update_lints: add a check mode for travis runs

.travis.yml

@@ -3,5 +3,6 @@ rust: nightly
 sudo: false
 
 script:
+ - python util/update_lints.py -c
  - cargo build
  - cargo test

README.md

@@ -38,8 +38,8 @@ redundant_closure    | warn    | using redundant closures, i.e. `|a| foo(a)` (wh
 result_unwrap_used   | allow   | using `Result.unwrap()`, which might be better handled
 single_match         | warn    | a match statement with a single nontrivial arm (i.e, where the other arm is `_ => {}`) is used; recommends `if let` instead
 str_to_string        | warn    | using `to_string()` on a str, which should be `to_owned()`
-string_add           | allow   | using `x = x + ..` where x is a `String`; suggests using `push_str()` instead
-string_add_assign    | allow   | expressions of the form `x = x + ..` where x is a `String`
+string_add           | allow   | using `x + ..` where x is a `String`; suggests using `push_str()` instead
+string_add_assign    | allow   | using `x = x + ..` where x is a `String`; suggests using `push_str()` instead
 string_to_string     | warn    | calling `String.to_string()` which is a no-op
 toplevel_ref_arg     | warn    | a function argument is declared `ref` (i.e. `fn foo(ref x: u8)`, but not `fn foo((ref x, ref y): (u8, u8))`)
 zero_width_space     | deny    | using a zero-width space in a string literal, which is confusing

src/strings.rs

@@ -14,13 +14,13 @@ use utils::{match_def_path, span_lint, walk_ptrs_ty, get_parent_expr};
 declare_lint! {
     pub STRING_ADD_ASSIGN,
     Allow,
-    "expressions of the form `x = x + ..` where x is a `String`"
+    "using `x = x + ..` where x is a `String`; suggests using `push_str()` instead"
 }
 
 declare_lint! {
     pub STRING_ADD,
     Allow,
-    "using `x = x + ..` where x is a `String`; suggests using `push_str()` instead"
+    "using `x + ..` where x is a `String`; suggests using `push_str()` instead"
 }
 
 #[derive(Copy, Clone)]
@@ -48,13 +48,13 @@ impl LintPass for StringAdd {
                 //TODO check for duplicates
                  span_lint(cx, STRING_ADD, e.span,
                         "you added something to a string. \
-                        Consider using `String::push_str()` instead.")
+                         Consider using `String::push_str()` instead")
             }
         } else if let &ExprAssign(ref target, ref  src) = &e.node {
             if is_string(cx, target) && is_add(src, target) {
                 span_lint(cx, STRING_ADD_ASSIGN, e.span,
                     "you assigned the result of adding something to this string. \
-                    Consider using `String::push_str()` instead.")
+                     Consider using `String::push_str()` instead")
             }
         }
     }

util/update_lints.py

@@ -1,5 +1,7 @@
+#!/usr/bin/env python
 # Generate a Markdown table of all lints, and put it in README.md.
 # With -n option, only print the new table to stdout.
+# With -c option, print a warning and set exit status to 1 if a file would be changed.
 
 import os
 import re
@@ -31,27 +33,27 @@ def collect(lints, fn):
                       desc.replace('\\"', '"')))
 
 
-def write_tbl(lints, fp):
+def gen_table(lints):
     """Write lint table in Markdown format."""
     # first and third column widths
     w_name = max(len(l[1]) for l in lints)
     w_desc = max(len(l[3]) for l in lints)
     # header and underline
-    fp.write('%-*s | default | meaning\n' % (w_name, 'name'))
-    fp.write('%s-|-%s-|-%s\n' % ('-' * w_name, '-' * 7, '-' * w_desc))
+    yield '%-*s | default | meaning\n' % (w_name, 'name')
+    yield '%s-|-%s-|-%s\n' % ('-' * w_name, '-' * 7, '-' * w_desc)
     # one table row per lint
     for (_, name, default, meaning) in sorted(lints, key=lambda l: l[1]):
-        fp.write('%-*s | %-7s | %s\n' % (w_name, name, default, meaning))
+        yield '%-*s | %-7s | %s\n' % (w_name, name, default, meaning)
 
 
-def write_group(lints, fp):
+def gen_group(lints):
     """Write lint group (list of all lints in the form module::NAME)."""
     for (module, name, _, _) in sorted(lints):
-        fp.write('        %s::%s,\n' % (module, name.upper()))
+        yield '        %s::%s,\n' % (module, name.upper())
 
 
 def replace_region(fn, region_start, region_end, callback,
-                   replace_start=True):
+                   replace_start=True, write_back=True):
     """Replace a region in a file delimited by two lines matching regexes.
 
     A callback is called to write the new region.  If `replace_start` is true,
@@ -63,24 +65,32 @@ def replace_region(fn, region_start, region_end, callback,
         lines = list(fp)
 
     # replace old region with new region
-    with open(fn, 'w') as fp:
-        in_old_region = False
-        for line in lines:
-            if in_old_region:
-                if re.search(region_end, line):
-                    in_old_region = False
-                    fp.write(line)
-            elif re.search(region_start, line):
-                if not replace_start:
-                    fp.write(line)
-                # old region starts here
-                in_old_region = True
-                callback(fp)
-            else:
-                fp.write(line)
+    new_lines = []
+    in_old_region = False
+    for line in lines:
+        if in_old_region:
+            if re.search(region_end, line):
+                in_old_region = False
+                new_lines.extend(callback())
+                new_lines.append(line)
+        elif re.search(region_start, line):
+            if not replace_start:
+                new_lines.append(line)
+            # old region starts here
+            in_old_region = True
+        else:
+            new_lines.append(line)
+
+    # write back to file
+    if write_back:
+        with open(fn, 'w') as fp:
+            fp.writelines(new_lines)
+
+    # if something changed, return true
+    return lines != new_lines
 
 
-def main(print_only=False):
+def main(print_only=False, check=False):
     lints = []
 
     # check directory
@@ -95,16 +105,23 @@ def main(print_only=False):
                 collect(lints, os.path.join(root, fn))
 
     if print_only:
-        write_tbl(lints, sys.stdout)
+        sys.stdout.writelines(gen_table(lints))
         return
 
     # replace table in README.md
-    replace_region('README.md', r'^name +\|', '^$', lambda fp: write_tbl(lints, fp))
+    changed = replace_region('README.md', r'^name +\|', '^$',
+                             lambda: gen_table(lints),
+                             write_back=not check)
 
     # same for "clippy" lint collection
-    replace_region('src/lib.rs', r'reg.register_lint_group\("clippy"', r'\]\);',
-                   lambda fp: write_group(lints, fp), replace_start=False)
+    changed |= replace_region('src/lib.rs', r'reg.register_lint_group\("clippy"', r'\]\);',
+                              lambda: gen_group(lints), replace_start=False,
+                              write_back=not check)
+
+    if check and changed:
+        print('Please run util/update_lints.py to regenerate lints lists.')
+        return 1
 
 
 if __name__ == '__main__':
-    main(print_only='-n' in sys.argv)
+    sys.exit(main(print_only='-n' in sys.argv, check='-c' in sys.argv))