Drop run-time version constraints for modern Pip

Modern Pip (v9.0.0+) supports `Requires-Python` and so automatically
takes the current Python version into account, when determining the
latest version of packages that can be installed.

As such, for modern Pip we don't need to specify version range
constraints for the pip/setuptools/wheel versions passed to the
`pip install` at `get-pip.py` run-time.

This is the first step towards being able to remove `SCRIPT_CONSTRAINTS`
and rely purely on `Requires-Python` metadata, per:
#88 (comment)

I've intentionally left the "figure out what Pip version to embed in the
template" part of template generation alone for now to keep the PR
smaller, and have only changed the run-time `pip install` parts.

I had to add a new `pre-9.py` template file (created as a copy of
`pre-10.py`), since it's only pip<9 that needs the various version
constraint references in the template (and otherwise anything else that
used `pre-10.py`, such as Python 2.6, would have had redundant version
constraints). The new `pre-9.py` template is only used for Python 3.2.

public/2.6/get-pip.py

@@ -147,11 +147,11 @@ def parse_args(self, args):
 
     # Add any implicit installations to the end of our args
     if implicit_pip:
-        args += ["pip<10"]
+        args += ["pip"]
     if implicit_setuptools:
-        args += ["setuptools<37"]
+        args += ["setuptools"]
     if implicit_wheel:
-        args += ["wheel<0.30"]
+        args += ["wheel"]
 
     delete_tmpdir = False
     try:

public/2.7/get-pip.py

@@ -149,9 +149,9 @@ def cert_parse_args(self, args):
 
     # Add any implicit installations to the end of our args
     if implicit_pip:
-        args += ["pip<21.0"]
+        args += ["pip"]
     if implicit_setuptools:
-        args += ["setuptools<45"]
+        args += ["setuptools"]
     if implicit_wheel:
         args += ["wheel"]
 

public/3.3/get-pip.py

@@ -147,11 +147,11 @@ def parse_args(self, args):
 
     # Add any implicit installations to the end of our args
     if implicit_pip:
-        args += ["pip<18"]
+        args += ["pip"]
     if implicit_setuptools:
         args += ["setuptools"]
     if implicit_wheel:
-        args += ["wheel<0.30"]
+        args += ["wheel"]
 
     # Add our default arguments
     args = ["install", "--upgrade", "--force-reinstall"] + args

public/3.4/get-pip.py

@@ -147,7 +147,7 @@ def parse_args(self, args):
 
     # Add any implicit installations to the end of our args
     if implicit_pip:
-        args += ["pip<19.2"]
+        args += ["pip"]
     if implicit_setuptools:
         args += ["setuptools"]
     if implicit_wheel:

public/3.5/get-pip.py

@@ -149,7 +149,7 @@ def cert_parse_args(self, args):
 
     # Add any implicit installations to the end of our args
     if implicit_pip:
-        args += ["pip<21.0"]
+        args += ["pip"]
     if implicit_setuptools:
         args += ["setuptools"]
     if implicit_wheel:

public/3.6/get-pip.py

@@ -69,7 +69,7 @@ def determine_pip_install_arguments():
     pre_parser.add_argument("--no-wheel", action="store_true")
     pre, args = pre_parser.parse_known_args()
 
-    args.append("pip<22.0")
+    args.append("pip")
 
     if include_setuptools(pre):
         args.append("setuptools")

public/3.7/get-pip.py

@@ -69,7 +69,7 @@ def determine_pip_install_arguments():
     pre_parser.add_argument("--no-wheel", action="store_true")
     pre, args = pre_parser.parse_known_args()
 
-    args.append("pip<24.1")
+    args.append("pip")
 
     if include_setuptools(pre):
         args.append("setuptools")

scripts/generate.py

@@ -23,48 +23,34 @@
 SCRIPT_CONSTRAINTS = {
     "default": {
         "pip": "",
-        "setuptools": "",
-        "wheel": "",
     },
     "2.6": {
         "pip": "<10",
-        "setuptools": "<37",
-        "wheel": "<0.30",
     },
     "2.7": {
         "pip": "<21.0",
-        "setuptools": "<45",
-        "wheel": "",
     },
     "3.2": {
+        # Pip older than v9.0.0 does not support Requires-Python so we have to manually
+        # constrain the pip, setuptools and wheel versions that are installed at runtime.
         "pip": "<8",
         "setuptools": "<30",
         "wheel": "<0.30",
     },
     "3.3": {
         "pip": "<18",
-        "setuptools": "",
-        "wheel": "<0.30",
     },
     "3.4": {
         "pip": "<19.2",
-        "setuptools": "",
-        "wheel": "",
     },
     "3.5": {
         "pip": "<21.0",
-        "setuptools": "",
-        "wheel": "",
     },
     "3.6": {
         "pip": "<22.0",
-        "setuptools": "",
-        "wheel": "",
     },
     "3.7": {
         "pip": "<24.1",
-        "setuptools": "",
-        "wheel": "",
     },
 }
 
@@ -248,7 +234,7 @@ def detect_newline(f: TextIO) -> str:
 
 
 def generate_one(variant, mapping, *, console, pip_versions):
-    # Determing the correct wheel to download
+    # Determine the correct wheel to download
     pip_version = determine_latest(pip_versions.keys(), constraint=mapping["pip"])
     wheel_url, wheel_hash = pip_versions[pip_version]
 
@@ -264,10 +250,11 @@ def generate_one(variant, mapping, *, console, pip_versions):
         newline = detect_newline(f)
         rendered_template = f.read().format(
             zipfile=encoded_wheel,
-            installed_version=pip_version,
-            pip_version=mapping["pip"],
-            setuptools_version=mapping["setuptools"],
-            wheel_version=mapping["wheel"],
+            bundled_pip_version=pip_version,
+            # These constraints are only used for pip versions that don't support Requires-Python.
+            pip_version_constraint=mapping.get("pip"),
+            setuptools_version_constraint=mapping.get("setuptools"),
+            wheel_version_constraint=mapping.get("wheel"),
             minimum_supported_version=mapping["minimum_supported_version"],
         )
     # Write the script to the correct location

templates/default.py

@@ -5,7 +5,7 @@
 # You may be wondering what this giant blob of binary data here is, you might
 # even be worried that we're up to something nefarious (good for you for being
 # paranoid!). This is a base85 encoding of a zip file, this zip file contains
-# an entire copy of pip (version {installed_version}).
+# an entire copy of pip (version {bundled_pip_version}).
 #
 # Pip is a thing that installs packages, pip itself is a package that someone
 # might want to install, especially if they're looking to run this get-pip.py
@@ -69,13 +69,13 @@ def determine_pip_install_arguments():
     pre_parser.add_argument("--no-wheel", action="store_true")
     pre, args = pre_parser.parse_known_args()
 
-    args.append("pip{pip_version}")
+    args.append("pip")
 
     if include_setuptools(pre):
-        args.append("setuptools{setuptools_version}")
+        args.append("setuptools")
 
     if include_wheel(pre):
-        args.append("wheel{wheel_version}")
+        args.append("wheel")
 
     return ["install", "--upgrade", "--force-reinstall"] + args
 

templates/pre-10.py

@@ -5,7 +5,7 @@
 # You may be wondering what this giant blob of binary data here is, you might
 # even be worried that we're up to something nefarious (good for you for being
 # paranoid!). This is a base85 encoding of a zip file, this zip file contains
-# an entire copy of pip (version {installed_version}).
+# an entire copy of pip (version {bundled_pip_version}).
 #
 # Pip is a thing that installs packages, pip itself is a package that someone
 # might want to install, especially if they're looking to run this get-pip.py
@@ -147,11 +147,11 @@ def parse_args(self, args):
 
     # Add any implicit installations to the end of our args
     if implicit_pip:
-        args += ["pip{pip_version}"]
+        args += ["pip"]
     if implicit_setuptools:
-        args += ["setuptools{setuptools_version}"]
+        args += ["setuptools"]
     if implicit_wheel:
-        args += ["wheel{wheel_version}"]
+        args += ["wheel"]
 
     delete_tmpdir = False
     try:

templates/pre-18.1.py

@@ -5,7 +5,7 @@
 # You may be wondering what this giant blob of binary data here is, you might
 # even be worried that we're up to something nefarious (good for you for being
 # paranoid!). This is a base85 encoding of a zip file, this zip file contains
-# an entire copy of pip (version {installed_version}).
+# an entire copy of pip (version {bundled_pip_version}).
 #
 # Pip is a thing that installs packages, pip itself is a package that someone
 # might want to install, especially if they're looking to run this get-pip.py
@@ -147,11 +147,11 @@ def parse_args(self, args):
 
     # Add any implicit installations to the end of our args
     if implicit_pip:
-        args += ["pip{pip_version}"]
+        args += ["pip"]
     if implicit_setuptools:
-        args += ["setuptools{setuptools_version}"]
+        args += ["setuptools"]
     if implicit_wheel:
-        args += ["wheel{wheel_version}"]
+        args += ["wheel"]
 
     # Add our default arguments
     args = ["install", "--upgrade", "--force-reinstall"] + args

templates/pre-19.3.py

@@ -5,7 +5,7 @@
 # You may be wondering what this giant blob of binary data here is, you might
 # even be worried that we're up to something nefarious (good for you for being
 # paranoid!). This is a base85 encoding of a zip file, this zip file contains
-# an entire copy of pip (version {installed_version}).
+# an entire copy of pip (version {bundled_pip_version}).
 #
 # Pip is a thing that installs packages, pip itself is a package that someone
 # might want to install, especially if they're looking to run this get-pip.py
@@ -147,11 +147,11 @@ def parse_args(self, args):
 
     # Add any implicit installations to the end of our args
     if implicit_pip:
-        args += ["pip{pip_version}"]
+        args += ["pip"]
     if implicit_setuptools:
-        args += ["setuptools{setuptools_version}"]
+        args += ["setuptools"]
     if implicit_wheel:
-        args += ["wheel{wheel_version}"]
+        args += ["wheel"]
 
     # Add our default arguments
     args = ["install", "--upgrade", "--force-reinstall"] + args

templates/pre-21.0.py

@@ -5,7 +5,7 @@
 # You may be wondering what this giant blob of binary data here is, you might
 # even be worried that we're up to something nefarious (good for you for being
 # paranoid!). This is a base85 encoding of a zip file, this zip file contains
-# an entire copy of pip (version {installed_version}).
+# an entire copy of pip (version {bundled_pip_version}).
 #
 # Pip is a thing that installs packages, pip itself is a package that someone
 # might want to install, especially if they're looking to run this get-pip.py
@@ -149,11 +149,11 @@ def cert_parse_args(self, args):
 
     # Add any implicit installations to the end of our args
     if implicit_pip:
-        args += ["pip{pip_version}"]
+        args += ["pip"]
     if implicit_setuptools:
-        args += ["setuptools{setuptools_version}"]
+        args += ["setuptools"]
     if implicit_wheel:
-        args += ["wheel{wheel_version}"]
+        args += ["wheel"]
 
     # Add our default arguments
     args = ["install", "--upgrade", "--force-reinstall"] + args