Avoid ResourceWarning: unclosed file

A number of warnings showed up when running e.g.
PYTHONWARNINGS=always python build_examples.py
See #309 (comment)

Fix: All open() calls should be in a "with open() as x" statement
to ensure closing the file when exiting the block in any way.
Otherwise, use the new file_read_text() or file_write_text() to
read or write the whole utf-8 text file and closing it.

src/wireviz/Harness.py

@@ -44,11 +44,10 @@
 )
 from wireviz.wv_helper import (
     awg_equiv,
+    file_write_text,
     flatten2d,
     is_arrow,
     mm2_equiv,
-    open_file_read,
-    open_file_write,
     tuplelist2tsv,
 )
 from wireviz.wv_html import generate_html_output
@@ -693,7 +692,7 @@ def output(
         # BOM output
         bomlist = bom_list(self.bom())
         if "tsv" in fmt:
-            open_file_write(f"{filename}.bom.tsv").write(tuplelist2tsv(bomlist))
+            file_write_text(f"{filename}.bom.tsv", tuplelist2tsv(bomlist))
         if "csv" in fmt:
             # TODO: implement CSV output (preferrably using CSV library)
             print("CSV output is not yet supported")

src/wireviz/wireviz.py

@@ -14,9 +14,9 @@
 from wireviz.Harness import Harness
 from wireviz.wv_helper import (
     expand,
+    file_read_text,
     get_single_key_and_value,
     is_arrow,
-    open_file_read,
     smart_file_resolve,
 )
 
@@ -408,7 +408,7 @@ def _get_yaml_data_and_path(inp: Union[str, Path, Dict]) -> (Dict, Path):
         try:
             yaml_path = Path(inp).expanduser().resolve(strict=True)
             # if no FileNotFoundError exception happens, get file contents
-            yaml_str = open_file_read(yaml_path).read()
+            yaml_str = file_read_text(yaml_path)
         except (FileNotFoundError, OSError) as e:
             # if inp is a long YAML string, Pathlib will raise OSError: [errno.ENAMETOOLONG]
             # (in Windows, it seems OSError [errno.EINVAL] might be raised in some cases)

src/wireviz/wv_cli.py

@@ -11,7 +11,7 @@
 
 import wireviz.wireviz as wv
 from wireviz import APP_NAME, __version__
-from wireviz.wv_helper import open_file_read
+from wireviz.wv_helper import file_read_text
 
 format_codes = {
     # "c": "csv",
@@ -111,7 +111,7 @@ def wireviz(file, format, prepend, output_dir, output_name, version):
                 raise Exception(f"File does not exist:\n{prepend_file}")
             print("Prepend file:", prepend_file)
 
-            prepend_input += open_file_read(prepend_file).read() + "\n"
+            prepend_input += file_read_text(prepend_file) + "\n"
     else:
         prepend_input = ""
 
@@ -130,7 +130,7 @@ def wireviz(file, format, prepend, output_dir, output_name, version):
             "Output file: ", f"{Path(_output_dir / _output_name)}.{output_formats_str}"
         )
 
-        yaml_input = open_file_read(file).read()
+        yaml_input = file_read_text(file)
         file_dir = file.parent
 
         yaml_input = prepend_input + yaml_input

src/wireviz/wv_helper.py

@@ -113,18 +113,31 @@ def clean_whitespace(inp):
 
 
 def open_file_read(filename):
+    """Open utf-8 encoded text file for reading - remember closing it when finished"""
     # TODO: Intelligently determine encoding
     return open(filename, "r", encoding="UTF-8")
 
 
 def open_file_write(filename):
+    """Open utf-8 encoded text file for writing - remember closing it when finished"""
     return open(filename, "w", encoding="UTF-8")
 
 
 def open_file_append(filename):
+    """Open utf-8 encoded text file for appending - remember closing it when finished"""
     return open(filename, "a", encoding="UTF-8")
 
 
+def file_read_text(filename: str) -> str:
+    """Read utf-8 encoded text file, close it, and return the text"""
+    return Path(filename).read_text(encoding="utf-8")
+
+
+def file_write_text(filename: str, text: str) -> int:
+    """Write utf-8 encoded text file, close it, and return the number of characters written"""
+    return Path(filename).write_text(text, encoding="utf-8")
+
+
 def is_arrow(inp):
     """
     Matches strings of one or multiple `-` or `=` (but not mixed)
@@ -144,10 +157,10 @@ def aspect_ratio(image_src):
     try:
         from PIL import Image
 
-        image = Image.open(image_src)
-        if image.width > 0 and image.height > 0:
-            return image.width / image.height
-        print(f"aspect_ratio(): Invalid image size {image.width} x {image.height}")
+        with Image.open(image_src) as image:
+            if image.width > 0 and image.height > 0:
+                return image.width / image.height
+            print(f"aspect_ratio(): Invalid image size {image.width} x {image.height}")
     # ModuleNotFoundError and FileNotFoundError are the most expected, but all are handled equally.
     except Exception as error:
         print(f"aspect_ratio(): {type(error).__name__}: {error}")

src/wireviz/wv_html.py

@@ -9,9 +9,9 @@
 from wireviz.svgembed import data_URI_base64
 from wireviz.wv_gv_html import html_line_breaks
 from wireviz.wv_helper import (
+    file_read_text,
+    file_write_text,
     flatten2d,
-    open_file_read,
-    open_file_write,
     smart_file_resolve,
 )
 
@@ -35,14 +35,14 @@ def generate_html_output(
         # fall back to built-in simple template if no template was provided
         templatefile = Path(__file__).parent / "templates/simple.html"
 
-    html = open_file_read(templatefile).read()
+    html = file_read_text(templatefile)
 
     # embed SVG diagram (only if used)
     def svgdata() -> str:
         return re.sub(
             "^<[?]xml [^?>]*[?]>[^<]*<!DOCTYPE [^>]*>",
             "<!-- XML and DOCTYPE declarations from SVG file removed -->",
-            open_file_read(f"{filename}.tmp.svg").read(),
+            file_read_text(f"{filename}.tmp.svg"),
             1,
         )
 
@@ -128,4 +128,4 @@ def replacement_if_used(key: str, func: Callable[[], str]) -> None:
     pattern = re.compile("|".join(replacements_escaped))
     html = pattern.sub(lambda match: replacements[match.group(0)], html)
 
-    open_file_write(f"{filename}.html").write(html)
+    file_write_text(f"{filename}.html", html)