, "there is no available version for {package}")
                 } else {
-                    write!(f, "there is no version of {package} in {set}")
+                    write!(
+                        f,
+                        "there is no version of {package} available matching {set}"
+                    )
                 }
             }
             Self::UnavailableDependencies(package, set) => {