From f0b9de01183d4a4eb9cd6ff7fb98cf4d37693b88 Mon Sep 17 00:00:00 2001
From: Miika Alonen <amiika@gmail.com>
Date: Sat, 18 Mar 2023 00:01:48 +0200
Subject: [PATCH] Adding checks if music21 is installed

Music21 is optional dependency
---
 ziffers/converters.py | 78 +++++++++++++++++++++++++------------------
 1 file changed, 45 insertions(+), 33 deletions(-)

diff --git a/ziffers/converters.py b/ziffers/converters.py
index e9902c1..36b124a 100644
--- a/ziffers/converters.py
+++ b/ziffers/converters.py
@@ -1,10 +1,18 @@
 """Collection of converters"""
-from music21 import converter, note, stream, meter, chord, environment
 from ziffers import zparse, Ziffers, Pitch, Rest, Chord
 
+try:
+    from music21 import converter, note, stream, meter, chord, environment
+    music21_imported: bool = True
+except ImportError:
+    music21_imported: bool = False
 
 def to_music21(expression: str | Ziffers, **options):
     """Helper for passing options to the parser"""
+
+    if not music21_imported:
+        raise ImportError("Install Music21 library")
+
     converter.registerSubconverter(ZiffersMusic21)
 
     if isinstance(expression, Ziffers):
@@ -32,40 +40,44 @@ def set_musescore_path(path: str):
     settings["musescoreDirectPNGPath"] = path
 
 
-class ZiffersMusic21(converter.subConverters.SubConverter):
-    """Ziffers converter to Music21"""
+if music21_imported:
 
-    registerFormats = ("ziffers",)
-    registerInputExtensions = ("zf",)
+    # pylint: disable=locally-disabled, invalid-name, unused-argument, attribute-defined-outside-init
+    class ZiffersMusic21(converter.subConverters.SubConverter):
+        """Ziffers converter to Music21"""
 
-    def parseData(self, dataString, number=None):
-        """Parses Ziffers string to Music21 object"""
-        # Look for options in keywords object
-        keywords = self.keywords["keywords"]
-        if "ziffers" in keywords:
-            options = keywords["ziffers"]
-            if "preparsed" in options:
-                parsed = options["preparsed"]
+        registerFormats = ("ziffers",)
+        registerInputExtensions = ("zf",)
+
+        def parseData(self, dataString, number=None):
+            """Parses Ziffers string to Music21 object"""
+            # Look for options in keywords object
+            keywords = self.keywords["keywords"]
+            if "ziffers" in keywords:
+                options = keywords["ziffers"]
+                if "preparsed" in options:
+                    parsed = options["preparsed"]
+                else:
+                    parsed = zparse(dataString, **options)
             else:
-                parsed = zparse(dataString, **options)
-        else:
-            parsed = zparse(dataString)
+                parsed = zparse(dataString)
 
-        note_stream = stream.Part()
-        if "time" in options:
-            m_item = meter.TimeSignature(options["time"])  # Common time
-        else:
-            m_item = meter.TimeSignature("c")  # Common time
+            note_stream = stream.Part()
+            if "time" in options:
+                m_item = meter.TimeSignature(options["time"])  # Common time
+            else:
+                m_item = meter.TimeSignature("c")  # Common time
 
-        note_stream.insert(0, m_item)
-        for item in parsed:
-            if isinstance(item, Pitch):
-                m_item = note.Note(item.note)
-                m_item.duration.quarterLength = item.duration * 4
-            elif isinstance(item, Rest):
-                m_item = note.Rest(item.duration * 4)
-            elif isinstance(item, Chord):
-                m_item = chord.Chord(item.notes)
-                m_item.duration.quarterLength = item.duration * 4
-            note_stream.append(m_item)
-        self.stream = note_stream.makeMeasures()
+            note_stream.insert(0, m_item)
+            for item in parsed:
+                if isinstance(item, Pitch):
+                    m_item = note.Note(item.note)
+                    m_item.duration.quarterLength = item.duration * 4
+                elif isinstance(item, Rest):
+                    m_item = note.Rest(item.duration * 4)
+                elif isinstance(item, Chord):
+                    m_item = chord.Chord(item.notes)
+                    m_item.duration.quarterLength = item.duration * 4
+                note_stream.append(m_item)
+            # TODO: Is this ok?
+            self.stream = note_stream.makeMeasures()
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