[python] migrate to pathlib in conf.py (#4427)

docs/conf.py

@@ -20,8 +20,9 @@
 import datetime
 import os
 import sys
-from distutils.dir_util import copy_tree
+from pathlib import Path
 from re import compile
+from shutil import copytree
 from subprocess import PIPE, Popen
 from unittest.mock import Mock
 
@@ -31,9 +32,9 @@ from docutils.parsers.rst import Directive
 from docutils.transforms import Transform
 from sphinx.errors import VersionRequirementError
 
-CURR_PATH = os.path.abspath(os.path.dirname(__file__))
-LIB_PATH = os.path.join(CURR_PATH, os.path.pardir, 'python-package')
-sys.path.insert(0, LIB_PATH)
+CURR_PATH = Path(__file__).parent.absolute()
+LIB_PATH = CURR_PATH.parent / 'python-package'
+sys.path.insert(0, str(LIB_PATH))
 
 INTERNAL_REF_REGEX = compile(r"(?P<url>\.\/.+)(?P<extension>\.rst)(?P<anchor>$|#)")
 
@@ -119,22 +120,20 @@ author = 'Microsoft Corporation'
 
 # The name of an image file (relative to this directory) to place at the top
 # of the sidebar.
-html_logo = os.path.join(CURR_PATH, 'logo', 'LightGBM_logo_grey_text.svg')
+html_logo = str(CURR_PATH / 'logo' / 'LightGBM_logo_grey_text.svg')
 
 # The name of an image file (relative to this directory) to use as a favicon of
 # the docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32
 # pixels large.
-html_favicon = os.path.join(CURR_PATH, '_static', 'images', 'favicon.ico')
+html_favicon = str(CURR_PATH / '_static' / 'images' / 'favicon.ico')
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
 # built documents.
-with open(os.path.join(CURR_PATH, os.path.pardir, 'VERSION.txt'), 'r') as f:
-    # The short X.Y version.
-    version = f.read().strip()
-
-    # The full version, including alpha/beta/rc tags.
-    release = version
+# The short X.Y version.
+version = (CURR_PATH.parent / 'VERSION.txt').read_text(encoding='utf-8').strip().replace('rc', '-rc')
+# The full version, including alpha/beta/rc tags.
+release = version
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
@@ -158,7 +157,7 @@ if C_API:
         'breathe',
     ])
     breathe_projects = {
-        "LightGBM": os.path.join(CURR_PATH, 'doxyoutput', 'xml')
+        "LightGBM": str(CURR_PATH / 'doxyoutput' / 'xml')
     }
     breathe_default_project = "LightGBM"
     breathe_domain_by_extension = {
@@ -195,7 +194,7 @@ htmlhelp_basename = 'LightGBMdoc'
 
 # The name of an image file (relative to this directory) to place at the top of
 # the title page.
-latex_logo = os.path.join(CURR_PATH, 'logo', 'LightGBM_logo_black_text_small.png')
+latex_logo = str(CURR_PATH / 'logo' / 'LightGBM_logo_black_text_small.png')
 
 
 def generate_doxygen_xml(app):
@@ -206,10 +205,9 @@ def generate_doxygen_xml(app):
     app : object
         The application object representing the Sphinx process.
     """
-    input = os.path.join(CURR_PATH, os.path.pardir, 'include', 'LightGBM', 'c_api.h')
     doxygen_args = [
-        f"INPUT={input}",
-        f"OUTPUT_DIRECTORY={os.path.join(CURR_PATH, 'doxyoutput')}",
+        f"INPUT={CURR_PATH.parent / 'include' / 'LightGBM' / 'c_api.h'}",
+        f"OUTPUT_DIRECTORY={CURR_PATH / 'doxyoutput'}",
         "GENERATE_HTML=NO",
         "GENERATE_LATEX=NO",
         "GENERATE_XML=YES",
@@ -226,8 +224,7 @@ def generate_doxygen_xml(app):
     ]
     doxygen_input = '\n'.join(doxygen_args)
     doxygen_input = bytes(doxygen_input, "utf-8")
-    if not os.path.exists(os.path.join(CURR_PATH, 'doxyoutput')):
-        os.makedirs(os.path.join(CURR_PATH, 'doxyoutput'))
+    (CURR_PATH / 'doxyoutput').mkdir(parents=True, exist_ok=True)
     try:
         # Warning! The following code can cause buffer overflows on RTD.
         # Consider suppressing output completely if RTD project silently fails.
@@ -268,10 +265,10 @@ def generate_r_docs(app):
             r-roxygen2=7.1.1=r40h0357c0b_0
     source /home/docs/.conda/bin/activate r_env
     export TAR=/bin/tar
-    cd {os.path.join(CURR_PATH, os.path.pardir)}
+    cd {CURR_PATH.parent}
     export R_LIBS="$CONDA_PREFIX/lib/R/library"
     Rscript build_r.R || exit -1
-    cd {os.path.join(CURR_PATH, os.path.pardir, "lightgbm_r")}
+    cd {CURR_PATH.parent / "lightgbm_r"}
     Rscript -e "roxygen2::roxygenize(load = 'installed')" || exit -1
     Rscript -e "pkgdown::build_site( \
             lazy = FALSE \
@@ -284,7 +281,7 @@ def generate_r_docs(app):
             , new_process = TRUE \
         )
         " || exit -1
-    cd {os.path.join(CURR_PATH, os.path.pardir)}
+    cd {CURR_PATH.parent}
     """
     try:
         # Warning! The following code can cause buffer overflows on RTD.
@@ -312,9 +309,9 @@ def setup(app):
     app : object
         The application object representing the Sphinx process.
     """
-    first_run = not os.path.exists(os.path.join(CURR_PATH, '_FIRST_RUN.flag'))
+    first_run = not (CURR_PATH / '_FIRST_RUN.flag').exists()
     if first_run and RTD:
-        open(os.path.join(CURR_PATH, '_FIRST_RUN.flag'), 'w').close()
+        (CURR_PATH / '_FIRST_RUN.flag').touch()
     if C_API:
         app.connect("builder-inited", generate_doxygen_xml)
     else:
@@ -323,8 +320,8 @@ def setup(app):
         if first_run:
             app.connect("builder-inited", generate_r_docs)
         app.connect("build-finished",
-                    lambda app, _: copy_tree(os.path.join(CURR_PATH, os.path.pardir, "lightgbm_r", "docs"),
-                                             os.path.join(app.outdir, "R"), verbose=0))
+                    lambda app, _: copytree(CURR_PATH.parent / "lightgbm_r" / "docs",
+                                            Path(app.outdir) / "R"))
     app.add_transform(InternalRefTransform)
     add_js_file = getattr(app, 'add_js_file', False) or app.add_javascript
     add_js_file("js/script.js")