SERVER-35121 added verification of python requirements.txt.

1 files changed, 73 insertions, 0 deletions

diff --git a/site_scons/mongo/pip_requirements.py b/site_scons/mongo/pip_requirements.py
new file mode 100644
index 00000000000..5fd9b947b02
--- /dev/null
+++ b/site_scons/mongo/pip_requirements.py
@@ -0,0 +1,73 @@
+# -*- mode: python; -*-
+
+# Try to keep this modules imports minimum and only
+# import python standard modules, because this module
+# should be used for finding such external modules or
+# missing dependencies.
+import sys
+
+
+class MissingRequirements(Exception):
+    """Raised when when verify_requirements() detects missing requirements."""
+    pass
+
+
+def verify_requirements(requirements_file: str, silent: bool = False):
+    """Check if the modules in a pip requirements file are installed.
+    This allows for a more friendly user message with guidance on how to
+    resolve the missing dependencies.
+    Args:
+        requirements_file: path to a pip requirements file.
+        silent: True if the function should print.
+    Raises:
+        MissingRequirements if any requirements are missing
+    """
+
+    def verbose(*args, **kwargs):
+        if not silent:
+            print(*args, **kwargs)
+
+    def raiseSuggestion(ex, pip_pkg):
+        raise MissingRequirements(
+            f"{ex}\n"
+            f"Try running:\n"
+            f"    {sys.executable} -m pip install {pip_pkg}"
+        ) from ex
+
+    # Import the prequisites for this function, providing hints on failure.
+    try:
+        import requirements
+    except ModuleNotFoundError as ex:
+        raiseSuggestion(ex, "requirements_parser")
+
+    try:
+        import pkg_resources
+    except ModuleNotFoundError as ex:
+        raiseSuggestion(ex, "setuptools")
+
+    verbose("Checking required python packages...")
+
+    # Reduce a pip requirements file to its PEP 508 requirement specifiers.
+    with open(requirements_file) as fd:
+        pip_lines = [p.line for p in requirements.parse(fd)]
+
+    # The PEP 508 requirement specifiers can be parsed by the `pkg_resources`.
+    pkg_requirements = list(pkg_resources.parse_requirements(pip_lines))
+
+    verbose("Requirements list:")
+    for req in sorted(set([str(req) for req in pkg_requirements])):
+        verbose(f"    {req}")
+
+    # Resolve all the requirements at once.
+    # This should help expose dependency hell among the requirements.
+    try:
+        dists = pkg_resources.working_set.resolve(pkg_requirements)
+    except pkg_resources.ResolutionError as ex:
+        raiseSuggestion(
+            ex,
+            f"-r {requirements_file}")
+
+
+    verbose("Resolved to these distributions:")
+    for dist in sorted(set([f"    {dist.key} {dist.version}" for dist in dists])):
+        verbose(dist)