Merge pull request #6493 from wxtim/lint.6456.fewer_line_continuations

`cylc lint`: S015/U017 line continuation chars

changes.d/6459.feat.md

@@ -0,0 +1 @@
+`cylc lint` now checks for unnecessary continuation characters in the graph section.

cylc/flow/scripts/lint.py

@@ -617,7 +617,13 @@ def list_wrapper(line: str, check: Callable) -> Optional[Dict[str, str]]:
             for job_runner, directive in WALLCLOCK_DIRECTIVES.items()
         )),
         FUNCTION: check_wallclock_directives,
-    }
+    },
+    'S015': {
+        'short': (
+            '`=>` implies line continuation without `\\`.'
+        ),
+        FUNCTION: re.compile(r'=>\s*\\').findall
+    },
 }
 # Subset of deprecations which are tricky (impossible?) to scrape from the
 # upgrader.
@@ -785,6 +791,12 @@ def list_wrapper(line: str, check: Callable) -> Optional[Dict[str, str]]:
         FUNCTION: functools.partial(
             list_wrapper, check=CHECK_FOR_OLD_VARS.findall),
     },
+    'U017': {
+        'short': (
+            '`&` and `|` imply line continuation without `\\`'
+        ),
+        FUNCTION: re.compile(r'[&|]\s*\\').findall
+    },
 }
 ALL_RULESETS = ['728', 'style', 'all']
 EXTRA_TOML_VALIDATION = {

tests/unit/scripts/test_lint.py

@@ -45,7 +45,7 @@
 STYLE_CHECKS = parse_checks(['style'])
 UPG_CHECKS = parse_checks(['728'])
 
-TEST_FILE = """
+TEST_FILE = '''
 [visualization]
 
 [cylc]
@@ -98,7 +98,13 @@
     hold after point = 20220101T0000Z
     [[dependencies]]
         [[[R1]]]
-            graph = MyFaM:finish-all => remote => !mash_theme
+            graph = """
+                MyFaM:finish-all => remote => !mash_theme
+                a & \\
+                b => c
+                c | \\
+                d => e
+            """
 
 [runtime]
     [[root]]
@@ -155,10 +161,10 @@
             host = `rose host-select thingy`
 
 %include foo.cylc
-"""
+'''
 
 
-LINT_TEST_FILE = """
+LINT_TEST_FILE = '''
 \t[scheduler]
 
  [scheduler]
@@ -168,6 +174,11 @@
 {% foo %}
 {{foo}}
 # {{quix}}
+    R1 = """
+        foo & \\
+        bar => \\
+        baz
+    """
 
 [runtime]
     [[this_is_ok]]
@@ -183,7 +194,7 @@
                 -l walltime = 666
     [[baz]]
         platform = `no backticks`
-""" + (
+''' + (
     '\nscript = the quick brown fox jumps over the lazy dog until it becomes '
     'clear that this line is longer than the default 130 character limit.'
 )