[util] Allow optional tools in check_tool_requirements

tool_requirements.py lists minimum versions for tools, but the
distinction between "tools that absolutely need to be installed" and
"the minimum version of a tool if you want to run it" was baked in to
check_tool_requirements.py

This patch moves that distinction to the (more user-editable)
tool_requirements.py. Tools that are marked as_needed aren't checked
unless they are passed on the command line to
check_tool_requirements.py.

Signed-off-by: Rupert Swarbrick <[email protected]>

doc/ug/install_instructions/index.md

@@ -41,7 +41,7 @@ For packages listed below without a version number we have not determined a mini
   GCC 5 or Clang 3.5 should meet this requirement.
 * clang-format.
   The use of clang-format 6.0 is recommended to match the formatting enforced when submitting a pull request.
-* [ninja](https://ninja-build.org/)  {{< tool_version "ninja-build" >}}
+* [ninja](https://ninja-build.org/)  {{< tool_version "ninja" >}}
 * Bash
 * curl
 * xz tools

tool_requirements.py

@@ -4,10 +4,32 @@
 
 # Version requirements for various tools. Checked by tooling (e.g. fusesoc),
 # and inserted into the documentation.
+#
+# Entries are keyed by tool name. The value is either a string giving the
+# minimum version number or is a dictionary. If a dictionary, the following
+# keys are recognised:
+#
+#    min_version: Required string. Minimum version number.
+#
+#    as_needed:   Optional bool. Defaults to False. If set, this tool is not
+#                 automatically required. If it is asked for, the rest of the
+#                 entry gives the required version.
+#
 __TOOL_REQUIREMENTS__ = {
     'edalize': '0.2.0',
-    'hugo_extended': '0.71.0',
-    'ninja-build': '1.8.2',
-    'verible': 'v0.0-808-g1e17daa',
+    'ninja': '1.8.2',
     'verilator': '4.104',
+
+    'hugo_extended': {
+        'min_version': '0.71.0',
+        'as_needed': True
+    },
+    'verible': {
+        'min_version': 'v0.0-808-g1e17daa',
+        'as_needed': True
+    },
+    'vcs': {
+        'min_version': '2020.03-SP2',
+        'as_needed': True
+    }
 }

util/build_docs.py

@@ -38,8 +38,8 @@
 
 # Version of hugo extended to be used to build the docs
 try:
-    tool_requirements = check_tool_requirements.read_tool_requirements()
-    HUGO_EXTENDED_VERSION = tool_requirements['hugo_extended']
+    TOOL_REQUIREMENTS = check_tool_requirements.read_tool_requirements()
+    HUGO_EXTENDED_VERSION = TOOL_REQUIREMENTS['hugo_extended'].min_version
 except Exception as e:
     print("Unable to get required hugo version: %s" % str(e), file=sys.stderr)
     sys.exit(1)
@@ -241,16 +241,12 @@ def generate_tool_versions():
     The version number per tool will be saved in outdir-generated/version_$TOOL_NAME.txt
     """
 
-    # Populate __TOOL_REQUIREMENTS__
-    requirements_file = str(SRCTREE_TOP.joinpath("tool_requirements.py"))
-    exec(open(requirements_file).read(), globals())
-
     # And then write a version file for every tool.
-    for tool in __TOOL_REQUIREMENTS__:  # noqa: F821
+    for tool, req in TOOL_REQUIREMENTS.items():
         version_path = config["outdir-generated"].joinpath('version_' + tool + '.txt')
         version_path.parent.mkdir(parents=True, exist_ok=True)
         with open(str(version_path), mode='w') as fout:
-            fout.write(__TOOL_REQUIREMENTS__[tool])  # noqa: F821
+            fout.write(req.min_version)
 
 
 def generate_dif_docs():