Add configurable imports to the language specification.
Change-Id: I0b36c187a1ec13fe4c65acab762b5f7d46869e39
Reviewed-on: https://dart-review.googlesource.com/46440
Commit-Queue: Lasse R.H. Nielsen <lrn@google.com>
Reviewed-by: Leaf Petersen <leafp@google.com>
Reviewed-by: Erik Ernst <eernst@google.com>
diff --git a/docs/language/dartLangSpec.tex b/docs/language/dartLangSpec.tex
index 17d6731..d48dbdc 100644
--- a/docs/language/dartLangSpec.tex
+++ b/docs/language/dartLangSpec.tex
@@ -47,6 +47,7 @@
% local function evaluates to the closurization of that declaration.
% - Make `mixin` and `interface` built-in identifiers.
% - Make `async` *not* a reserved word inside async functions.
+<<<<<<< HEAD
% - Add 'Class Member Conflicts', simplifying and adjusting rules about
% member declaration conflicts beyond "`n` declared twice in one scope".
% - Specify that integer literals are limited to signed 64-bit values,
@@ -55,6 +56,9 @@
% - Specify variance and super-bounded types.
% - Introduce `subterm` and `immediate subterm`.
% - Introduce `top type`.
+=======
+% - Specify configurable imports.
+>>>>>>> Update changelog.
%
% 1.15
% - Change how language specification describes control flow.
@@ -8829,12 +8833,15 @@
{\bf scriptTag:}`\#!' {\escapegrammar (\~{}NEWLINE)*} NEWLINE
.
-{\bf libraryName:}metadata \LIBRARY{} identifier (`{\escapegrammar .}' identifier)* `{\escapegrammar ;}'
+{\bf libraryName:}metadata \LIBRARY{} dottedIdentifierList `{\escapegrammar ;}'
.
{\bf importOrExport:}libraryImport;
libraryExport
.
+
+{\bf dottedIdentifierList:} identifier (`{\escapegrammar .}' identifier)*
+ .
\end{grammar}
\LMHash{}
@@ -8891,7 +8898,7 @@
{\bf libraryImport:}metadata importSpecification
.
-{\bf importSpecification:}\IMPORT{} uri (\AS{} identifier)? combinator* `{\escapegrammar ;}';
+{\bf importSpecification:}\IMPORT{} configurableUri (\AS{} identifier)? combinator* `{\escapegrammar ;}';
\IMPORT{} uri \DEFERRED{} \AS{} identifier combinator* `{\escapegrammar ;}'
.
@@ -9156,7 +9163,7 @@
The namespace that $L$ exports is known as its {\em exported namespace}.
\begin{grammar}
-{\bf libraryExport:}metadata \EXPORT{} uri combinator* `{\escapegrammar ;}'
+{\bf libraryExport:}metadata \EXPORT{} configurableUri combinator* `{\escapegrammar ;}'
.
\end{grammar}
@@ -9318,12 +9325,50 @@
\begin{grammar}
{\bf uri:}stringLiteral
.
+{\bf configurableUri:} uri configurationUri*
+ .
+{\bf configurationUri:} \IF{} `(' uriTest `)' uri
+ .
+{\bf uriTest:} dottedIdentifierList (`==' stringLiteral)?
+ .
\end{grammar}
\LMHash{}
It is a compile-time error if the string literal $x$ that describes a URI is not a compile-time constant, or if $x$ involves string interpolation.
\LMHash{}
+It is a compile-time error if the string literal $x$ that is used in a {\em uriTest} is not a compile-time constant, or if $x$ involves string interpolation.
+
+\LMHash{} A {\em configurable URI} $c$ of the form \code{\metavar{uri} $\metavar{configurationUri}_1$ \ldots $\metavar{configurationUri}_n$} {\em specifies a URI} as follows:
+\begin{itemize}
+\item{} Let $u$ be \metavar{uri}.
+\item{} For each of the following configuration URIs of the form \code{\IF{} ($\metavar{test}_i$) $\metavar{uri}_i$}, in source order, do the following.
+\begin{itemize}
+ \item{} If $\metavar{test}_i$ is \code{\metavar{ids}} with no \code{==} clause, it is
+ equivalent to \code{\metavar{ids} == "true"}.
+ \item{} If $\metavar{test}_i$ is \code{\metavar{ids} == \metavar{string}},
+ then create a string, \metavar{key}, from \metavar{ids}
+ by concatenating the identfiers and dots,
+ omitting any spaces between them that may occur in the source.
+ \item{} Look up \metavar{key} in the available compilation {\em environment}.
+ \commentary{
+ The compilation environment is provided by the platform.
+ It maps some string keys to string values,
+ and can be accessed programmatically using the
+ \code{const String.fromEnvironment} constructor.
+ Tools may choose to only make some parts of the compilation environment
+ available for choosing configuration URIs.
+ }
+ \item{} If the environment contains an entry for \metavar{key} and the
+ associated value is equal, as a constant string value, to the value of
+ the string literal \metavar{string},
+ then let $u$ be $\metavar{uri}_i$ and stop iterating the configuration URIs.
+ \item{} Otherwise proceed to the next configuration URI.
+\end{itemize}
+\item{} The URI specified by $c$ is $u$.
+\end{itemize}
+
+\LMHash{}
This specification does not discuss the interpretation of URIs, with the following exceptions.
\rationale{
