Rename the xmpp-parsers directory to parsers

This doesn’t change anything to the name of the crate, just makes
autocompletion easier by not sharing the same prefix as the xmpp crate.

parsers/src/util/error.rs

@@ -0,0 +1,105 @@
+// Copyright (c) 2017-2018 Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+use std::error::Error as StdError;
+use std::fmt;
+
+/// Contains one of the potential errors triggered while parsing an
+/// [Element](../struct.Element.html) into a specialised struct.
+#[derive(Debug)]
+pub enum Error {
+    /// The usual error when parsing something.
+    ///
+    /// TODO: use a structured error so the user can report it better, instead
+    /// of a freeform string.
+    ParseError(&'static str),
+
+    /// Generated when some base64 content fails to decode, usually due to
+    /// extra characters.
+    Base64Error(base64::DecodeError),
+
+    /// Generated when text which should be an integer fails to parse.
+    ParseIntError(std::num::ParseIntError),
+
+    /// Generated when text which should be a string fails to parse.
+    ParseStringError(std::string::ParseError),
+
+    /// Generated when text which should be an IP address (IPv4 or IPv6) fails
+    /// to parse.
+    ParseAddrError(std::net::AddrParseError),
+
+    /// Generated when text which should be a [JID](../../jid/struct.Jid.html)
+    /// fails to parse.
+    JidParseError(jid::JidParseError),
+
+    /// Generated when text which should be a
+    /// [DateTime](../date/struct.DateTime.html) fails to parse.
+    ChronoParseError(chrono::ParseError),
+}
+
+impl StdError for Error {
+    fn cause(&self) -> Option<&dyn StdError> {
+        match self {
+            Error::ParseError(_) => None,
+            Error::Base64Error(e) => Some(e),
+            Error::ParseIntError(e) => Some(e),
+            Error::ParseStringError(e) => Some(e),
+            Error::ParseAddrError(e) => Some(e),
+            Error::JidParseError(e) => Some(e),
+            Error::ChronoParseError(e) => Some(e),
+        }
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Error::ParseError(s) => write!(fmt, "parse error: {}", s),
+            Error::Base64Error(e) => write!(fmt, "base64 error: {}", e),
+            Error::ParseIntError(e) => write!(fmt, "integer parsing error: {}", e),
+            Error::ParseStringError(e) => write!(fmt, "string parsing error: {}", e),
+            Error::ParseAddrError(e) => write!(fmt, "IP address parsing error: {}", e),
+            Error::JidParseError(e) => write!(fmt, "JID parsing error: {}", e),
+            Error::ChronoParseError(e) => write!(fmt, "time parsing error: {}", e),
+        }
+    }
+}
+
+impl From<base64::DecodeError> for Error {
+    fn from(err: base64::DecodeError) -> Error {
+        Error::Base64Error(err)
+    }
+}
+
+impl From<std::num::ParseIntError> for Error {
+    fn from(err: std::num::ParseIntError) -> Error {
+        Error::ParseIntError(err)
+    }
+}
+
+impl From<std::string::ParseError> for Error {
+    fn from(err: std::string::ParseError) -> Error {
+        Error::ParseStringError(err)
+    }
+}
+
+impl From<std::net::AddrParseError> for Error {
+    fn from(err: std::net::AddrParseError) -> Error {
+        Error::ParseAddrError(err)
+    }
+}
+
+impl From<jid::JidParseError> for Error {
+    fn from(err: jid::JidParseError) -> Error {
+        Error::JidParseError(err)
+    }
+}
+
+impl From<chrono::ParseError> for Error {
+    fn from(err: chrono::ParseError) -> Error {
+        Error::ChronoParseError(err)
+    }
+}

parsers/src/util/helpers.rs

@@ -0,0 +1,122 @@
+// Copyright (c) 2017 Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+use crate::util::error::Error;
+use jid::Jid;
+use std::str::FromStr;
+
+/// Codec for text content.
+pub struct Text;
+
+impl Text {
+    pub fn decode(s: &str) -> Result<String, Error> {
+        Ok(s.to_owned())
+    }
+
+    pub fn encode(string: &str) -> Option<String> {
+        Some(string.to_owned())
+    }
+}
+
+/// Codec for plain text content.
+pub struct PlainText;
+
+impl PlainText {
+    pub fn decode(s: &str) -> Result<Option<String>, Error> {
+        Ok(match s {
+            "" => None,
+            text => Some(text.to_owned()),
+        })
+    }
+
+    pub fn encode(string: &Option<String>) -> Option<String> {
+        string.as_ref().map(ToOwned::to_owned)
+    }
+}
+
+/// Codec for trimmed plain text content.
+pub struct TrimmedPlainText;
+
+impl TrimmedPlainText {
+    pub fn decode(s: &str) -> Result<String, Error> {
+        Ok(match s.trim() {
+            "" => return Err(Error::ParseError("URI missing in uri.")),
+            text => text.to_owned(),
+        })
+    }
+
+    pub fn encode(string: &str) -> Option<String> {
+        Some(string.to_owned())
+    }
+}
+
+/// Codec wrapping base64 encode/decode.
+pub struct Base64;
+
+impl Base64 {
+    pub fn decode(s: &str) -> Result<Vec<u8>, Error> {
+        Ok(base64::decode(s)?)
+    }
+
+    pub fn encode(b: &[u8]) -> Option<String> {
+        Some(base64::encode(b))
+    }
+}
+
+/// Codec wrapping base64 encode/decode, while ignoring whitespace characters.
+pub struct WhitespaceAwareBase64;
+
+impl WhitespaceAwareBase64 {
+    pub fn decode(s: &str) -> Result<Vec<u8>, Error> {
+        let s: String = s
+            .chars()
+            .filter(|ch| *ch != ' ' && *ch != '\n' && *ch != '\t')
+            .collect();
+        Ok(base64::decode(&s)?)
+    }
+
+    pub fn encode(b: &[u8]) -> Option<String> {
+        Some(base64::encode(b))
+    }
+}
+
+/// Codec for colon-separated bytes of uppercase hexadecimal.
+pub struct ColonSeparatedHex;
+
+impl ColonSeparatedHex {
+    pub fn decode(s: &str) -> Result<Vec<u8>, Error> {
+        let mut bytes = vec![];
+        for i in 0..(1 + s.len()) / 3 {
+            let byte = u8::from_str_radix(&s[3 * i..3 * i + 2], 16)?;
+            if 3 * i + 2 < s.len() {
+                assert_eq!(&s[3 * i + 2..3 * i + 3], ":");
+            }
+            bytes.push(byte);
+        }
+        Ok(bytes)
+    }
+
+    pub fn encode(b: &[u8]) -> Option<String> {
+        let mut bytes = vec![];
+        for byte in b {
+            bytes.push(format!("{:02X}", byte));
+        }
+        Some(bytes.join(":"))
+    }
+}
+
+/// Codec for a JID.
+pub struct JidCodec;
+
+impl JidCodec {
+    pub fn decode(s: &str) -> Result<Jid, Error> {
+        Ok(Jid::from_str(s)?)
+    }
+
+    pub fn encode(jid: &Jid) -> Option<String> {
+        Some(jid.to_string())
+    }
+}

parsers/src/util/macros.rs

@@ -0,0 +1,767 @@
+// Copyright (c) 2017-2018 Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+macro_rules! get_attr {
+    ($elem:ident, $attr:tt, $type:tt) => {
+        get_attr!($elem, $attr, $type, value, value.parse()?)
+    };
+    ($elem:ident, $attr:tt, OptionEmpty, $value:ident, $func:expr) => {
+        match $elem.attr($attr) {
+            Some("") => None,
+            Some($value) => Some($func),
+            None => None,
+        }
+    };
+    ($elem:ident, $attr:tt, Option, $value:ident, $func:expr) => {
+        match $elem.attr($attr) {
+            Some($value) => Some($func),
+            None => None,
+        }
+    };
+    ($elem:ident, $attr:tt, Required, $value:ident, $func:expr) => {
+        match $elem.attr($attr) {
+            Some($value) => $func,
+            None => {
+                return Err(crate::util::error::Error::ParseError(concat!(
+                    "Required attribute '",
+                    $attr,
+                    "' missing."
+                )));
+            }
+        }
+    };
+    ($elem:ident, $attr:tt, RequiredNonEmpty, $value:ident, $func:expr) => {
+        match $elem.attr($attr) {
+            Some("") => {
+                return Err(crate::util::error::Error::ParseError(concat!(
+                    "Required attribute '",
+                    $attr,
+                    "' must not be empty."
+                )));
+            }
+            Some($value) => $func,
+            None => {
+                return Err(crate::util::error::Error::ParseError(concat!(
+                    "Required attribute '",
+                    $attr,
+                    "' missing."
+                )));
+            }
+        }
+    };
+    ($elem:ident, $attr:tt, Default, $value:ident, $func:expr) => {
+        match $elem.attr($attr) {
+            Some($value) => $func,
+            None => ::std::default::Default::default(),
+        }
+    };
+}
+
+macro_rules! generate_attribute {
+    ($(#[$meta:meta])* $elem:ident, $name:tt, {$($(#[$a_meta:meta])* $a:ident => $b:tt),+,}) => (
+        generate_attribute!($(#[$meta])* $elem, $name, {$($(#[$a_meta])* $a => $b),+});
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, {$($(#[$a_meta:meta])* $a:ident => $b:tt),+,}, Default = $default:ident) => (
+        generate_attribute!($(#[$meta])* $elem, $name, {$($(#[$a_meta])* $a => $b),+}, Default = $default);
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, {$($(#[$a_meta:meta])* $a:ident => $b:tt),+}) => (
+        $(#[$meta])*
+        #[derive(Debug, Clone, PartialEq)]
+        pub enum $elem {
+            $(
+                $(#[$a_meta])*
+                $a
+            ),+
+        }
+        impl ::std::str::FromStr for $elem {
+            type Err = crate::util::error::Error;
+            fn from_str(s: &str) -> Result<$elem, crate::util::error::Error> {
+                Ok(match s {
+                    $($b => $elem::$a),+,
+                    _ => return Err(crate::util::error::Error::ParseError(concat!("Unknown value for '", $name, "' attribute."))),
+                })
+            }
+        }
+        impl std::fmt::Display for $elem {
+            fn fmt(&self, fmt: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
+                write!(fmt, "{}", match self {
+                    $($elem::$a => $b),+
+                })
+            }
+        }
+        impl ::minidom::IntoAttributeValue for $elem {
+            fn into_attribute_value(self) -> Option<String> {
+                Some(String::from(match self {
+                    $($elem::$a => $b),+
+                }))
+            }
+        }
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, {$($(#[$a_meta:meta])* $a:ident => $b:tt),+}, Default = $default:ident) => (
+        $(#[$meta])*
+        #[derive(Debug, Clone, PartialEq)]
+        pub enum $elem {
+            $(
+                $(#[$a_meta])*
+                $a
+            ),+
+        }
+        impl ::std::str::FromStr for $elem {
+            type Err = crate::util::error::Error;
+            fn from_str(s: &str) -> Result<$elem, crate::util::error::Error> {
+                Ok(match s {
+                    $($b => $elem::$a),+,
+                    _ => return Err(crate::util::error::Error::ParseError(concat!("Unknown value for '", $name, "' attribute."))),
+                })
+            }
+        }
+        impl ::minidom::IntoAttributeValue for $elem {
+            #[allow(unreachable_patterns)]
+            fn into_attribute_value(self) -> Option<String> {
+                Some(String::from(match self {
+                    $elem::$default => return None,
+                    $($elem::$a => $b),+
+                }))
+            }
+        }
+        impl ::std::default::Default for $elem {
+            fn default() -> $elem {
+                $elem::$default
+            }
+        }
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, ($(#[$meta_symbol:meta])* $symbol:ident => $value:tt)) => (
+        $(#[$meta])*
+        #[derive(Debug, Clone, PartialEq)]
+        pub enum $elem {
+            $(#[$meta_symbol])*
+            $symbol,
+            /// Value when absent.
+            None,
+        }
+        impl ::std::str::FromStr for $elem {
+            type Err = crate::util::error::Error;
+            fn from_str(s: &str) -> Result<Self, crate::util::error::Error> {
+                Ok(match s {
+                    $value => $elem::$symbol,
+                    _ => return Err(crate::util::error::Error::ParseError(concat!("Unknown value for '", $name, "' attribute."))),
+                })
+            }
+        }
+        impl ::minidom::IntoAttributeValue for $elem {
+            fn into_attribute_value(self) -> Option<String> {
+                match self {
+                    $elem::$symbol => Some(String::from($value)),
+                    $elem::None => None
+                }
+            }
+        }
+        impl ::std::default::Default for $elem {
+            fn default() -> $elem {
+                $elem::None
+            }
+        }
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, bool) => (
+        $(#[$meta])*
+        #[derive(Debug, Clone, PartialEq)]
+        pub enum $elem {
+            /// True value, represented by either 'true' or '1'.
+            True,
+            /// False value, represented by either 'false' or '0'.
+            False,
+        }
+        impl ::std::str::FromStr for $elem {
+            type Err = crate::util::error::Error;
+            fn from_str(s: &str) -> Result<Self, crate::util::error::Error> {
+                Ok(match s {
+                    "true" | "1" => $elem::True,
+                    "false" | "0" => $elem::False,
+                    _ => return Err(crate::util::error::Error::ParseError(concat!("Unknown value for '", $name, "' attribute."))),
+                })
+            }
+        }
+        impl ::minidom::IntoAttributeValue for $elem {
+            fn into_attribute_value(self) -> Option<String> {
+                match self {
+                    $elem::True => Some(String::from("true")),
+                    $elem::False => None
+                }
+            }
+        }
+        impl ::std::default::Default for $elem {
+            fn default() -> $elem {
+                $elem::False
+            }
+        }
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $type:tt, Default = $default:expr) => (
+        $(#[$meta])*
+        #[derive(Debug, Clone, PartialEq)]
+        pub struct $elem(pub $type);
+        impl ::std::str::FromStr for $elem {
+            type Err = crate::util::error::Error;
+            fn from_str(s: &str) -> Result<Self, crate::util::error::Error> {
+                Ok($elem($type::from_str(s)?))
+            }
+        }
+        impl ::minidom::IntoAttributeValue for $elem {
+            fn into_attribute_value(self) -> Option<String> {
+                match self {
+                    $elem($default) => None,
+                    $elem(value) => Some(format!("{}", value)),
+                }
+            }
+        }
+        impl ::std::default::Default for $elem {
+            fn default() -> $elem {
+                $elem($default)
+            }
+        }
+    );
+}
+
+macro_rules! generate_element_enum {
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $ns:ident, {$($(#[$enum_meta:meta])* $enum:ident => $enum_name:tt),+,}) => (
+        generate_element_enum!($(#[$meta])* $elem, $name, $ns, {$($(#[$enum_meta])* $enum => $enum_name),+});
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $ns:ident, {$($(#[$enum_meta:meta])* $enum:ident => $enum_name:tt),+}) => (
+        $(#[$meta])*
+        #[derive(Debug, Clone, PartialEq)]
+        pub enum $elem {
+            $(
+                $(#[$enum_meta])*
+                $enum
+            ),+
+        }
+        impl ::std::convert::TryFrom<crate::Element> for $elem {
+            type Error = crate::util::error::Error;
+            fn try_from(elem: crate::Element) -> Result<$elem, crate::util::error::Error> {
+                check_ns_only!(elem, $name, $ns);
+                check_no_children!(elem, $name);
+                check_no_attributes!(elem, $name);
+                Ok(match elem.name() {
+                    $($enum_name => $elem::$enum,)+
+                    _ => return Err(crate::util::error::Error::ParseError(concat!("This is not a ", $name, " element."))),
+                })
+            }
+        }
+        impl From<$elem> for crate::Element {
+            fn from(elem: $elem) -> crate::Element {
+                crate::Element::builder(
+                    match elem {
+                        $($elem::$enum => $enum_name,)+
+                    },
+                    crate::ns::$ns,
+                )
+                    .build()
+            }
+        }
+    );
+}
+
+macro_rules! generate_attribute_enum {
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $ns:ident, $attr:tt, {$($(#[$enum_meta:meta])* $enum:ident => $enum_name:tt),+,}) => (
+        generate_attribute_enum!($(#[$meta])* $elem, $name, $ns, $attr, {$($(#[$enum_meta])* $enum => $enum_name),+});
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $ns:ident, $attr:tt, {$($(#[$enum_meta:meta])* $enum:ident => $enum_name:tt),+}) => (
+        $(#[$meta])*
+        #[derive(Debug, Clone, PartialEq)]
+        pub enum $elem {
+            $(
+                $(#[$enum_meta])*
+                $enum
+            ),+
+        }
+        impl ::std::convert::TryFrom<crate::Element> for $elem {
+            type Error = crate::util::error::Error;
+            fn try_from(elem: crate::Element) -> Result<$elem, crate::util::error::Error> {
+                check_ns_only!(elem, $name, $ns);
+                check_no_children!(elem, $name);
+                check_no_unknown_attributes!(elem, $name, [$attr]);
+                Ok(match get_attr!(elem, $attr, Required) {
+                    $($enum_name => $elem::$enum,)+
+                    _ => return Err(crate::util::error::Error::ParseError(concat!("Invalid ", $name, " ", $attr, " value."))),
+                })
+            }
+        }
+        impl From<$elem> for crate::Element {
+            fn from(elem: $elem) -> crate::Element {
+                crate::Element::builder($name, crate::ns::$ns)
+                    .attr($attr, match elem {
+                         $($elem::$enum => $enum_name,)+
+                     })
+                     .build()
+            }
+        }
+    );
+}
+
+macro_rules! check_self {
+    ($elem:ident, $name:tt, $ns:ident) => {
+        check_self!($elem, $name, $ns, $name);
+    };
+    ($elem:ident, $name:tt, $ns:ident, $pretty_name:tt) => {
+        if !$elem.is($name, crate::ns::$ns) {
+            return Err(crate::util::error::Error::ParseError(concat!(
+                "This is not a ",
+                $pretty_name,
+                " element."
+            )));
+        }
+    };
+}
+
+macro_rules! check_ns_only {
+    ($elem:ident, $name:tt, $ns:ident) => {
+        if !$elem.has_ns(crate::ns::$ns) {
+            return Err(crate::util::error::Error::ParseError(concat!(
+                "This is not a ",
+                $name,
+                " element."
+            )));
+        }
+    };
+}
+
+macro_rules! check_no_children {
+    ($elem:ident, $name:tt) => {
+        #[cfg(not(feature = "disable-validation"))]
+        for _ in $elem.children() {
+            return Err(crate::util::error::Error::ParseError(concat!(
+                "Unknown child in ",
+                $name,
+                " element."
+            )));
+        }
+    };
+}
+
+macro_rules! check_no_attributes {
+    ($elem:ident, $name:tt) => {
+        #[cfg(not(feature = "disable-validation"))]
+        for _ in $elem.attrs() {
+            return Err(crate::util::error::Error::ParseError(concat!(
+                "Unknown attribute in ",
+                $name,
+                " element."
+            )));
+        }
+    };
+}
+
+macro_rules! check_no_unknown_attributes {
+    ($elem:ident, $name:tt, [$($attr:tt),*]) => (
+        #[cfg(not(feature = "disable-validation"))]
+        for (_attr, _) in $elem.attrs() {
+            $(
+                if _attr == $attr {
+                    continue;
+                }
+            )*
+            return Err(crate::util::error::Error::ParseError(concat!("Unknown attribute in ", $name, " element.")));
+        }
+    );
+}
+
+macro_rules! generate_empty_element {
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $ns:ident) => (
+        $(#[$meta])*
+        #[derive(Debug, Clone, PartialEq)]
+        pub struct $elem;
+
+        impl ::std::convert::TryFrom<crate::Element> for $elem {
+            type Error = crate::util::error::Error;
+
+            fn try_from(elem: crate::Element) -> Result<$elem, crate::util::error::Error> {
+                check_self!(elem, $name, $ns);
+                check_no_children!(elem, $name);
+                check_no_attributes!(elem, $name);
+                Ok($elem)
+            }
+        }
+
+        impl From<$elem> for crate::Element {
+            fn from(_: $elem) -> crate::Element {
+                crate::Element::builder($name, crate::ns::$ns)
+                    .build()
+            }
+        }
+    );
+}
+
+macro_rules! generate_id {
+    ($(#[$meta:meta])* $elem:ident) => (
+        $(#[$meta])*
+        #[derive(Debug, Clone, PartialEq, Eq, Hash)]
+        pub struct $elem(pub String);
+        impl ::std::str::FromStr for $elem {
+            type Err = crate::util::error::Error;
+            fn from_str(s: &str) -> Result<$elem, crate::util::error::Error> {
+                // TODO: add a way to parse that differently when needed.
+                Ok($elem(String::from(s)))
+            }
+        }
+        impl ::minidom::IntoAttributeValue for $elem {
+            fn into_attribute_value(self) -> Option<String> {
+                Some(self.0)
+            }
+        }
+    );
+}
+
+macro_rules! generate_elem_id {
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $ns:ident) => (
+        generate_elem_id!($(#[$meta])* $elem, $name, $ns, String);
+        impl ::std::str::FromStr for $elem {
+            type Err = crate::util::error::Error;
+            fn from_str(s: &str) -> Result<$elem, crate::util::error::Error> {
+                // TODO: add a way to parse that differently when needed.
+                Ok($elem(String::from(s)))
+            }
+        }
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $ns:ident, $type:ty) => (
+        $(#[$meta])*
+        #[derive(Debug, Clone, PartialEq, Eq, Hash)]
+        pub struct $elem(pub $type);
+        impl ::std::convert::TryFrom<crate::Element> for $elem {
+            type Error = crate::util::error::Error;
+            fn try_from(elem: crate::Element) -> Result<$elem, crate::util::error::Error> {
+                check_self!(elem, $name, $ns);
+                check_no_children!(elem, $name);
+                check_no_attributes!(elem, $name);
+                // TODO: add a way to parse that differently when needed.
+                Ok($elem(elem.text().parse()?))
+            }
+        }
+        impl From<$elem> for crate::Element {
+            fn from(elem: $elem) -> crate::Element {
+                crate::Element::builder($name, crate::ns::$ns)
+                    .append(elem.0.to_string())
+                    .build()
+            }
+        }
+    );
+}
+
+macro_rules! decl_attr {
+    (OptionEmpty, $type:ty) => (
+        Option<$type>
+    );
+    (Option, $type:ty) => (
+        Option<$type>
+    );
+    (Required, $type:ty) => (
+        $type
+    );
+    (RequiredNonEmpty, $type:ty) => (
+        $type
+    );
+    (Default, $type:ty) => (
+        $type
+    );
+}
+
+macro_rules! start_decl {
+    (Vec, $type:ty) => (
+        Vec<$type>
+    );
+    (Option, $type:ty) => (
+        Option<$type>
+    );
+    (Required, $type:ty) => (
+        $type
+    );
+    (Present, $type:ty) => (
+        bool
+    );
+}
+
+macro_rules! start_parse_elem {
+    ($temp:ident: Vec) => {
+        let mut $temp = Vec::new();
+    };
+    ($temp:ident: Option) => {
+        let mut $temp = None;
+    };
+    ($temp:ident: Required) => {
+        let mut $temp = None;
+    };
+    ($temp:ident: Present) => {
+        let mut $temp = false;
+    };
+}
+
+macro_rules! do_parse {
+    ($elem:ident, Element) => {
+        $elem.clone()
+    };
+    ($elem:ident, String) => {
+        $elem.text()
+    };
+    ($elem:ident, $constructor:ident) => {
+        $constructor::try_from($elem.clone())?
+    };
+}
+
+macro_rules! do_parse_elem {
+    ($temp:ident: Vec = $constructor:ident => $elem:ident, $name:tt, $parent_name:tt) => {
+        $temp.push(do_parse!($elem, $constructor));
+    };
+    ($temp:ident: Option = $constructor:ident => $elem:ident, $name:tt, $parent_name:tt) => {
+        if $temp.is_some() {
+            return Err(crate::util::error::Error::ParseError(concat!(
+                "Element ",
+                $parent_name,
+                " must not have more than one ",
+                $name,
+                " child."
+            )));
+        }
+        $temp = Some(do_parse!($elem, $constructor));
+    };
+    ($temp:ident: Required = $constructor:ident => $elem:ident, $name:tt, $parent_name:tt) => {
+        if $temp.is_some() {
+            return Err(crate::util::error::Error::ParseError(concat!(
+                "Element ",
+                $parent_name,
+                " must not have more than one ",
+                $name,
+                " child."
+            )));
+        }
+        $temp = Some(do_parse!($elem, $constructor));
+    };
+    ($temp:ident: Present = $constructor:ident => $elem:ident, $name:tt, $parent_name:tt) => {
+        if $temp {
+            return Err(crate::util::error::Error::ParseError(concat!(
+                "Element ",
+                $parent_name,
+                " must not have more than one ",
+                $name,
+                " child."
+            )));
+        }
+        $temp = true;
+    };
+}
+
+macro_rules! finish_parse_elem {
+    ($temp:ident: Vec = $name:tt, $parent_name:tt) => {
+        $temp
+    };
+    ($temp:ident: Option = $name:tt, $parent_name:tt) => {
+        $temp
+    };
+    ($temp:ident: Required = $name:tt, $parent_name:tt) => {
+        $temp.ok_or(crate::util::error::Error::ParseError(concat!(
+            "Missing child ",
+            $name,
+            " in ",
+            $parent_name,
+            " element."
+        )))?
+    };
+    ($temp:ident: Present = $name:tt, $parent_name:tt) => {
+        $temp
+    };
+}
+
+macro_rules! generate_serialiser {
+    ($builder:ident, $parent:ident, $elem:ident, Required, String, ($name:tt, $ns:ident)) => {
+        $builder.append(
+            crate::Element::builder($name, crate::ns::$ns)
+                .append(::minidom::Node::Text($parent.$elem)),
+        )
+    };
+    ($builder:ident, $parent:ident, $elem:ident, Option, String, ($name:tt, $ns:ident)) => {
+        $builder.append_all($parent.$elem.map(|elem| {
+            crate::Element::builder($name, crate::ns::$ns).append(::minidom::Node::Text(elem))
+        }))
+    };
+    ($builder:ident, $parent:ident, $elem:ident, Option, $constructor:ident, ($name:tt, *)) => {
+        $builder.append_all(
+            $parent
+                .$elem
+                .map(|elem| ::minidom::Node::Element(crate::Element::from(elem))),
+        )
+    };
+    ($builder:ident, $parent:ident, $elem:ident, Option, $constructor:ident, ($name:tt, $ns:ident)) => {
+        $builder.append_all(
+            $parent
+                .$elem
+                .map(|elem| ::minidom::Node::Element(crate::Element::from(elem))),
+        )
+    };
+    ($builder:ident, $parent:ident, $elem:ident, Vec, $constructor:ident, ($name:tt, $ns:ident)) => {
+        $builder.append_all($parent.$elem.into_iter())
+    };
+    ($builder:ident, $parent:ident, $elem:ident, Present, $constructor:ident, ($name:tt, $ns:ident)) => {
+        $builder.append(::minidom::Node::Element(
+            crate::Element::builder($name, crate::ns::$ns).build(),
+        ))
+    };
+    ($builder:ident, $parent:ident, $elem:ident, $_:ident, $constructor:ident, ($name:tt, $ns:ident)) => {
+        $builder.append(::minidom::Node::Element(crate::Element::from(
+            $parent.$elem,
+        )))
+    };
+}
+
+macro_rules! generate_child_test {
+    ($child:ident, $name:tt, *) => {
+        $child.is($name, ::minidom::NSChoice::Any)
+    };
+    ($child:ident, $name:tt, $ns:tt) => {
+        $child.is($name, crate::ns::$ns)
+    };
+}
+
+macro_rules! generate_element {
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $ns:ident, attributes: [$($(#[$attr_meta:meta])* $attr:ident: $attr_action:tt<$attr_type:ty> = $attr_name:tt),+,]) => (
+        generate_element!($(#[$meta])* $elem, $name, $ns, attributes: [$($(#[$attr_meta])* $attr: $attr_action<$attr_type> = $attr_name),*], children: []);
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $ns:ident, attributes: [$($(#[$attr_meta:meta])* $attr:ident: $attr_action:tt<$attr_type:ty> = $attr_name:tt),+]) => (
+        generate_element!($(#[$meta])* $elem, $name, $ns, attributes: [$($(#[$attr_meta])* $attr: $attr_action<$attr_type> = $attr_name),*], children: []);
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $ns:ident, children: [$($(#[$child_meta:meta])* $child_ident:ident: $coucou:tt<$child_type:ty> = ($child_name:tt, $child_ns:tt) => $child_constructor:ident),*]) => (
+        generate_element!($(#[$meta])* $elem, $name, $ns, attributes: [], children: [$($(#[$child_meta])* $child_ident: $coucou<$child_type> = ($child_name, $child_ns) => $child_constructor),*]);
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $ns:ident, attributes: [$($(#[$attr_meta:meta])* $attr:ident: $attr_action:tt<$attr_type:ty> = $attr_name:tt),*,], children: [$($(#[$child_meta:meta])* $child_ident:ident: $coucou:tt<$child_type:ty> = ($child_name:tt, $child_ns:tt) => $child_constructor:ident),*]) => (
+        generate_element!($(#[$meta])* $elem, $name, $ns, attributes: [$($(#[$attr_meta])* $attr: $attr_action<$attr_type> = $attr_name),*], children: [$($(#[$child_meta])* $child_ident: $coucou<$child_type> = ($child_name, $child_ns) => $child_constructor),*]);
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $ns:ident, text: ($(#[$text_meta:meta])* $text_ident:ident: $codec:ident < $text_type:ty >)) => (
+        generate_element!($(#[$meta])* $elem, $name, $ns, attributes: [], children: [], text: ($(#[$text_meta])* $text_ident: $codec<$text_type>));
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $ns:ident, attributes: [$($(#[$attr_meta:meta])* $attr:ident: $attr_action:tt<$attr_type:ty> = $attr_name:tt),+], text: ($(#[$text_meta:meta])* $text_ident:ident: $codec:ident < $text_type:ty >)) => (
+        generate_element!($(#[$meta])* $elem, $name, $ns, attributes: [$($(#[$attr_meta])* $attr: $attr_action<$attr_type> = $attr_name),*], children: [], text: ($(#[$text_meta])* $text_ident: $codec<$text_type>));
+    );
+    ($(#[$meta:meta])* $elem:ident, $name:tt, $ns:ident, attributes: [$($(#[$attr_meta:meta])* $attr:ident: $attr_action:tt<$attr_type:ty> = $attr_name:tt),*], children: [$($(#[$child_meta:meta])* $child_ident:ident: $coucou:tt<$child_type:ty> = ($child_name:tt, $child_ns:tt) => $child_constructor:ident),*] $(, text: ($(#[$text_meta:meta])* $text_ident:ident: $codec:ident < $text_type:ty >))*) => (
+        $(#[$meta])*
+        #[derive(Debug, Clone, PartialEq)]
+        pub struct $elem {
+            $(
+                $(#[$attr_meta])*
+                pub $attr: decl_attr!($attr_action, $attr_type),
+            )*
+            $(
+                $(#[$child_meta])*
+                pub $child_ident: start_decl!($coucou, $child_type),
+            )*
+            $(
+                $(#[$text_meta])*
+                pub $text_ident: $text_type,
+            )*
+        }
+
+        impl ::std::convert::TryFrom<crate::Element> for $elem {
+            type Error = crate::util::error::Error;
+
+            fn try_from(elem: crate::Element) -> Result<$elem, crate::util::error::Error> {
+                check_self!(elem, $name, $ns);
+                check_no_unknown_attributes!(elem, $name, [$($attr_name),*]);
+                $(
+                    start_parse_elem!($child_ident: $coucou);
+                )*
+                for _child in elem.children() {
+                    $(
+                    if generate_child_test!(_child, $child_name, $child_ns) {
+                        do_parse_elem!($child_ident: $coucou = $child_constructor => _child, $child_name, $name);
+                        continue;
+                    }
+                    )*
+                    return Err(crate::util::error::Error::ParseError(concat!("Unknown child in ", $name, " element.")));
+                }
+                Ok($elem {
+                    $(
+                        $attr: get_attr!(elem, $attr_name, $attr_action),
+                    )*
+                    $(
+                        $child_ident: finish_parse_elem!($child_ident: $coucou = $child_name, $name),
+                    )*
+                    $(
+                        $text_ident: $codec::decode(&elem.text())?,
+                    )*
+                })
+            }
+        }
+
+        impl From<$elem> for crate::Element {
+            fn from(elem: $elem) -> crate::Element {
+                let mut builder = crate::Element::builder($name, crate::ns::$ns);
+                $(
+                    builder = builder.attr($attr_name, elem.$attr);
+                )*
+                $(
+                    builder = generate_serialiser!(builder, elem, $child_ident, $coucou, $child_constructor, ($child_name, $child_ns));
+                )*
+                $(
+                    builder = builder.append_all($codec::encode(&elem.$text_ident).map(::minidom::Node::Text).into_iter());
+                )*
+
+                builder.build()
+            }
+        }
+    );
+}
+
+#[cfg(test)]
+macro_rules! assert_size (
+    ($t:ty, $sz:expr) => (
+        assert_eq!(::std::mem::size_of::<$t>(), $sz);
+    );
+);
+
+// TODO: move that to src/pubsub/mod.rs, once we figure out how to use macros from there.
+macro_rules! impl_pubsub_item {
+    ($item:ident, $ns:ident) => {
+        impl ::std::convert::TryFrom<crate::Element> for $item {
+            type Error = Error;
+
+            fn try_from(elem: crate::Element) -> Result<$item, Error> {
+                check_self!(elem, "item", $ns);
+                check_no_unknown_attributes!(elem, "item", ["id", "publisher"]);
+                let mut payloads = elem.children().cloned().collect::<Vec<_>>();
+                let payload = payloads.pop();
+                if !payloads.is_empty() {
+                    return Err(Error::ParseError(
+                        "More than a single payload in item element.",
+                    ));
+                }
+                Ok($item(crate::pubsub::Item {
+                    id: get_attr!(elem, "id", Option),
+                    publisher: get_attr!(elem, "publisher", Option),
+                    payload,
+                }))
+            }
+        }
+
+        impl From<$item> for crate::Element {
+            fn from(item: $item) -> crate::Element {
+                crate::Element::builder("item", ns::$ns)
+                    .attr("id", item.0.id)
+                    .attr("publisher", item.0.publisher)
+                    .append_all(item.0.payload)
+                    .build()
+            }
+        }
+
+        impl ::std::ops::Deref for $item {
+            type Target = crate::pubsub::Item;
+
+            fn deref(&self) -> &Self::Target {
+                &self.0
+            }
+        }
+
+        impl ::std::ops::DerefMut for $item {
+            fn deref_mut(&mut self) -> &mut Self::Target {
+                &mut self.0
+            }
+        }
+    };
+}

parsers/src/util/mod.rs

@@ -0,0 +1,15 @@
+// Copyright (c) 2019 Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+/// Error type returned by every parser on failure.
+pub mod error;
+
+/// Various helpers.
+pub(crate) mod helpers;
+
+/// Helper macros to parse and serialise more easily.
+#[macro_use]
+mod macros;