Repository: pypa/pip
File: src/pip/_internal/resolution/resolvelib/factory.py (Python)

Code before:
            logger.critical(
                "Ignored the following versions that require a different python "
                "version: %s",
                "; ".join(skipped_by_requires_python) or "none",
            )
        logger.critical(
            "Could not find a version that satisfies the requirement %s "
            "(from versions: %s)",
            req_disp,
            ", ".join(versions) or "none",
        )
        if str(req) == "requirements.txt":
            logger.info(
                "HINT: You are attempting to install a package literally "
                'named "requirements.txt" (which cannot exist). Consider '
                "using the '-r' flag to install the packages listed in "
                "requirements.txt"
            )

        return DistributionNotFound(f"No matching distribution found for {req}")

    def _has_any_candidates(self, project_name: str) -> bool:
        """
        Check if there are any candidates available for the project name.
        """
        return any(self._finder.find_all_candidates(project_name))

    def get_installation_error(
        self,
        e: ResolutionImpossible[Requirement, Candidate],
        constraints: dict[str, Constraint],
    ) -> InstallationError:
        assert e.causes, "Installation error reported with no cause"

        # If one of the things we can't solve is "we need Python X.Y",
        # that is what we report.
        requires_python_causes = [
            cause
            for cause in e.causes
            if isinstance(cause.requirement, RequiresPythonRequirement)
            and not cause.requirement.is_satisfied_by(self._python_candidate)
        ]
        if requires_python_causes:
            # The comprehension above makes sure all Requirement instances are
            # RequiresPythonRequirement, so let's cast for convenience.
            return self._report_requires_python_error(
                cast("Sequence[ConflictCause]", requires_python_causes),
            )

        # Otherwise, we have a set of causes which can't all be satisfied
        # at once.

Review comment (bug):
```suggestion
        return bool(self._finder.find_all_candidates(project_name))
```

I don't think installation candidates can ever be false, so this is a bit confusing. Alternatively, we could use `len(...) > 0` to be explicit.[^1]

[^1]: This isn't Pythonic, but honestly, I'm warming up to being more explicit as it's so easy to hide a bug with implicit boolean logic.

Code after:
            logger.critical(
                "Ignored the following versions that require a different python "
                "version: %s",
                "; ".join(skipped_by_requires_python) or "none",
            )
        logger.critical(
            "Could not find a version that satisfies the requirement %s "
            "(from versions: %s)",
            req_disp,
            ", ".join(versions) or "none",
        )
        if str(req) == "requirements.txt":
            logger.info(
                "HINT: You are attempting to install a package literally "
                'named "requirements.txt" (which cannot exist). Consider '
                "using the '-r' flag to install the packages listed in "
                "requirements.txt"
            )

        return DistributionNotFound(f"No matching distribution found for {req}")

    def _has_any_candidates(self, project_name: str) -> bool:
        """
        Check if there are any candidates available for the project name.
        """
        return any(
            self.find_candidates(
                project_name,
                requirements={project_name: []},
                incompatibilities={},
                constraint=Constraint.empty(),
                prefers_installed=True,
                is_satisfied_by=lambda r, c: True,
            )
        )

    def get_installation_error(
        self,
        e: ResolutionImpossible[Requirement, Candidate],
        constraints: dict[str, Constraint],
    ) -> InstallationError:
        assert e.causes, "Installation error reported with no cause"

        # If one of the things we can't solve is "we need Python X.Y",
        # that is what we report.
        requires_python_causes = [
            cause
            for cause in e.causes
            if isinstance(cause.requirement, RequiresPythonRequirement)
            and not cause.requirement.is_satisfied_by(self._python_candidate)
        ]