[Qemu-devel] [PATCH v7 38/39] qapi: Support (subset of) \u escapes in strings

[Eric Blake <eblake@redhat.com>]

The handling of \ inside QAPI strings was less than ideal, and
really only worked JSON's \/, \\, \", and our extension of \'
(an obvious extension, when you realize we use '' instead of ""
for strings).  For other things, like '\n', it resulted in a
literal 'n' instead of a newline.

Of course, at the moment, we really have no use for escaped
characters, as QAPI has to map to C identifiers, and we currently
support ASCII only for that.  But down the road, we may add
support for default values for string parameters to a command
or struct; if that happens, it would be nice to correctly support
all JSON escape sequences, such as \n or \uXXXX.  This gets us
closer, by supporting Unicode escapes in the ASCII range.

Since JSON does not require \OCTAL or \xXX escapes, and our QMP
implementation does not understand them either, I intentionally
reject it here, but it would be an easy addition if we desired it.
Likewise, intentionally refusing the NUL byte means we don't have
to worry about C strings being shorter than the qapi input.

Signed-off-by: Eric Blake <eblake@redhat.com>

---

v7: add escape-outside-string, unknown-escape, and tighten parser
to reject unknown escapes and \u0000
---
 scripts/qapi.py                              | 36 +++++++++++++++++++++++++++-
 tests/Makefile                               |  2 ++
 tests/qapi-schema/escape-outside-string.err  |  1 +
 tests/qapi-schema/escape-outside-string.exit |  1 +
 tests/qapi-schema/escape-outside-string.json |  3 +++
 tests/qapi-schema/escape-outside-string.out  |  0
 tests/qapi-schema/escape-too-big.err         |  1 +
 tests/qapi-schema/escape-too-big.exit        |  1 +
 tests/qapi-schema/escape-too-big.json        |  3 +++
 tests/qapi-schema/escape-too-big.out         |  0
 tests/qapi-schema/escape-too-short.err       |  1 +
 tests/qapi-schema/escape-too-short.exit      |  1 +
 tests/qapi-schema/escape-too-short.json      |  3 +++
 tests/qapi-schema/escape-too-short.out       |  0
 tests/qapi-schema/ident-with-escape.err      |  1 -
 tests/qapi-schema/ident-with-escape.exit     |  2 +-
 tests/qapi-schema/ident-with-escape.json     |  2 +-
 tests/qapi-schema/ident-with-escape.out      |  3 +++
 tests/qapi-schema/unicode-str.err            |  1 +
 tests/qapi-schema/unicode-str.exit           |  1 +
 tests/qapi-schema/unicode-str.json           |  2 ++
 tests/qapi-schema/unicode-str.out            |  0
 tests/qapi-schema/unknown-escape.err         |  1 +
 tests/qapi-schema/unknown-escape.exit        |  1 +
 tests/qapi-schema/unknown-escape.json        |  3 +++
 tests/qapi-schema/unknown-escape.out         |  0
 26 files changed, 66 insertions(+), 4 deletions(-)
 create mode 100644 tests/qapi-schema/escape-outside-string.err
 create mode 100644 tests/qapi-schema/escape-outside-string.exit
 create mode 100644 tests/qapi-schema/escape-outside-string.json
 create mode 100644 tests/qapi-schema/escape-outside-string.out
 create mode 100644 tests/qapi-schema/escape-too-big.err
 create mode 100644 tests/qapi-schema/escape-too-big.exit
 create mode 100644 tests/qapi-schema/escape-too-big.json
 create mode 100644 tests/qapi-schema/escape-too-big.out
 create mode 100644 tests/qapi-schema/escape-too-short.err
 create mode 100644 tests/qapi-schema/escape-too-short.exit
 create mode 100644 tests/qapi-schema/escape-too-short.json
 create mode 100644 tests/qapi-schema/escape-too-short.out
 create mode 100644 tests/qapi-schema/unicode-str.err
 create mode 100644 tests/qapi-schema/unicode-str.exit
 create mode 100644 tests/qapi-schema/unicode-str.json
 create mode 100644 tests/qapi-schema/unicode-str.out
 create mode 100644 tests/qapi-schema/unknown-escape.err
 create mode 100644 tests/qapi-schema/unknown-escape.exit
 create mode 100644 tests/qapi-schema/unknown-escape.json
 create mode 100644 tests/qapi-schema/unknown-escape.out

diff --git a/scripts/qapi.py b/scripts/qapi.py
index 91c39d2..6f7ff0e 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -173,7 +173,41 @@ class QAPISchema:
                         raise QAPISchemaError(self,
                                               'Missing terminating "\'"')
                     if esc:
-                        string += ch
+                        if ch == 'b':
+                            string += '\b'
+                        elif ch == 'f':
+                            string += '\f'
+                        elif ch == 'n':
+                            string += '\n'
+                        elif ch == 'r':
+                            string += '\r'
+                        elif ch == 't':
+                            string += '\t'
+                        elif ch == 'u':
+                            value = 0
+                            for x in range(0, 4):
+                                ch = self.src[self.cursor]
+                                self.cursor += 1
+                                if ch not in "0123456789abcdefABCDEF":
+                                    raise QAPISchemaError(self,
+                                                          '\\u escape needs 4 '
+                                                          'hex digits')
+                                value = (value << 4) + int(ch, 16)
+                            # If Python 2 and 3 didn't disagree so much on
+                            # how to handle Unicode, then we could allow
+                            # Unicode string defaults.  But most of QAPI is
+                            # ASCII-only, so we aren't losing much for now.
+                            if not value or value > 0x7f:
+                                raise QAPISchemaError(self,
+                                                      'For now, \\u escape '
+                                                      'only supports non-zero '
+                                                      'values up to \\u007f')
+                            string += chr(value)
+                        elif ch in "\\/'\"":
+                            string += ch
+                        else:
+                            raise QAPISchemaError(self,
+                                                  "Unknown escape \\%s" %ch)
                         esc = False
                     elif ch == "\\":
                         esc = True
diff --git a/tests/Makefile b/tests/Makefile
index 45c205e..57d8987 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -212,6 +212,8 @@ check-qapi-schema-y := $(addprefix tests/qapi-schema/, \
 	enum-clash-member.json enum-max-member.json enum-union-clash.json \
 	enum-bad-name.json funny-char.json indented-expr.json \
 	missing-type.json bad-ident.json ident-with-escape.json \
+	escape-outside-string.json unknown-escape.json \
+	escape-too-short.json escape-too-big.json unicode-str.json \
 	double-type.json bad-base.json bad-type-bool.json bad-type-int.json \
 	bad-type-dict.json double-data.json unknown-expr-key.json \
 	redefined-type.json redefined-command.json redefined-builtin.json \
diff --git a/tests/qapi-schema/escape-outside-string.err b/tests/qapi-schema/escape-outside-string.err
new file mode 100644
index 0000000..b9b8837
--- /dev/null
+++ b/tests/qapi-schema/escape-outside-string.err
@@ -0,0 +1 @@
+tests/qapi-schema/escape-outside-string.json:3:27: Stray "\"
diff --git a/tests/qapi-schema/escape-outside-string.exit b/tests/qapi-schema/escape-outside-string.exit
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/tests/qapi-schema/escape-outside-string.exit
@@ -0,0 +1 @@
+1
diff --git a/tests/qapi-schema/escape-outside-string.json b/tests/qapi-schema/escape-outside-string.json
new file mode 100644
index 0000000..482f795
--- /dev/null
+++ b/tests/qapi-schema/escape-outside-string.json
@@ -0,0 +1,3 @@
+# escape sequences are permitted only inside strings
+# { 'command': 'foo', 'data': {} }
+{ 'command': 'foo', 'data'\u003a{} }
diff --git a/tests/qapi-schema/escape-outside-string.out b/tests/qapi-schema/escape-outside-string.out
new file mode 100644
index 0000000..e69de29
diff --git a/tests/qapi-schema/escape-too-big.err b/tests/qapi-schema/escape-too-big.err
new file mode 100644
index 0000000..d9aeb5d
--- /dev/null
+++ b/tests/qapi-schema/escape-too-big.err
@@ -0,0 +1 @@
+tests/qapi-schema/escape-too-big.json:3:14: For now, \u escape only supports non-zero values up to \u007f
diff --git a/tests/qapi-schema/escape-too-big.exit b/tests/qapi-schema/escape-too-big.exit
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/tests/qapi-schema/escape-too-big.exit
@@ -0,0 +1 @@
+1
diff --git a/tests/qapi-schema/escape-too-big.json b/tests/qapi-schema/escape-too-big.json
new file mode 100644
index 0000000..62bcecd
--- /dev/null
+++ b/tests/qapi-schema/escape-too-big.json
@@ -0,0 +1,3 @@
+# we don't support full Unicode strings, yet
+# { 'command': 'é' }
+{ 'command': '\u00e9' }
diff --git a/tests/qapi-schema/escape-too-big.out b/tests/qapi-schema/escape-too-big.out
new file mode 100644
index 0000000..e69de29
diff --git a/tests/qapi-schema/escape-too-short.err b/tests/qapi-schema/escape-too-short.err
new file mode 100644
index 0000000..934de59
--- /dev/null
+++ b/tests/qapi-schema/escape-too-short.err
@@ -0,0 +1 @@
+tests/qapi-schema/escape-too-short.json:3:14: \u escape needs 4 hex digits
diff --git a/tests/qapi-schema/escape-too-short.exit b/tests/qapi-schema/escape-too-short.exit
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/tests/qapi-schema/escape-too-short.exit
@@ -0,0 +1 @@
+1
diff --git a/tests/qapi-schema/escape-too-short.json b/tests/qapi-schema/escape-too-short.json
new file mode 100644
index 0000000..6cb1dec
--- /dev/null
+++ b/tests/qapi-schema/escape-too-short.json
@@ -0,0 +1,3 @@
+# the \u escape requires 4 hex digits
+# { 'command': 'a' }
+{ 'command': '\u61' }
diff --git a/tests/qapi-schema/escape-too-short.out b/tests/qapi-schema/escape-too-short.out
new file mode 100644
index 0000000..e69de29
diff --git a/tests/qapi-schema/ident-with-escape.err b/tests/qapi-schema/ident-with-escape.err
index f7d1c55..e69de29 100644
--- a/tests/qapi-schema/ident-with-escape.err
+++ b/tests/qapi-schema/ident-with-escape.err
@@ -1 +0,0 @@
-tests/qapi-schema/ident-with-escape.json:3: Expression is missing metatype
diff --git a/tests/qapi-schema/ident-with-escape.exit b/tests/qapi-schema/ident-with-escape.exit
index d00491f..573541a 100644
--- a/tests/qapi-schema/ident-with-escape.exit
+++ b/tests/qapi-schema/ident-with-escape.exit
@@ -1 +1 @@
-1
+0
diff --git a/tests/qapi-schema/ident-with-escape.json b/tests/qapi-schema/ident-with-escape.json
index cfb2050..5661750 100644
--- a/tests/qapi-schema/ident-with-escape.json
+++ b/tests/qapi-schema/ident-with-escape.json
@@ -1,4 +1,4 @@
-# FIXME: we should allow escape sequences in strings, if they map back to ASCII
+# we allow escape sequences in strings, if they map back to ASCII
 # { 'command': 'fooA', 'data': { 'bar1': 'str' } }
 { 'c\u006fmmand': '\u0066\u006f\u006FA',
   'd\u0061ta': { '\u0062\u0061\u00721': '\u0073\u0074\u0072' } }
diff --git a/tests/qapi-schema/ident-with-escape.out b/tests/qapi-schema/ident-with-escape.out
index e69de29..4028430 100644
--- a/tests/qapi-schema/ident-with-escape.out
+++ b/tests/qapi-schema/ident-with-escape.out
@@ -0,0 +1,3 @@
+[OrderedDict([('command', 'fooA'), ('data', OrderedDict([('bar1', 'str')]))])]
+[]
+[]
diff --git a/tests/qapi-schema/unicode-str.err b/tests/qapi-schema/unicode-str.err
new file mode 100644
index 0000000..f621cd6
--- /dev/null
+++ b/tests/qapi-schema/unicode-str.err
@@ -0,0 +1 @@
+tests/qapi-schema/unicode-str.json:2: 'command' uses invalid name 'é'
diff --git a/tests/qapi-schema/unicode-str.exit b/tests/qapi-schema/unicode-str.exit
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/tests/qapi-schema/unicode-str.exit
@@ -0,0 +1 @@
+1
diff --git a/tests/qapi-schema/unicode-str.json b/tests/qapi-schema/unicode-str.json
new file mode 100644
index 0000000..5253a1b
--- /dev/null
+++ b/tests/qapi-schema/unicode-str.json
@@ -0,0 +1,2 @@
+# we don't support full Unicode strings, yet
+{ 'command': 'é' }
diff --git a/tests/qapi-schema/unicode-str.out b/tests/qapi-schema/unicode-str.out
new file mode 100644
index 0000000..e69de29
diff --git a/tests/qapi-schema/unknown-escape.err b/tests/qapi-schema/unknown-escape.err
new file mode 100644
index 0000000..000e30d
--- /dev/null
+++ b/tests/qapi-schema/unknown-escape.err
@@ -0,0 +1 @@
+tests/qapi-schema/unknown-escape.json:3:21: Unknown escape \x
diff --git a/tests/qapi-schema/unknown-escape.exit b/tests/qapi-schema/unknown-escape.exit
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/tests/qapi-schema/unknown-escape.exit
@@ -0,0 +1 @@
+1
diff --git a/tests/qapi-schema/unknown-escape.json b/tests/qapi-schema/unknown-escape.json
new file mode 100644
index 0000000..8e6891e
--- /dev/null
+++ b/tests/qapi-schema/unknown-escape.json
@@ -0,0 +1,3 @@
+# we only recognize JSON escape sequences, plus our \' extension (no \x)
+# { 'command': 'foo', 'data': {} }
+{ 'command': 'foo', 'dat\x61':{} }
diff --git a/tests/qapi-schema/unknown-escape.out b/tests/qapi-schema/unknown-escape.out
new file mode 100644
index 0000000..e69de29
-- 
2.1.0