Improve error messages for incompatible direct requirements

crates/puffin-cli/tests/pip_compile.rs

@@ -1432,9 +1432,10 @@ optional-dependencies.bar = [
     Ok(())
 }
 
-/// Compile requirements that cannot be solved due to conflict in a `pyproject.toml` fil;e.
+/// Compile requirements that cannot be solved due to conflict in a `pyproject.toml` file
+/// where two direct requirements of a package have incompatible pinned versions.
 #[test]
-fn compile_unsolvable_requirements() -> Result<()> {
+fn compile_unsolvable_requirements_direct_pinned() -> Result<()> {
     let temp_dir = assert_fs::TempDir::new()?;
     let cache_dir = assert_fs::TempDir::new()?;
     let venv = temp_dir.child(".venv");
@@ -1462,11 +1463,142 @@ dependencies = ["django==5.0b1", "django==5.0a1"]
     )?;
 
     insta::with_settings!({
-        filters => vec![
-            (r"\d(ms|s)", "[TIME]"),
-            (r"#    .* pip-compile", "#    [BIN_PATH] pip-compile"),
-            (r"--cache-dir .*", "--cache-dir [CACHE_DIR]"),
-        ]
+        filters => INSTA_FILTERS.to_vec()
+    }, {
+        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(())
+}
+
+/// Compile requirements that cannot be solved due to conflict in a `pyproject.toml` file
+/// where two direct requirements of a package have incompatible version ranges.
+#[test]
+fn compile_unsolvable_requirements_direct_ranges() -> 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>=4.0", "django<=3.0"]
+"#,
+    )?;
+
+    insta::with_settings!({
+        filters => INSTA_FILTERS.to_vec()
+    }, {
+        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(())
+}
+
+/// Compile requirements that cannot be solved due to conflict in a `pyproject.toml` file
+/// where direct requirements of a package have a mix of compatible and incompatible version ranges.
+#[test]
+fn compile_unsolvable_requirements_direct_mixed_ranges() -> 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>=3.0", "django<=3.0", "django>5.0"]
+"#,
+    )?;
+
+    insta::with_settings!({
+        filters => INSTA_FILTERS.to_vec()
+    }, {
+        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(())
+}
+
+/// Compile requirements in a `pyproject.toml` file where there are multiple direct requirements of a package
+/// but the versions are compatible.
+#[test]
+fn compile_solvable_requirements_multiple_direct_versions_for_package() -> 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>=3.0", "django<=3.0", "django==3.0"]
+"#,
+    )?;
+
+    insta::with_settings!({
+        filters => INSTA_FILTERS.to_vec()
     }, {
         assert_cmd_snapshot!(Command::new(get_cargo_bin(BIN_NAME))
             .arg("pip-compile")

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

@@ -0,0 +1,28 @@
+---
+source: crates/puffin-cli/tests/pip_compile.rs
+info:
+  program: puffin
+  args:
+    - pip-compile
+    - pyproject.toml
+    - "--cache-dir"
+    - /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmpcfI6sl
+  env:
+    VIRTUAL_ENV: /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmpv4PQoW/.venv
+---
+success: true
+exit_code: 0
+----- stdout -----
+# This file was autogenerated by Puffin v0.0.1 via the following command:
+#    [BIN_PATH] pip-compile pyproject.toml --cache-dir [CACHE_DIR]
+asgiref==3.7.2
+    # via django
+django==3.0
+pytz==2023.3.post1
+    # via django
+sqlparse==0.4.4
+    # via django
+
+----- stderr -----
+Resolved 4 packages in [TIME]
+

crates/puffin-cli/tests/snapshots/pip_compile__compile_unsolvable_requirements.snap → crates/puffin-cli/tests/snapshots/pip_compile__compile_unsolvable_requirements_direct_ranges.snap

@@ -6,15 +6,14 @@ info:
     - pip-compile
     - pyproject.toml
     - "--cache-dir"
-    - /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmpN531dN
+    - /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmpAFfkaN
   env:
-    VIRTUAL_ENV: /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmp99w9dK/.venv
+    VIRTUAL_ENV: /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmpOGc5nS/.venv
 ---
 success: false
-exit_code: 1
+exit_code: 2
 ----- stdout -----
 
 ----- stderr -----
-  × No solution found when resolving dependencies:
-  ╰─▶ my-project depends on django∅
+error: Conflicting versions requested for package `django`: `>=4.0` is incompatible with `<=3.0`
 

crates/puffin-resolver/src/error.rs

@@ -39,6 +39,9 @@ pub enum ResolveError {
     #[error("Conflicting URLs for package `{0}`: {1} and {2}")]
     ConflictingUrls(PackageName, String, String),
 
+    #[error("Conflicting versions requested for package `{0}`: `{1}` is incompatible with `{2}`")]
+    ConflictingPackageVersions(PackageName, Range<PubGrubVersion>, Range<PubGrubVersion>),
+
     #[error("Package `{0}` attempted to resolve via URL: {1}. URL dependencies must be expressed as direct requirements or constraints. Consider adding `{0} @ {1}` to your dependencies or constraints file.")]
     DisallowedUrl(PackageName, Url),
 

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

@@ -59,7 +59,7 @@ impl PubGrubDependencies {
 
                 if let Some(entry) = dependencies.get_key_value(&package) {
                     // Merge the versions.
-                    let version = merge_versions(entry.1, &version);
+                    let version = merge_versions(&requirement.name, entry.1, &version)?;
 
                     // Merge the package.
                     if let Some(package) = merge_package(entry.0, &package)? {
@@ -107,7 +107,7 @@ impl PubGrubDependencies {
 
                 if let Some(entry) = dependencies.get_key_value(&package) {
                     // Merge the versions.
-                    let version = merge_versions(entry.1, &version);
+                    let version = merge_versions(&constraint.name, entry.1, &version)?;
 
                     // Merge the package.
                     if let Some(package) = merge_package(entry.0, &package)? {
@@ -178,10 +178,21 @@ fn to_pubgrub(
 
 /// Merge two [`PubGrubVersion`] ranges.
 fn merge_versions(
+    package_name: &PackageName,
     left: &Range<PubGrubVersion>,
     right: &Range<PubGrubVersion>,
-) -> Range<PubGrubVersion> {
-    left.intersection(right)
+) -> Result<Range<PubGrubVersion>, ResolveError> {
+    let version = left.intersection(right);
+
+    if version.is_empty() {
+        Err(ResolveError::ConflictingPackageVersions(
+            package_name.clone(),
+            left.clone(),
+            right.clone(),
+        ))
+    } else {
+        Ok(version)
+    }
 }
 
 /// Merge two [`PubGrubPackage`] instances.

vendor/pubgrub/src/range.rs

@@ -117,6 +117,10 @@ impl<V> Range<V> {
             segments: SmallVec::one((Included(v1.into()), Excluded(v2.into()))),
         }
     }
+
+    pub fn is_empty(&self) -> bool {
+        return self.segments.is_empty();
+    }
 }
 
 impl<V: Clone> Range<V> {