Add support for setting environment variables.

Specified as a list of NAME=VALUE lines in the pgfutils.environment
configuration option.

Author: bcbnz

doc/config.md

@@ -203,6 +203,48 @@ This is a comma-separated list of extra libraries to install file tracking on.
 See the [file tracking](file_tracking.md) documentation for more details.
 
 
+### Environment variables
+
+Environment variables to set can be specified using the multi-line option
+``environment``. Each line represents one environment variable in the format
+``name = value``:
+
+```INI
+[pgfutils]
+environment =
+  name1 = value1
+  name2 = value2
+```
+
+All names and values are processed and set as strings; any leading or trailing
+spaces around the names or values will be stripped. Existing environment
+variables of the same name will be overwritten. This means that if you specify
+the same variable multiple times the last value will be used. For example, the
+configuration
+
+```INI
+[pgfutils]
+environment =
+  name1 = value1
+  name2 = value2
+  name1 = value3
+```
+
+will result in ``name1`` being set to ``value3``. The variables are set during
+the call to ``setup_figure()``, so any libraries that read the environment
+variables must be imported after this call.
+
+Note that the ``PGFUTILS_TRACK_FILES`` variable described in the [file tracking
+documentation](file_tracking.md) can be configured through this option, for
+example to output tracked files to stdout:
+
+```INI
+[pgfutils]
+environment =
+  PGFUTILS_TRACK_FILES = 1
+```
+
+
 Path settings
 -------------
 

extras/pgfutils.cfg

@@ -114,6 +114,13 @@ preamble_substitute = false
 # Extra library-specific file trackers to install.
 extra_tracking =
 
+# Environment variables to set. This should be a multi-line value; place one or
+# more spaces between each subsequenct line (these spaces will be removed when
+# parsing the configuration). Each line should be in the format name = value,
+# with the value being read as a string, and leading and trailing spaces being
+# removed from both the name and the value.
+environment =
+
 
 
 # Path setup.

pgfutils.py

@@ -36,7 +36,7 @@
 
 """
 
-__version__ = "1.4.0"
+__version__ = "1.5.0"
 
 # We don't import Matplotlib here as this brings in NumPy. In turn, NumPy
 # caches a reference to the io.open() method as part of its data loading
@@ -410,6 +410,7 @@ def _config_reset():
             'figure_background': '',
             'axes_background': 'white',
             'extra_tracking': '',
+            'environment': '',
         },
 
         'paths': {
@@ -705,24 +706,39 @@ def setup_figure(width=1.0, height=1.0, columns=None, margin=False,
     """
     global _config, _interactive
 
-    # Need to install our file trackers (if desired)
-    # before we import Matplotlib.
-    if 'PGFUTILS_TRACK_FILES' in os.environ:
-        _install_standard_file_trackers()
-
     # Reset the configuration.
     _config_reset()
 
     # Load configuration from a local file if one exists.
     if os.path.exists('pgfutils.cfg'):
         _config.read('pgfutils.cfg')
+        _file_tracker.filenames.add(("r", "pgfutils.cfg"))
 
     # And anything given in the function call.
     if kwargs:
         _config.read_kwargs(**kwargs)
 
-    # Now we can add any extra trackers specified in the config.
+    # Set environment variables specified in the configuration.
+    for line in _config['pgfutils']['environment'].splitlines():
+        line = line.strip()
+        if not line:
+            continue
+
+        # Check the variables are formatted correctly.
+        if '=' not in line:
+            raise ValueError(
+                "Environment variables should be in the form NAME=VALUE. "
+                "The line '{}' does not match this.".format(line)
+            )
+
+        # And set them.
+        key, value = line.split("=", 1)
+        os.environ[key.strip()] = value.strip()
+
+    # Install file trackers if desired. This must be done before anything which
+    # imports Matplotlib.
     if 'PGFUTILS_TRACK_FILES' in os.environ:
+        _install_standard_file_trackers()
         extra = _config['pgfutils']['extra_tracking'].strip()
         if extra:
             _install_extra_file_trackers(extra.split(","))

tests/sources/environment/check_set/basic.py

@@ -0,0 +1,14 @@
+from pgfutils import setup_figure, save
+setup_figure()
+
+import os
+
+name1 = os.environ.get("name1", "not set")
+name2 = os.environ.get("name2", "not set")
+
+if name1 != "value1":
+    raise ValueError("Incorrect value ({}) for environment variable name1".format(name1))
+if name2 != "value2":
+    raise ValueError("Incorrect value ({}) for environment variable name2".format(name2))
+
+save()

tests/sources/environment/check_set/override.py

@@ -0,0 +1,17 @@
+import os
+os.environ["name1"] = "original value"
+
+from pgfutils import setup_figure, save
+setup_figure()
+
+import os
+
+name1 = os.environ.get("name1", "not set")
+name2 = os.environ.get("name2", "not set")
+
+if name1 != "value1":
+    raise ValueError("Incorrect value ({}) for environment variable name1".format(name1))
+if name2 != "value2":
+    raise ValueError("Incorrect value ({}) for environment variable name2".format(name2))
+
+save()

tests/sources/environment/check_set/pgfutils.cfg

@@ -0,0 +1,4 @@
+[pgfutils]
+environment=
+  name1=value1
+  name2 = value2   

tests/sources/environment/invalid/basic.py

@@ -0,0 +1,3 @@
+from pgfutils import setup_figure, save
+setup_figure()
+save()

tests/sources/environment/invalid/pgfutils.cfg

@@ -0,0 +1,4 @@
+[pgfutils]
+environment=
+  line1=ok
+  line2 should fail

tests/sources/environment/repeated/basic.py

@@ -0,0 +1,14 @@
+from pgfutils import setup_figure, save
+setup_figure()
+
+import os
+
+name1 = os.environ.get("name1", "not set")
+name2 = os.environ.get("name2", "not set")
+
+if name1 != "value3":
+    raise ValueError("Incorrect value ({}) for environment variable name1".format(name1))
+if name2 != "value2":
+    raise ValueError("Incorrect value ({}) for environment variable name2".format(name2))
+
+save()

tests/sources/environment/repeated/pgfutils.cfg

@@ -0,0 +1,5 @@
+[pgfutils]
+environment=
+  name1=value1
+  name2 = value2   
+  name1=value3