Updated dot magic, with tests (#268)

* Updated dot magic, with tests

* Added pydot to docs/requirements.txt; is this right place?

* Get the dot command from graphviz

* install graphviz on linux only

* Skip dot tests if not on linux

---------

Co-authored-by: Steven Silvester <steven.silvester@ieee.org>

.github/workflows/tests.yml

@@ -33,6 +33,10 @@ jobs:
       - name: Base Setup
         uses: jupyterlab/maintainer-tools/.github/actions/base-setup@v1
 
+      - name: Install graphviz on Linux
+        if: ${{ startsWith("ubuntu", matrix.os }}
+        run: sudo apt install -y graphviz
+
       - name: Install dependencies
         run: |
           pip install coveralls

docs/requirements.txt

@@ -10,3 +10,4 @@ requests
 sphinx_bootstrap_theme
 numpydoc
 myst-parser
+pydot

metakernel/__init__.py

@@ -10,4 +10,4 @@
 
 __all__ = ['Magic', 'MetaKernel', 'option']
 
-__version__ = '0.29.5'
+__version__ = '0.29.6'

metakernel/magics/dot_magic.py

@@ -23,6 +23,8 @@ def line_dot(self, code):
         except:
             raise Exception("You need to install pydot")
         graph = pydot.graph_from_dot_data(str(code))
+        if isinstance(graph, list):
+            graph = graph[0]
         svg = graph.create_svg()
         if hasattr(svg, "decode"):
             svg = svg.decode("utf-8")
@@ -46,6 +48,8 @@ def cell_dot(self):
         except:
             raise Exception("You need to install pydot")
         graph = pydot.graph_from_dot_data(str(self.code))
+        if isinstance(graph, list):
+            graph = graph[0]
         svg = graph.create_svg()
         if hasattr(svg, "decode"):
             svg = svg.decode("utf-8")

metakernel/magics/tests/test_dot_magic.py

@@ -0,0 +1,25 @@
+import sys
+
+from metakernel.tests.utils import (get_kernel, get_log_text, 
+                                    clear_log_text, EvalKernel)
+
+import pytest
+
+@pytest.mark.skipif(sys.platform != "linux", reason="Requires dot from grahviz")
+def test_dot_magic_cell():
+    kernel = get_kernel(EvalKernel)
+    kernel.do_execute("""%%dot
+
+graph A { a->b };
+""")
+
+    text = get_log_text(kernel)
+    assert "Display Data" in text, text
+
+@pytest.mark.skipif(sys.platform != "linux", reason="Requires dot from grahviz")
+def test_dot_magic_line():
+    kernel = get_kernel(EvalKernel)
+    kernel.do_execute("%dot graph A { a->b };")
+
+    text = get_log_text(kernel)
+    assert "Display Data" in text, text