Give intelligent warning messages on zero-length variable names.

darcs-hash:20051207130330-ac50b-cc9d78ba63f592925b6076049e2c59aaaa930eec.gz

4 files changed, 60 insertions, 7 deletions

diff --git a/doc_src/doc.hdr b/doc_src/doc.hdr
index cd42a2fc..d37ef744 100644
--- a/doc_src/doc.hdr
+++ b/doc_src/doc.hdr
@@ -323,7 +323,7 @@ undergoes the process of parameter expantion before it is sent on to
 the command.  There are many ways in which the user can specify a
 parameter to be expanded. These include:
 
-\subsection expand-wildcards Wildcards 
+\subsection expand-wildcard Wildcards 
 
 If a star (*) or a question mark (?) is present in the parameter, \c
 fish attempts to mach the given parameter to any files in such a
@@ -381,11 +381,31 @@ href="#variables"> Environment variables</a> section.
 Example:
 
 <tt> echo \$HOME</tt> prints the home directory of the current
-user. If you wish to combine environment variables with text, you can
+user. 
+
+If you wish to combine environment variables with text, you can
 encase the variables within braces to embed a variable inside running
 text like <tt>echo Konnichiwa {$USER}san</tt>, which will print a
 personalized Japanese greeting.
 
+The {$USER}san syntax might need a bit of an elaboration.  Posix
+shells allow you to specify a variable name using '$VARNAME' or
+'${VARNAME}'. Fish only supports the former, but has no support
+whatsoever for the latter or anything remotely like it. So what is
+'{$VARNAME}' then? Well, '{WHATEVER}' is <a href='#brace'>brace
+expantion</a>, the same as supported by Posix shells, i.e.  'a{b,c}d'
+-> 'abd acd' works both in bash and on fish. So '{$VARNAME}' is a
+bracket-expantion with only a single element, i.e.  it becomes
+expanded to '$VARNAME', which will be variable expanded to the value
+of the variable 'VARNAME'. So you might think that the brackets don't
+actually do anything, and that is nearly the truth. The snag is that
+there once along the way was a '}' in there somewhere, and } is not a
+valid character in a variable name.  So anything after the otherwise
+pointless bracket expantion becomes NOT a part of the variable name,
+even if it happens to be a legal variable name character. That's why
+'{$USER}san' works. A case of one syntax just lending itself so nicely
+to solving an unrelated problem in it's spare time.
+
 Variable expantion is the only type of expantion performed on double
 quoted strings. There is, however, an important difference in how
 variables are expanded when quoted and when unquoted. An unquoted
@@ -398,6 +418,7 @@ result in exactly one argument. Undefined variables will expand to the
 empty string, and array variables will be concatenated using the space
 character.
 
+
 \subsection expand-home Home directory expansion
 
 The ~ (tilde) character at the beginning of a parameter, followed by a
@@ -504,12 +525,12 @@ Example:
 
 The following code will not output anything:
 <pre>
-if true
+begin
 	# This is a nice local scope where all variables will die
 	set -l pirate 'There be treasure in them thar hills'
 end
 
-# This will not output anything, since the pirate is dead
+# This will not output anything, since the pirate was local
 echo $pirate
 </pre>
 
diff --git a/expand.c b/expand.c
index 4b8e1e14..941ed6f9 100644
--- a/expand.c
+++ b/expand.c
@@ -67,6 +67,9 @@ parameter expansion.
 */
 #define COMPLETE_LAST_DESC COMPLETE_SEP_STR L"Last background job"
 
+#define COMPLETE_VAR_DESC L"Variable name is zero characters long."
+#define COMPLETE_VAR2_DESC L" Did you mean {$VARIABLE}? For information on how variable expantion in fish differs from Posix variable expantion, see the manual section on variable expantion by typing 'help expand-variable'."
+
 /**
    String in process expansion denoting ourself
 */
@@ -727,6 +730,28 @@ static int expand_variables( wchar_t *in, array_list_t *out )
 /*			printf( "Stop for '%c'\n", in[stop_pos]);*/
 			
 			var_len = stop_pos - start_pos;
+
+			if( var_len == 0 )
+			{
+				if( in[stop_pos] == BRACKET_BEGIN )
+				{
+										
+					error( SYNTAX_ERROR,
+						   COMPLETE_VAR_DESC
+						   COMPLETE_VAR2_DESC ,
+						   -1 );
+				}
+				else
+				{
+					error( SYNTAX_ERROR,
+						   COMPLETE_VAR_DESC,
+						   -1 );
+				}
+				
+				is_ok = 0;
+				break;
+			}
+			
 			
 			if( !(var_name = malloc( sizeof(wchar_t)*(var_len+1) )))
 			{
diff --git a/init/completions/help.fish b/init/completions/help.fish
index 4dd2f46f..6f20fcd1 100644
--- a/init/completions/help.fish
+++ b/init/completions/help.fish
@@ -22,7 +22,6 @@ complete -c help -x -a prompt -d "Help on how to set the prompt"
 complete -c help -x -a title -d "Help on how to set the titlebar message"
 complete -c help -x -a killring -d "Help on how to copy and paste"
 complete -c help -x -a editor -d "Help on editor shortcuts"
-complete -c help -x -a expand -d "Help on parameter expantion (Globbing)"
 complete -c help -x -a globbing -d "Help on parameter expantion (Globbing)"
 complete -c help -x -a variables -d "Help on environment variables"
 complete -c help -x -a color -d "Help on setting syntax highlighting colors"
@@ -31,3 +30,10 @@ complete -c help -x -a title -d "Help on changing the titlebar messages"
 complete -c help -x -a builtin-overview -d "A short summary of all builtin commands"
 complete -c help -x -a changes -d "The changelog"
 
+complete -c help -x -a expand -d "Help on parameter expantion (Globbing)"
+complete -c help -x -a expand-variable -d "Help on variable exapantion \$VARNAME"
+complete -c help -x -a expand-home -d "Help on home directory expantion ~USER"
+complete -c help -x -a expand-brace -d "Help on brace expantion {a,b,c}"
+complete -c help -x -a expand-wildcard -d "Help on wildcard expantion *.*"
+complete -c help -x -a expand-command-substitution -d "Help on command substututions (SUBCOMMAND)"
+complete -c help -x -a expand-process -d "Help on process expantion %JOB"
diff --git a/init/fish_function.fish b/init/fish_function.fish
index dc805449..009221ea 100644
--- a/init/fish_function.fish
+++ b/init/fish_function.fish
@@ -158,8 +158,9 @@ function help -d "Show help for the fish shell"
 	end
 	
 	set idx_subj syntax completion editor job-control todo bugs history
-	set idx_subj $idx_subj killring help color prompt title expand variables
-	set idx_subj $idx_subj builtin-overview changes
+	set idx_subj $idx_subj killring help color prompt title variables
+	set idx_subj $idx_subj builtin-overview changes 
+	set idx_subj $idx_subj expand expand-variable expand-home expand-brace expand-wildcard expand-command-substitution expand-process 
 
 	if contains -- $fish_help_item $idx_subj
 		set fish_help_page "index.html\#"$fish_help_item