python.2: fix tests, use source checkers and more python3 features

Check the whole code with flake8, pylint and mypy.

Report all possible errors with extensive context.

Demonstrate iterators, decorators, functional tools, chain maps,
dataclasses, match statements, assignments expressions.

Implement environments with python chain maps.

Rewrite the reader without external dependencies (but inspired by the
ptk library).  The motivation was that no external library is fully
type-checked for now.

Avoid name clashes when possible (print, read, readline, types).

Write the readline history file at exit, not after each prompt.

Replace printer.pr_str as methods of MAL objects.  This is idiomatic
python, and improves the error reporting.

Change some representations so that the python equality matches the
MAL equality.  The recursion is now implicit.

Remove -O from ./run.  It took me a while to understand that run-time
assertions were disabled!  MAL is about development, not performance.

Dispatch the special forms from a dict, for readability (pylint
rightfully complains that there are too many return statements in
eval_()).

Copy the recursion overflow fix, the python interaction from the first
python implementation.

Add tests detecting that nil false 0 () [] "" are distinct, and that 0
() are not False when tested (in python False == 0 and an empty
container is tested ).

Add tests checking that metadata does not affect equality (they do
with a naive python dataclass).

README.md

@@ -971,13 +971,10 @@ python stepX_YYY.py
 
 ### Python.2 (3.X)
 
-The second Python implementation makes heavy use of type annotations and uses the Arpeggio parser library.
-
-```
-# Recommended: do these steps in a Python virtual environment.
-pip3 install Arpeggio==1.9.0
-python3 stepX_YYY.py
-```
+The second Python implementation is checked for style and types
+(flake8, pylint, mypy).  It reports all errors with details.
+It demonstrates iterators, decorators, functional tools, chain maps,
+dataclasses, introspection, match statements, assignement expressions.
 
 ### RPython
 

impls/python.2/Dockerfile

@@ -9,10 +9,8 @@ MAINTAINER Joel Martin <[email protected]>
 RUN apt-get -y update
 
 # Required for running tests
-RUN apt-get -y install make python
-
-# Some typical implementation and test requirements
-RUN apt-get -y install curl libreadline-dev libedit-dev
+RUN apt-get -y install make python3
+RUN ln -fs /usr/bin/python3 /usr/local/bin/python
 
 RUN mkdir -p /mal
 WORKDIR /mal
@@ -21,11 +19,5 @@ WORKDIR /mal
 # Specific implementation requirements
 ##########################################################
 
-# Nothing additional needed for python
-RUN apt-get -y install python3
-
-# For dist packaging
-RUN apt-get -y install zip
-
-# Pypi modules
-RUN apt-get -y install python3-pip && pip3 install Arpeggio==1.9.0
+# For checking:
+# RUN apt-get -y install flake8 mypy pylint

impls/python.2/Makefile

@@ -1,6 +1,26 @@
+# make check sources=reader.py    may be convenient
+sources ?= *.py
+
+f8 += D100 # Missing docstring in public module
+f8 += D101 # Missing docstring in public class
+f8 += D102 # Missing docstring in public method
+f8 += D103 # Missing docstring in public function
+f8 += D105 # Missing docstring in magic method
+f8 += D107 # Missing docstring in __init__
+f8 += I100 # order of import statements (incompatible with pylint)
+f8 += W503 # line break before binary operator (incompatible with 504)
+pl += missing-module-docstring
+pl += missing-class-docstring
+pl += missing-function-docstring
+pl += R0801 # Similar lines in 2 files (steps...)
+
 all:
-	true
 
-.PHONY: clean
+check:
+	pylint --disable=$(shell echo $(pl) | sed 's/ /,/g') $(sources)
+	mypy $(sources)
+	flake8 --ignore=$(shell echo $(f8) | sed 's/ /,/g') $(sources)
 
 clean:
+	rm -f *~
+	rm -fr __pycache__/ .mypy_cache/