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better i18n Accept-Language parsing to properly support examples (+ as standalone function) #1850

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merged 3 commits into from
Jul 18, 2017
Merged

better i18n Accept-Language parsing to properly support examples (+ as standalone function) #1850

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2c667b4
More flexible standalone parsing of Accept-Language
WebFreak001 Jul 18, 2017
15b7c65
Adhere to codestyle
WebFreak001 Jul 18, 2017
f3be492
Use std.range.only & more unittests
WebFreak001 Jul 18, 2017
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113 changes: 88 additions & 25 deletions web/vibe/web/i18n.d
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@ module vibe.web.i18n;
import vibe.http.server : HTTPServerRequest;

import std.algorithm : canFind, min, startsWith;

import std.range.primitives : isForwardRange;

/**
Annotates an interface method or class with translation information.
Expand Down Expand Up @@ -62,6 +62,7 @@ unittest {

struct TranslationContext {
import std.typetuple;
// A language can be in the form en_US, en-US or en. Put the languages you want to prioritize first.
alias languages = TypeTuple!("en_US", "de_DE", "fr_FR");
//mixin translationModule!"app";
//mixin translationModule!"somelib";
Expand All @@ -70,7 +71,7 @@ unittest {
// "Accept-Language" header
static string determineLanguage(scope HTTPServerRequest req)
{
if (!req.session) return null; // use default language
if (!req.session) return req.determineLanguageByHeader(languages); // default behaviour using "Accept-Language" header
return req.session.get("language", "");
}
}
Expand Down Expand Up @@ -221,11 +222,93 @@ template tr(CTX, string LANG)
}
}

package string determineLanguage(alias METHOD)(scope HTTPServerRequest req)
/// Determines a language code from the value of a header string.
/// Returns: The best match from the Accept-Language header for a language. `null` if there is no supported language.
public string determineLanguageByHeader(T)(string accept_language, T allowed_languages) @safe pure @nogc
if (isForwardRange!T)
{
import std.algorithm : splitter, countUntil;
import std.string : indexOf;
import std.array;

// TODO: verify that allowed_languages doesn't contain a mix of languages with and without extra specifier for the same lanaguage (but only if one without specifier comes before those with specifier)
// Implementing that feature should try to give a compile time warning and not change the behaviour of this function.

if (!accept_language.length)
return null;

string fallback = null;
foreach (accept; accept_language.splitter(",")) {
auto sidx = accept.indexOf(';');
if (sidx >= 0)
accept = accept[0 .. sidx];

string alang, aextra;
auto asep = accept.countUntil!(a => a == '_' || a == '-');
if (asep < 0)
alang = accept;
else {
alang = accept[0 .. asep];
aextra = accept[asep + 1 .. $];
}

foreach (lang; allowed_languages) {
string lcode, lextra;
sidx = lang.countUntil!(a => a == '_' || a == '-');
if (sidx < 0)
lcode = lang;
else {
lcode = lang[0 .. sidx];
lextra = lang[sidx + 1 .. $];
}
// request en_US == serve en_US
if (lcode == alang && lextra == aextra)
return lang;
// request en_* == serve en
if (lcode == alang && !lextra.length)
return lang;
// request en* == serve en_* && be first occurence
if (lcode == alang && lextra.length && !fallback.length)
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There is one fallback case missing here: determineLanguageByHeader("en_US,enCA", ["en_GB"]) == "en_GB"). This should ideally still apply, though: determineLanguageByHeader("en_US,enCA", ["en_GB", "en"]) == "en").

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those tests already work, assuming the allowed_languages argument is valid (most generic languages should be to the right of the specific ones)

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Nevermind, I misread this as !lextra.length and it's actually fine like it is.

fallback = lang;
}
}

return fallback;
}

/// ditto
public string determineLanguageByHeader(Tuple...)(string accept_language, Tuple allowed_languages) @safe pure
{
return determineLanguageByHeader(accept_language, [allowed_languages]);
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[allowed_languages] -> std.range.only(allowed_languages) to avoid GC allocations.

}

/// ditto
public string determineLanguageByHeader(T)(HTTPServerRequest req, T allowed_languages) @safe pure
if (isForwardRange!T)
{
return determineLanguageByHeader(req.headers.get("Accept-Language", null), allowed_languages);
}

/// ditto
public string determineLanguageByHeader(Tuple...)(HTTPServerRequest req, Tuple allowed_languages) @safe pure
{
return determineLanguageByHeader(req.headers.get("Accept-Language", null), [allowed_languages]);
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also only(...)

}

@safe unittest {
assert(determineLanguageByHeader("de,de-DE;q=0.8,en;q=0.6,en-US;q=0.4", ["en-US", "de_DE", "de_CH"]) == "de_DE");
assert(determineLanguageByHeader("de,de-CH;q=0.8,en;q=0.6,en-US;q=0.4", ["en_US", "de_DE", "de-CH"]) == "de-CH");
assert(determineLanguageByHeader("en_CA,en_US", ["ja_JP", "en"]) == "en");
assert(determineLanguageByHeader("en", ["ja_JP", "en"]) == "en");
assert(determineLanguageByHeader("en", ["ja_JP", "en_US"]) == "en_US");
assert(determineLanguageByHeader("en_US", ["ja-JP", "en"]) == "en");
assert(determineLanguageByHeader("de,de-DE;q=0.8,en;q=0.6,en-US;q=0.4", ["ja_JP"]) is null);
assert(determineLanguageByHeader("de, de-DE ;q=0.8 , en ;q=0.6 , en-US;q=0.4", ["de-DE"]) == "de-DE");
assert(determineLanguageByHeader("en_GB", ["en_US"]) == "en_US");
assert(determineLanguageByHeader("de_DE", ["en_US"]) is null);
}

package string determineLanguage(alias METHOD)(scope HTTPServerRequest req)
{
alias CTX = GetTranslationContext!METHOD;

static if (!is(CTX == void)) {
Expand All @@ -234,27 +317,7 @@ package string determineLanguage(alias METHOD)(scope HTTPServerRequest req)
"determineLanguage in a translation context must return a language string.");
return CTX.determineLanguage(req);
} else {
auto accept_lang = req.headers.get("Accept-Language", null);

size_t csidx = 0;
while (accept_lang.length) {
auto cidx = accept_lang[csidx .. $].indexOf(',');
if (cidx < 0) cidx = accept_lang.length;
auto entry = accept_lang[csidx .. csidx + cidx];
auto sidx = entry.indexOf(';');
if (sidx < 0) sidx = entry.length;
auto entrylang = entry[0 .. sidx];

foreach (lang; CTX.languages) {
if (entrylang == replace(lang, "_", "-")) return lang;
if (entrylang == split(lang, "_")[0]) return lang; // FIXME: ensure that only one single-lang entry exists!
}

if (cidx >= accept_lang.length) break;
accept_lang = accept_lang[cidx+1 .. $];
}

return null;
return determineLanguageByHeader(req, CTX.languages);
}
} else return null;
}
Expand Down