Merge branch 'raimo/triple-quoted-strings-warning' OTP-18821 into maint

RaimoNiskanen · RaimoNiskanen · commit d6b2f3bd1ce0 · 2023-11-10T11:11:33.000+01:00
* raimo/triple-quoted-strings-warning:
  Fix OTP test suite
  Implement warning for adjacent string literals without intervening white space
diff --git a/bootstrap/lib/stdlib/ebin/edlin_key.beam b/bootstrap/lib/stdlib/ebin/edlin_key.beam
diff --git a/bootstrap/lib/stdlib/ebin/epp.beam b/bootstrap/lib/stdlib/ebin/epp.beam
diff --git a/lib/kernel/test/prim_file_SUITE.erl b/lib/kernel/test/prim_file_SUITE.erl
@@ -710,7 +710,7 @@ file_info_basic_file(Config) when is_list(Config) ->
     %% Create a short file.
     Name = filename:join(RootDir,
 			 atom_to_list(?MODULE)
-			 ++"_basic_test"".fil"),
+			 ++"_basic_test.fil"),
     {ok,Fd1} = ?PRIM_FILE:open(Name, [write]),
     ?PRIM_FILE:write(Fd1, "foo bar"),
     ok = ?PRIM_FILE:close(Fd1),
diff --git a/lib/stdlib/src/epp.erl b/lib/stdlib/src/epp.erl
@@ -251,7 +251,12 @@ format_error({warning,Term}) ->
 format_error(ftr_after_prefix) ->
     "feature directive not allowed after exports or record definitions";
 format_error(tqstring) ->
-    "Triple-quoted (or more) strings will change meaning in OTP-27.0";
+    "triple-quoted (or more) strings will change meaning in OTP-27.0";
+format_error(string_concat) ->
+    "adjacent string literals without intervening white space\n"
+        "In OTP-27.0 this will be a triple-quoted string or an error.\n"
+        "Rewrite them as one string, or insert white space\n"
+        "between the strings.";
 format_error(E) -> file:format_error(E).
 
 -spec scan_file(FileName, Options) ->
@@ -352,9 +357,10 @@ parse_file(Epp) ->
     case epp_request(Epp, scan_erl_form) of
 	{ok,Toks} ->
             Warnings =
-                [{warning, {erl_anno:location(Anno),?MODULE,tqstring}}
-                 %% Warn about using 3 or more double qoutes
-                 || {tqstring,Anno,_} <- Toks],
+                [{warning, {erl_anno:location(Anno),?MODULE,Tag}}
+                 || {Tag,Anno,_} <- Toks,
+                    %% Warn for string concatenation without white space
+                    Tag =:= string_concat],
             case erl_parse:parse_form(Toks) of
                 {ok, Form} ->
                     [Form|Warnings] ++ parse_file(Epp);
diff --git a/lib/stdlib/src/erl_parse.yrl b/lib/stdlib/src/erl_parse.yrl
@@ -77,7 +77,7 @@ ssa_check_when_clause
 ssa_check_when_clauses.
 
 Terminals
-char integer float atom tqstring string var
+char integer float atom string string_concat var
 
 '(' ')' ',' '->' '{' '}' '[' ']' '|' '||' '<-' ';' ':' '#' '.'
 'after' 'begin' 'case' 'try' 'catch' 'end' 'fun' 'if' 'of' 'receive' 'when'
@@ -546,11 +546,11 @@ atomic -> atom : '$1'.
 atomic -> strings : '$1'.
 
 strings -> string : '$1'.
-strings -> tqstring : {string,?anno('$1'),element(3, '$1')}.
+strings -> string string_concat : '$1'.
 strings -> string strings :
 	{string,?anno('$1'),element(3, '$1') ++ element(3, '$2')}.
-strings -> tqstring strings :
-	{string,?anno('$1'),element(3, '$1') ++ element(3, '$2')}.
+strings -> string string_concat strings :
+	{string,?anno('$1'),element(3, '$1') ++ element(3, '$3')}.
 
 prefix_op -> '+' : '$1'.
 prefix_op -> '-' : '$1'.
diff --git a/lib/stdlib/src/erl_scan.erl b/lib/stdlib/src/erl_scan.erl
@@ -425,12 +425,6 @@ scan1("."=Cs, St, Line, Col, Toks) ->
     {more,{Cs,St,Col,Toks,Line,[],fun scan/6}};
 scan1([$.=C|Cs], St, Line, Col, Toks) ->
     scan_dot(Cs, St, Line, Col, Toks, [C]);
-scan1([$",$",$"|Cs], St, Line, Col, Toks) -> %" Emacs
-    scan_tqstring(Cs, St, Line, Col, Toks, 3); % Number of quote chars
-scan1([$",$"]=Cs, St, Line, Col, Toks) ->
-    {more,{Cs,St,Col,Toks,Line,[],fun scan/6}};
-scan1([$"]=Cs, St, Line, Col, Toks) -> %" Emacs
-    {more,{Cs,St,Col,Toks,Line,[],fun scan/6}};
 scan1([$"|Cs], St, Line, Col, Toks) -> %" Emacs
     State0 = {[],[],Line,Col},
     scan_string(Cs, St, Line, incr_column(Col, 1), Toks, State0);
@@ -834,31 +828,6 @@ scan_char([], St, Line, Col, Toks) ->
 scan_char(eof, _St, Line, Col, _Toks) ->
     scan_error(char, Line, Col, Line, incr_column(Col, 1), eof).
 
-%% Scan leading $" characters until we have them all
-%%
-scan_tqstring(Cs, St, Line, Col, Toks, Qs) ->
-    case Cs of
-        [$"|Ncs] ->
-            scan_tqstring(Ncs, St, Line, Col, Toks, Qs+1);
-        [] ->
-            {more, {[], St, Col, Toks, Line, Qs, fun scan_tqstring/6}};
-        _ ->
-            scan_tqstring_finish(Cs, St, Line, Col, Toks, Qs, tqstring)
-    end.
-
-scan_tqstring_finish(Cs, St, Line, Col, Toks, Qs, TokTag) when 1 < Qs ->
-    Anno = anno(Line, Col, St, ?STR(string, St, [$",$"])),
-    Tok = {TokTag, Anno, ""},
-    scan_tqstring_finish(
-      Cs, St, Line, incr_column(Col, 2), [Tok|Toks], Qs-2, string);
-scan_tqstring_finish(Cs, St, Line, Col, Toks, Qs, _TokTag) ->
-    Ncs =
-        case Qs of
-            1 -> [$"|Cs];%"
-            0 -> Cs
-        end,
-    scan1(Ncs, St, Line, Col, Toks).
-
 scan_string(Cs, #erl_scan{}=St, Line, Col, Toks, {Wcs,Str,Line0,Col0}) ->
     case scan_string0(Cs, St, Line, Col, $\", Str, Wcs) of %"
         {more,Ncs,Nline,Ncol,Nstr,Nwcs} ->
@@ -871,7 +840,19 @@ scan_string(Cs, #erl_scan{}=St, Line, Col, Toks, {Wcs,Str,Line0,Col0}) ->
             scan_error({string,$\",Estr}, Line0, Col0, Nline, Ncol, Ncs); %"
         {Ncs,Nline,Ncol,Nstr,Nwcs} ->
             Anno = anno(Line0, Col0, St, ?STR(string, St, Nstr)),
-            scan1(Ncs, St, Nline, Ncol, [{string,Anno,Nwcs}|Toks])
+            scan_string_concat(
+              Ncs, St, Nline, Ncol, [{string,Anno,Nwcs}|Toks], [])
+        end.
+
+scan_string_concat(Cs, St, Line, Col, Toks, _) ->
+    case Cs of
+        [$"|_] ->
+            Anno = anno(Line, Col, St, ?STR(string, St, "")),
+            scan1(Cs, St, Line, Col, [{string_concat,Anno,""}|Toks]);
+        [] ->
+            {more,{Cs,St,Col,Toks,Line,[],fun scan_string_concat/6}};
+        _ ->
+            scan1(Cs, St, Line, Col, Toks)
     end.
 
 scan_qatom(Cs, #erl_scan{}=St, Line, Col, Toks, {Wcs,Str,Line0,Col0}) ->
diff --git a/lib/stdlib/test/epp_SUITE.erl b/lib/stdlib/test/epp_SUITE.erl
@@ -30,7 +30,7 @@
          otp_11728/1, encoding/1, extends/1,  function_macro/1,
 	 test_error/1, test_warning/1, otp_14285/1,
 	 test_if/1,source_name/1,otp_16978/1,otp_16824/1,scan_file/1,file_macro/1,
-         triple_quotes_warning/1,
+         string_concat_warning/1,
    deterministic_include/1, nondeterministic_include/1]).
 
 -export([epp_parse_erl_form/2]).
@@ -74,7 +74,7 @@ all() ->
      otp_8665, otp_8911, otp_10302, otp_10820, otp_11728,
      encoding, extends, function_macro, test_error, test_warning,
      otp_14285, test_if, source_name, otp_16978, otp_16824, scan_file, file_macro,
-     triple_quotes_warning,
+     string_concat_warning,
      deterministic_include, nondeterministic_include].
 
 groups() ->
@@ -937,6 +937,7 @@ scan_file(Config) when is_list(Config) ->
     [{'-',_}, {atom,_,export}, {'(',_} | _ ] = ExportForm,
     [{'-',_}, {atom,_,file}, {'(',_} | _ ] = FileForm2,
     [{'-',_}, {atom,_,file}, {'(',_} | _ ] = FileForm3,
+    [{atom,_,ok}, {'(',_} | _ ] = FunctionForm,
     ok.
 
 macs(Epp) ->
@@ -2057,73 +2058,98 @@ otp_16824(Config) when is_list(Config) ->
     [] = compile(Config, Cs),
     ok.
 
-triple_quotes_warning(Config) when is_list(Config) ->
+string_concat_warning(Config) when is_list(Config) ->
     Cs1 =
-        [{triple_quotes_warning_1,
+        [{string_concat_warning_1,
+          <<"\n"
+            "-export([foo/0]).\n"
+            "foo() ->\n"
+            "    \" \"\"\".\n">>,
+          {warnings,
+           [{{4,8},epp,string_concat}]}},
+        {string_concat_warning_2,
+          <<"\n"
+            "-export([foo/0]).\n"
+            "foo() ->\n"
+            "    \" \"\"\" \" \"\"\".\n">>,
+          {warnings,
+           [{{4,8},epp,string_concat},
+            {{4,14},epp,string_concat}]}}],
+    [] = compile(Config, Cs1),
+
+    Cs2 =
+        [{string_concat_warning_3,
           <<"\n-doc \"foo\".\n">>,
           []},
-         {triple_quotes_warning_2,
+         {string_concat_warning_4,
           <<"\n-doc \"\" \"foo\" \"\".\n">>,
           []},
-         {triple_quotes_warning_3,
+         {string_concat_warning_5,
           <<"\n"
             "-doc \"\"\"\n"
             "    foo\n"
             "    \"\"\".\n">>,
-          {warnings,[{{2,6},epp,tqstring}]}},
-         {triple_quotes_warning_4,
+          {warnings,
+           [{{2,8},epp,string_concat},
+            {{4,6},epp,string_concat}]}},
+         {string_concat_warning_6,
           <<"\n"
             "-doc  \"\"\"\"\n"
             "      \"\"\"\".\n">>,
           {warnings,
-           [{{2,7},epp,tqstring},
-            {{3,7},epp,tqstring}]}},
-         {triple_quotes_warning_5,
+           [{{2,9},epp,string_concat},
+            {{3,9},epp,string_concat}]}},
+         {string_concat_warning_7,
           <<"\n"
             "-doc   \"\"\"\"\"\n"
             "       foo\n"
             "       \"\"\"\"\".\n">>,
           {warnings,
-           [{{2,8},epp,tqstring},
-            {{4,9},epp,tqstring}]}}
+           [{{2,10},epp,string_concat},
+            {{2,12},epp,string_concat},
+            {{4,9},epp,string_concat},
+            {{4,11},epp,string_concat}]}}
         ],
-    [] = compile(Config, Cs1),
+    [] = compile(Config, Cs2),
 
-    Cs2 =
-        [{triple_quotes_warning_10,
+    Cs3 =
+        [{string_concat_warning_8,
           <<"\n"
             "-export([foo/0]).\n"
             "foo() ->\n"
             "    \"\"\"\n"
             "    bar\n"
             "    \"\"\".\n">>,
-          {warnings,[{{4,5},epp,tqstring}]}},
-         {triple_quotes_warning_11,
+          {warnings,
+           [{{4,7},epp,string_concat},
+            {{6,6},epp,string_concat}]}},
+         {string_concat_warning_9,
           <<"\n"
             "-export([foo/0]).\n"
             "foo() ->\n"
             "    \"\"\"\"\n"
             "    ++ lists:duplicate(4, $x) ++\n"
             "    \"\"\"\".\n">>,
           {warnings,
-           [{{4,5},epp,tqstring},
-            {{6,5},epp,tqstring}]}},
-         {triple_quotes_warning_12,
+           [{{4,7},epp,string_concat},
+            {{6,7},epp,string_concat}]}},
+         {string_concat_warning_10,
           <<"\n"
             "-export([foo/0]).\n"
             "foo() ->\n"
             "    \"\"\"\"\"\n"
             "    bar\n"
             "    \"\"\"\"\".\n">>,
           {warnings,
-           [{{4,5},epp,tqstring},
-            {{6,6},epp,tqstring}]}} ],
-    [] = compile(Config, Cs2),
+           [{{4,7},epp,string_concat},
+            {{4,9},epp,string_concat},
+            {{6,6},epp,string_concat},
+            {{6,8},epp,string_concat}]}} ],
+    [] = compile(Config, Cs3),
 
     ok.
 
 
-
 %% Start location is 1.
 check(Config, Tests) ->
     eval_tests(Config, fun check_test/3, Tests).
diff --git a/system/doc/general_info/upcoming_incompatibilities.xml b/system/doc/general_info/upcoming_incompatibilities.xml
@@ -278,15 +278,22 @@ String Content
 "++ foo() ++"
       </pre>
       <p>
-        From Erlang/OTP 26.1 up to 27.0 the compiler issues a warning for
-        a sequence of 3 or more double-quote characters
+        From Erlang/OTP 26.1 up to 26.2 the compiler issues a warning
+        for a sequence of 3 or more double-quote characters
         since that is almost certainly a mistake or
         something like a result of bad automatic code generation.
         If a users gets that warning, the code should be corrected
         for example by inserting appropriate spaces between
         the empty strings, or removing the redundant ones alltogether,
         which will have the same meaning before and after Erlang/OTP 27.
       </p>
+      <p>
+        From Erlang/OTP 26.2 up to 27.0 this is improved
+        so the compiler instead issues a warning for adjacent string literals
+        without intervening white space, which effectively is the same
+        at a string start, but also covers the same situation
+        at a string end.
+      </p>
     </section>
 
   </section>
