look into %PATH% for graphviz, pandoc, latex

src/pyquickhelper/helpgen/utils_sphinx_doc_helpers.py

@@ -778,6 +778,23 @@ def remove_some_indent(s):
         return "\n".join(keep)
     else :
         return s
+
+def find_in_PATH(prog):
+    """
+    look into every path mentioned in ``%PATH%`` a specific file,
+    it raises an exception if not Found
+    
+    @param      prog        program to look for
+    @return                 path
+    
+    .. versionadded:: 0.9
+    """
+    path = os.environ["PATH"]
+    for p in path.split(";"):
+        f = os.path.join(p, prog)
+        if os.path.exists(f):
+            return p
+    return None
 
 def find_graphviz_dot():
     """
@@ -786,26 +803,39 @@ def find_graphviz_dot():
     assuming it was installed in a standard folder: ``C:\Program Files\MiKTeX 2.9\miktex\bin\x64``
 
     @return         path to dot
+    
+    :raises FileNotFoundError: if graphviz not found
+    
+    .. versionadded:: 0.9
     """
     if sys.platform.startswith("win"):
         version = range(34,45)
         for v in version:
             graphviz_dot = r"C:\Program Files (x86)\Graphviz2.{0}\bin\dot.exe".format(v)
             if os.path.exists(graphviz_dot):
                 return graphviz_dot
-
-        raise FileNotFoundError("unable to find graphviz, look into paths such as: " + graphviz_dot)
+        p = find_in_PATH("dot.exe")
+        if p is None:
+            raise FileNotFoundError("unable to find graphviz, look into paths such as: " + graphviz_dot)
+        else:
+            return p
     else:
         # linux
         return "dot"
 
 def find_latex_path():
     """
     @return ``C:\Program Files\MiKTeX 2.9\miktex\bin\x64``
+    
+    :raises FileNotFoundError: if latex not found
+    
+    .. versionadded:: 0.9
     """
     if sys.platform.startswith("win"):
         latex = r"C:\Program Files\MiKTeX 2.9\miktex\bin\x64"
         if not os.path.exists(latex):
+            latex = find_in_PATH("latex.exe")
+        if latex is None or not os.path.exists(latex):
             raise FileNotFoundError("unable to find latex (miktex), look into paths such as: " + latex)
     else:
         # linux
@@ -816,6 +846,8 @@ def find_pandoc_path():
     determines pandoc location
 
     @return         path to pandoc
+    
+    .. versionadded:: 0.9
     """
     if sys.platform.startswith("win"):
         path = os.environ["USERPROFILE"]
@@ -832,7 +864,11 @@ def find_pandoc_path():
                     if os.path.exists(pandoc) :
                         return pandoc
                     tries.append(pandoc)
-            raise FileNotFoundError("unable to find pandoc, look into paths such as:\n" + "\n".join(tries))
+            pandoc = find_in_PATH("pandoc.exe")
+            if pandoc is None:
+                raise FileNotFoundError("unable to find pandoc, look into paths such as:\n" + "\n".join(tries))
+            else:
+                return pandoc
         else :
             return pandoc
     else: