qapi: Drop support for escape sequences other than \\

Since the previous commit restricted strings to printable ASCII,
\uXXXX's only use is obfuscation.  Drop it.

This leaves \\, \/, \', and \".  Since QAPI schema strings are all
names, and names are restricted to ASCII letters, digits, hyphen, and
underscore, none of them is useful.

The latter three have no test coverage.  Drop them.

Keep \\ to avoid (more) gratuitous incompatibility with JSON.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190913201349.24332-8-armbru@redhat.com>

tests/qapi-schema/escape-outside-string.err

@@ -1 +0,0 @@
-tests/qapi-schema/escape-outside-string.json:3:27: Stray "\"

tests/qapi-schema/escape-outside-string.exit

@@ -1 +0,0 @@
-1

tests/qapi-schema/escape-outside-string.json

@@ -1,3 +0,0 @@
-# escape sequences are permitted only inside strings
-# { 'command': 'foo', 'data': {} }
-{ 'command': 'foo', 'data'\u003a{} }

tests/qapi-schema/escape-too-big.err

@@ -1 +0,0 @@
-tests/qapi-schema/escape-too-big.json:3:14: For now, \u escape only supports non-zero values up to \u007f

tests/qapi-schema/escape-too-big.exit

@@ -1 +0,0 @@
-1

tests/qapi-schema/escape-too-big.json

@@ -1,3 +0,0 @@
-# we don't support full Unicode strings, yet
-# { 'command': 'é' }
-{ 'command': '\u00e9' }

tests/qapi-schema/escape-too-short.err

@@ -1 +0,0 @@
-tests/qapi-schema/escape-too-short.json:3:14: \u escape needs 4 hex digits

tests/qapi-schema/escape-too-short.exit

@@ -1 +0,0 @@
-1

tests/qapi-schema/escape-too-short.json

@@ -1,3 +0,0 @@
-# the \u escape requires 4 hex digits
-# { 'command': 'a' }
-{ 'command': '\u61' }

tests/qapi-schema/ident-with-escape.err

@@ -0,0 +1 @@
+tests/qapi-schema/ident-with-escape.json:3:3: Unknown escape \u

tests/qapi-schema/ident-with-escape.exit

@@ -1 +1 @@
-0
+1

tests/qapi-schema/ident-with-escape.json

@@ -1,4 +1,4 @@
-# we allow escape sequences in strings, if they map back to ASCII
+# we don't recognize any \ escapes other than \\ (tested elsewhere)
 # { 'command': 'fooA', 'data': { 'bar1': 'str' } }
 { 'c\u006fmmand': '\u0066\u006f\u006FA',
   'd\u0061ta': { '\u0062\u0061\u00721': '\u0073\u0074\u0072' } }

tests/qapi-schema/ident-with-escape.out

@@ -1,16 +0,0 @@
-module None
-object q_empty
-enum QType
-    prefix QTYPE
-    member none
-    member qnull
-    member qnum
-    member qstring
-    member qdict
-    member qlist
-    member qbool
-module ident-with-escape.json
-object q_obj_fooA-arg
-    member bar1: str optional=False
-command fooA q_obj_fooA-arg -> None
-   gen=True success_response=True boxed=False oob=False preconfig=False

tests/qapi-schema/unknown-escape.json

@@ -1,3 +1,3 @@
-# we only recognize JSON escape sequences, plus our \' extension (no \x)
+# we only recognize \\
 # { 'command': 'foo', 'data': {} }
 { 'command': 'foo', 'dat\x61':{} }