refactor(toolchains): better sha256 printing helper (#3028)

Before this PR the toolchain sha256 values would be printed in a way
that would require further text manipulation. Now we print the values
that need to be just copy pasted.

Whilst at it simplify the `curl` command to remove the conditional.

Testing done:
```
$ bazel run //python/private:print_toolchains_checksums --//python/config_settings:python_version=""
# And then paste all of the output into the inside of the TOOL_VERSIONS
```

Work towards #2704

Author: aignas

python/private/BUILD.bazel

@@ -16,7 +16,7 @@ load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
 load("@bazel_skylib//rules:common_settings.bzl", "bool_setting")
 load("//python:py_binary.bzl", "py_binary")
 load("//python:py_library.bzl", "py_library")
-load("//python:versions.bzl", "print_toolchains_checksums")
+load(":print_toolchain_checksums.bzl", "print_toolchains_checksums")
 load(":py_exec_tools_toolchain.bzl", "current_interpreter_executable")
 load(":sentinel.bzl", "sentinel")
 load(":stamp.bzl", "stamp_build_setting")

python/private/print_toolchain_checksums.bzl

@@ -0,0 +1,92 @@
+"""Print the toolchain versions.
+"""
+
+load("//python:versions.bzl", "TOOL_VERSIONS", "get_release_info")
+load("//python/private:text_util.bzl", "render")
+load("//python/private:version.bzl", "version")
+
+def print_toolchains_checksums(name):
+    """A macro to print checksums for a particular Python interpreter version.
+
+    Args:
+        name: {type}`str`: the name of the runnable target.
+    """
+    by_version = {}
+
+    for python_version, metadata in TOOL_VERSIONS.items():
+        by_version[python_version] = _commands_for_version(
+            python_version = python_version,
+            metadata = metadata,
+        )
+
+    all_commands = sorted(
+        by_version.items(),
+        key = lambda x: version.key(version.parse(x[0], strict = True)),
+    )
+    all_commands = [x[1] for x in all_commands]
+
+    template = """\
+cat > "$@" <<'EOF'
+#!/bin/bash
+
+set -o errexit -o nounset -o pipefail
+
+echo "Fetching hashes..."
+
+{commands}
+EOF
+    """
+
+    native.genrule(
+        name = name,
+        srcs = [],
+        outs = ["print_toolchains_checksums.sh"],
+        cmd = select({
+            "//python/config_settings:is_python_{}".format(version_str): template.format(
+                commands = commands,
+            )
+            for version_str, commands in by_version.items()
+        } | {
+            "//conditions:default": template.format(commands = "\n".join(all_commands)),
+        }),
+        executable = True,
+    )
+
+def _commands_for_version(*, python_version, metadata):
+    lines = []
+    lines += [
+        "cat <<EOB",  # end of block
+        "    \"{python_version}\": {{".format(python_version = python_version),
+        "        \"url\": \"{url}\",".format(url = metadata["url"]),
+        "        \"sha256\": {",
+    ]
+
+    for platform in metadata["sha256"].keys():
+        for release_url in get_release_info(platform, python_version)[1]:
+            # Do lines one by one so that the progress is seen better and use cat for ease of quotation
+            lines += [
+                "EOB",
+                "cat <<EOB",
+                "            \"{platform}\": \"$$({get_sha256})\",".format(
+                    platform = platform,
+                    get_sha256 = "curl --silent --show-error --location --fail {release_url_sha256}".format(
+                        release_url = release_url,
+                        release_url_sha256 = release_url + ".sha256",
+                    ),
+                ),
+            ]
+
+    prefix = metadata["strip_prefix"]
+    prefix = render.indent(
+        render.dict(prefix) if type(prefix) == type({}) else repr(prefix),
+        indent = " " * 8,
+    ).lstrip()
+
+    lines += [
+        "        },",
+        "        \"strip_prefix\": {strip_prefix},".format(strip_prefix = prefix),
+        "    },",
+        "EOB",
+    ]
+
+    return "\n".join(lines)

python/versions.bzl

@@ -32,6 +32,9 @@ DEFAULT_RELEASE_BASE_URL = "https://github.com/astral-sh/python-build-standalone
 # the hashes:
 #   bazel run //python/private:print_toolchains_checksums --//python/config_settings:python_version={major}.{minor}.{patch}
 #
+# To print hashes for all of the specified versions, run:
+#   bazel run //python/private:print_toolchains_checksums --//python/config_settings:python_version=""
+#
 # Note, to users looking at how to specify their tool versions, coverage_tool version for each
 # interpreter can be specified by:
 #   "3.8.10": {
@@ -1092,57 +1095,6 @@ def get_release_info(platform, python_version, base_url = DEFAULT_RELEASE_BASE_U
 
     return (release_filename, rendered_urls, strip_prefix, patches, patch_strip)
 
-def print_toolchains_checksums(name):
-    """A macro to print checksums for a particular Python interpreter version.
-
-    Args:
-        name: {type}`str`: the name of the runnable target.
-    """
-    all_commands = []
-    by_version = {}
-    for python_version in TOOL_VERSIONS.keys():
-        by_version[python_version] = _commands_for_version(python_version)
-        all_commands.append(_commands_for_version(python_version))
-
-    template = """\
-cat > "$@" <<'EOF'
-#!/bin/bash
-
-set -o errexit -o nounset -o pipefail
-
-echo "Fetching hashes..."
-
-{commands}
-EOF
-    """
-
-    native.genrule(
-        name = name,
-        srcs = [],
-        outs = ["print_toolchains_checksums.sh"],
-        cmd = select({
-            "//python/config_settings:is_python_{}".format(version): template.format(
-                commands = commands,
-            )
-            for version, commands in by_version.items()
-        } | {
-            "//conditions:default": template.format(commands = "\n".join(all_commands)),
-        }),
-        executable = True,
-    )
-
-def _commands_for_version(python_version):
-    return "\n".join([
-        "echo \"{python_version}: {platform}: $$(curl --location --fail {release_url_sha256} 2>/dev/null || curl --location --fail {release_url} 2>/dev/null | shasum -a 256 | awk '{{ print $$1 }}')\"".format(
-            python_version = python_version,
-            platform = platform,
-            release_url = release_url,
-            release_url_sha256 = release_url + ".sha256",
-        )
-        for platform in TOOL_VERSIONS[python_version]["sha256"].keys()
-        for release_url in get_release_info(platform, python_version)[1]
-    ])
-
 def gen_python_config_settings(name = ""):
     for platform in PLATFORMS.keys():
         native.config_setting(