Improve ALE project style checking

* The project style linter now runs while you type.
* Now the scripts for checking the project require blank lines.
* Many style issues have been found and fixed.

2 files changed, 129 insertions, 3 deletions

diff --git a/test/script/block-padding-checker b/test/script/block-padding-checker
new file mode 100755
index 00000000..b13c9b92
--- /dev/null
+++ b/test/script/block-padding-checker
@@ -0,0 +1,117 @@
+#!/usr/bin/env python
+"""
+This script checks for missing or forbidden blank lines before or after
+particular Vim commands. This script ensures that VimL scripts are padded
+correctly, so they are easier to read.
+"""
+
+import sys
+import re
+
+INDENTATION_RE = re.compile(r'^ *')
+COMMENT_LINE_RE = re.compile(r'^ *"')
+COMMAND_RE = re.compile(r'^ *([a-zA-Z]+)')
+
+START_BLOCKS = set(['if', 'for', 'while', 'try', 'function'])
+END_BLOCKS = set(['endif', 'endfor', 'endwhile', 'endtry', 'endfunction'])
+MIDDLE_BLOCKS = set(['else', 'elseif', 'catch', 'finally'])
+TERMINATORS = set(['return', 'throw'])
+
+WHITESPACE_BEFORE_SET = START_BLOCKS | TERMINATORS
+WHITESPACE_FORBIDDEN_BEFORE_SET = END_BLOCKS | MIDDLE_BLOCKS
+WHITESPACE_AFTER_SET = END_BLOCKS
+WHITESPACE_FORBIDDEN_AFTER_SET = START_BLOCKS | MIDDLE_BLOCKS
+
+
+def remove_comment_lines(line_iter):
+    for line_number, line in enumerate(line_iter, 1):
+        if not COMMENT_LINE_RE.match(line):
+            yield (line_number, line)
+
+
+def check_lines(line_iter):
+    previous_indentation_level = None
+    previous_command = None
+    previous_line_blank = False
+
+    for line_number, line in remove_comment_lines(line_iter):
+        if len(line) == 0:
+            # Check for commands where we shouldn't have blank lines after
+            # them, like `else` or the start of blocks like `function`.
+            if (
+                previous_command is not None
+                and previous_command in WHITESPACE_FORBIDDEN_AFTER_SET
+            ):
+                yield (
+                    line_number,
+                    'Blank line forbidden after `%s`' % (command,)
+                )
+
+            previous_line_blank = True
+            previous_command = None
+        else:
+            indentation_level = INDENTATION_RE.match(line).end()
+            command_match = COMMAND_RE.match(line)
+
+            if command_match:
+                command = command_match.group(1)
+
+                # Check for commands requiring blank lines before them, if they
+                # aren't at the start of a block.
+                if (
+                    command in WHITESPACE_BEFORE_SET
+                    and previous_indentation_level is not None
+                    and indentation_level == previous_indentation_level
+                    and previous_line_blank is False
+                ):
+                    yield (
+                        line_number,
+                        'Blank line required before `%s`' % (command,)
+                    )
+
+                # Check for commands where we shouldn't have blank lines before
+                # them, like `else` or the end of blocks like `endfunction`.
+                if (
+                    command in WHITESPACE_FORBIDDEN_BEFORE_SET
+                    and previous_line_blank is True
+                ):
+                    yield (
+                        line_number - 1,
+                        'Blank line forbidden before `%s`' % (command,)
+                    )
+
+                # Check for commands requiring blank lines after them, if they
+                # aren't at the end of a block.
+                if (
+                    previous_command is not None
+                    and previous_command in WHITESPACE_AFTER_SET
+                    and previous_indentation_level is not None
+                    and indentation_level == previous_indentation_level
+                    and previous_line_blank is False
+                ):
+                    yield (
+                        line_number - 1,
+                        'Blank line required after `%s`' % (command,)
+                    )
+
+                previous_command = command
+                previous_line_blank = False
+                previous_indentation_level = indentation_level
+
+
+def main():
+    status = 0
+
+    for filename in sys.argv[1:]:
+        with open(filename) as vim_file:
+            line_iter = (line.rstrip() for line in vim_file)
+
+            for line_number, message in check_lines(line_iter):
+                print('%s:%d %s' % (filename, line_number, message))
+                status = 1
+
+    sys.exit(status)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/test/script/custom-linting-rules b/test/script/custom-linting-rules
index 7aafe995..77e87db4 100755
--- a/test/script/custom-linting-rules
+++ b/test/script/custom-linting-rules
@@ -60,10 +60,10 @@ check_errors() {
 
     for directory in "${directories[@]}"; do
         # shellcheck disable=SC2086
-        while IFS= read -r match; do
+        while read -r; do
             RETURN_CODE=1
-            echo "$match $message"
-        done < <(grep -n "$regex" $include_arg "$directory"/**/*.vim \
+            echo "$REPLY $message"
+        done < <(grep -H -n "$regex" $include_arg "$directory"/**/*.vim \
             | grep -v 'no-custom-checks' \
             | grep -o '^[^:]\+:[0-9]\+' \
             | sed 's:^\./::')
@@ -126,4 +126,13 @@ check_errors '\(!=.\?\|isnot\) type(\[\])' "Use 'isnot v:t_list' instead"
 check_errors '\(!=.\?\|isnot\) type({})' "Use 'isnot v:t_dict' instead"
 check_errors '\(!=.\?\|isnot\) type(function([^)]\+))' "Use 'isnot v:t_func' instead"
 
+# Run a Python script to find lines that require padding around them.  For
+# users without Python installed, we'll skip these checks. Travis CI will run
+# the script.
+if command -v python > /dev/null; then
+    if ! test/script/block-padding-checker "$directory"/**/*.vim; then
+        RETURN_CODE=1
+    fi
+fi
+
 exit $RETURN_CODE