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Max Headroom 2022-08-03 20:18:29 +02:00
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2
doc/manual/src/SUMMARY.md.in
View file

@ -34,7 +34,7 @@
- [Building and Testing](expressions/simple-building-testing.md)
- [Generic Builder Syntax](expressions/generic-builder.md)
- [Nix Expression Language](expressions/expression-language.md)
- [Values](expressions/language-values.md)
- [Data Types](expressions/language-values.md)
- [Language Constructs](expressions/language-constructs.md)
- [Operators](expressions/language-operators.md)
- [Derivations](expressions/derivations.md)

4
doc/manual/src/advanced-topics/distributed-builds.md
View file

@ -12,14 +12,14 @@ machine is accessible via SSH and that it has Nix installed. You can
test whether connecting to the remote Nix instance works, e.g.
```console
$ nix ping-store --store ssh://mac
$ nix store ping --store ssh://mac
```
will try to connect to the machine named `mac`. It is possible to
specify an SSH identity file as part of the remote store URI, e.g.
```console
$ nix ping-store --store ssh://mac?ssh-key=/home/alice/my-key
$ nix store ping --store ssh://mac?ssh-key=/home/alice/my-key
```
Since builds should be non-interactive, the key should not have a

258
doc/manual/src/expressions/language-values.md
View file

@ -1,156 +1,164 @@
# Values
# Data Types
## Simple Values
## Primitives
Nix has the following basic data types:
- <a id="type-string" href="#type-string">String</a>
- *Strings* can be written in three ways.
*Strings* can be written in three ways.
The most common way is to enclose the string between double quotes,
e.g., `"foo bar"`. Strings can span multiple lines. The special
characters `"` and `\` and the character sequence `${` must be
escaped by prefixing them with a backslash (`\`). Newlines, carriage
returns and tabs can be written as `\n`, `\r` and `\t`,
respectively.
The most common way is to enclose the string between double quotes,
e.g., `"foo bar"`. Strings can span multiple lines. The special
characters `"` and `\` and the character sequence `${` must be
escaped by prefixing them with a backslash (`\`). Newlines, carriage
returns and tabs can be written as `\n`, `\r` and `\t`,
respectively.
You can include the result of an expression into a string by
enclosing it in `${...}`, a feature known as *antiquotation*. The
enclosed expression must evaluate to something that can be coerced
into a string (meaning that it must be a string, a path, or a
derivation). For instance, rather than writing
You can include the result of an expression into a string by
enclosing it in `${...}`, a feature known as *antiquotation*. The
enclosed expression must evaluate to something that can be coerced
into a string (meaning that it must be a string, a path, or a
derivation). For instance, rather than writing
```nix
"--with-freetype2-library=" + freetype + "/lib"
```
```nix
"--with-freetype2-library=" + freetype + "/lib"
```
(where `freetype` is a derivation), you can instead write the more
natural
(where `freetype` is a derivation), you can instead write the more
natural
```nix
"--with-freetype2-library=${freetype}/lib"
```
```nix
"--with-freetype2-library=${freetype}/lib"
```
The latter is automatically translated to the former. A more
complicated example (from the Nix expression for
[Qt](http://www.trolltech.com/products/qt)):
The latter is automatically translated to the former. A more
complicated example (from the Nix expression for
[Qt](http://www.trolltech.com/products/qt)):
```nix
configureFlags = "
-system-zlib -system-libpng -system-libjpeg
${if openglSupport then "-dlopen-opengl
-L${mesa}/lib -I${mesa}/include
-L${libXmu}/lib -I${libXmu}/include" else ""}
${if threadSupport then "-thread" else "-no-thread"}
";
```
```nix
configureFlags = "
-system-zlib -system-libpng -system-libjpeg
${if openglSupport then "-dlopen-opengl
-L${mesa}/lib -I${mesa}/include
-L${libXmu}/lib -I${libXmu}/include" else ""}
${if threadSupport then "-thread" else "-no-thread"}
";
```
Note that Nix expressions and strings can be arbitrarily nested; in
this case the outer string contains various antiquotations that
themselves contain strings (e.g., `"-thread"`), some of which in
turn contain expressions (e.g., `${mesa}`).
Note that Nix expressions and strings can be arbitrarily nested; in
this case the outer string contains various antiquotations that
themselves contain strings (e.g., `"-thread"`), some of which in
turn contain expressions (e.g., `${mesa}`).
The second way to write string literals is as an *indented string*,
which is enclosed between pairs of *double single-quotes*, like so:
The second way to write string literals is as an *indented string*,
which is enclosed between pairs of *double single-quotes*, like so:
```nix
''
This is the first line.
This is the second line.
This is the third line.
''
```
```nix
''
This is the first line.
This is the second line.
This is the third line.
''
```
This kind of string literal intelligently strips indentation from
the start of each line. To be precise, it strips from each line a
number of spaces equal to the minimal indentation of the string as a
whole (disregarding the indentation of empty lines). For instance,
the first and second line are indented two spaces, while the third
line is indented four spaces. Thus, two spaces are stripped from
each line, so the resulting string is
This kind of string literal intelligently strips indentation from
the start of each line. To be precise, it strips from each line a
number of spaces equal to the minimal indentation of the string as a
whole (disregarding the indentation of empty lines). For instance,
the first and second line are indented two spaces, while the third
line is indented four spaces. Thus, two spaces are stripped from
each line, so the resulting string is
```nix
"This is the first line.\nThis is the second line.\n This is the third line.\n"
```
```nix
"This is the first line.\nThis is the second line.\n This is the third line.\n"
```
Note that the whitespace and newline following the opening `''` is
ignored if there is no non-whitespace text on the initial line.
Note that the whitespace and newline following the opening `''` is
ignored if there is no non-whitespace text on the initial line.
Antiquotation (`${expr}`) is supported in indented strings.
Antiquotation (`${expr}`) is supported in indented strings.
Since `${` and `''` have special meaning in indented strings, you
need a way to quote them. `$` can be escaped by prefixing it with
`''` (that is, two single quotes), i.e., `''$`. `''` can be escaped
by prefixing it with `'`, i.e., `'''`. `$` removes any special
meaning from the following `$`. Linefeed, carriage-return and tab
characters can be written as `''\n`, `''\r`, `''\t`, and `''\`
escapes any other character.
Since `${` and `''` have special meaning in indented strings, you
need a way to quote them. `$` can be escaped by prefixing it with
`''` (that is, two single quotes), i.e., `''$`. `''` can be escaped
by prefixing it with `'`, i.e., `'''`. `$` removes any special
meaning from the following `$`. Linefeed, carriage-return and tab
characters can be written as `''\n`, `''\r`, `''\t`, and `''\`
escapes any other character.
Indented strings are primarily useful in that they allow multi-line
string literals to follow the indentation of the enclosing Nix
expression, and that less escaping is typically necessary for
strings representing languages such as shell scripts and
configuration files because `''` is much less common than `"`.
Example:
Indented strings are primarily useful in that they allow multi-line
string literals to follow the indentation of the enclosing Nix
expression, and that less escaping is typically necessary for
strings representing languages such as shell scripts and
configuration files because `''` is much less common than `"`.
Example:
```nix
stdenv.mkDerivation {
...
postInstall =
''
mkdir $out/bin $out/etc
cp foo $out/bin
echo "Hello World" > $out/etc/foo.conf
${if enableBar then "cp bar $out/bin" else ""}
'';
...
}
```
```nix
stdenv.mkDerivation {
...
postInstall =
''
mkdir $out/bin $out/etc
cp foo $out/bin
echo "Hello World" > $out/etc/foo.conf
${if enableBar then "cp bar $out/bin" else ""}
'';
...
}
```
Finally, as a convenience, *URIs* as defined in appendix B of
[RFC 2396](http://www.ietf.org/rfc/rfc2396.txt) can be written *as
is*, without quotes. For instance, the string
`"http://example.org/foo.tar.bz2"` can also be written as
`http://example.org/foo.tar.bz2`.
Finally, as a convenience, *URIs* as defined in appendix B of
[RFC 2396](http://www.ietf.org/rfc/rfc2396.txt) can be written *as
is*, without quotes. For instance, the string
`"http://example.org/foo.tar.bz2"` can also be written as
`http://example.org/foo.tar.bz2`.
- Numbers, which can be *integers* (like `123`) or *floating point*
(like `123.43` or `.27e13`).
- <a id="type-number" href="#type-number">Number</a>
Numbers are type-compatible: pure integer operations will always
return integers, whereas any operation involving at least one
floating point number will have a floating point number as a result.
Numbers, which can be *integers* (like `123`) or *floating point*
(like `123.43` or `.27e13`).
- *Paths*, e.g., `/bin/sh` or `./builder.sh`. A path must contain at
least one slash to be recognised as such. For instance, `builder.sh`
is not a path: it's parsed as an expression that selects the
attribute `sh` from the variable `builder`. If the file name is
relative, i.e., if it does not begin with a slash, it is made
absolute at parse time relative to the directory of the Nix
expression that contained it. For instance, if a Nix expression in
`/foo/bar/bla.nix` refers to `../xyzzy/fnord.nix`, the absolute path
is `/foo/xyzzy/fnord.nix`.
Numbers are type-compatible: pure integer operations will always
return integers, whereas any operation involving at least one
floating point number will have a floating point number as a result.
If the first component of a path is a `~`, it is interpreted as if
the rest of the path were relative to the user's home directory.
e.g. `~/foo` would be equivalent to `/home/edolstra/foo` for a user
whose home directory is `/home/edolstra`.
- <a id="type-path" href="#type-path">Path</a>
Paths can also be specified between angle brackets, e.g.
`<nixpkgs>`. This means that the directories listed in the
environment variable `NIX_PATH` will be searched for the given file
or directory name.
*Paths*, e.g., `/bin/sh` or `./builder.sh`. A path must contain at
least one slash to be recognised as such. For instance, `builder.sh`
is not a path: it's parsed as an expression that selects the
attribute `sh` from the variable `builder`. If the file name is
relative, i.e., if it does not begin with a slash, it is made
absolute at parse time relative to the directory of the Nix
expression that contained it. For instance, if a Nix expression in
`/foo/bar/bla.nix` refers to `../xyzzy/fnord.nix`, the absolute path
is `/foo/xyzzy/fnord.nix`.
Antiquotation is supported in any paths except those in angle brackets.
`./${foo}-${bar}.nix` is a more convenient way of writing
`./. + "/" + foo + "-" + bar + ".nix"` or `./. + "/${foo}-${bar}.nix"`. At
least one slash must appear *before* any antiquotations for this to be
recognized as a path. `a.${foo}/b.${bar}` is a syntactically valid division
operation. `./a.${foo}/b.${bar}` is a path.
If the first component of a path is a `~`, it is interpreted as if
the rest of the path were relative to the user's home directory.
e.g. `~/foo` would be equivalent to `/home/edolstra/foo` for a user
whose home directory is `/home/edolstra`.
- *Booleans* with values `true` and `false`.
Paths can also be specified between angle brackets, e.g.
`<nixpkgs>`. This means that the directories listed in the
environment variable `NIX_PATH` will be searched for the given file
or directory name.
- The null value, denoted as `null`.
Antiquotation is supported in any paths except those in angle brackets.
`./${foo}-${bar}.nix` is a more convenient way of writing
`./. + "/" + foo + "-" + bar + ".nix"` or `./. + "/${foo}-${bar}.nix"`. At
least one slash must appear *before* any antiquotations for this to be
recognized as a path. `a.${foo}/b.${bar}` is a syntactically valid division
operation. `./a.${foo}/b.${bar}` is a path.
## Lists
- <a id="type-boolean" href="#type-boolean">Boolean</a>
*Booleans* with values `true` and `false`.
- <a id="type-null" href="#type-null">Null</a>
The null value, denoted as `null`.
## List
Lists are formed by enclosing a whitespace-separated list of values
between square brackets. For example,
@ -172,9 +180,9 @@ function and the fifth being a set.
Note that lists are only lazy in values, and they are strict in length.
## Attribute Sets
## Attribute Set
Attribute sets are collections of name-value-pairs (called *attributes*) enclosed in curly brackets (`{ }`).
An attribute set is a collection of name-value-pairs (called *attributes*) enclosed in curly brackets (`{ }`).
Names and values are separated by an equal sign (`=`).
Each value is an arbitrary expression terminated by a semicolon (`;`).

12
src/libexpr/eval.cc
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@ -2501,18 +2501,18 @@ void EvalState::printStats()
}
{
auto list = topObj.list("functions");
for (auto & i : functionCalls) {
for (auto & [fun, count] : functionCalls) {
auto obj = list.object();
if (i.first->name)
obj.attr("name", (const std::string &) i.first->name);
if (fun->name)
obj.attr("name", (std::string_view) symbols[fun->name]);
else
obj.attr("name", nullptr);
if (auto pos = positions[i.first->pos]) {
obj.attr("file", (const std::string &) pos.file);
if (auto pos = positions[fun->pos]) {
obj.attr("file", (std::string_view) pos.file);
obj.attr("line", pos.line);
obj.attr("column", pos.column);
}
obj.attr("count", i.second);
obj.attr("count", count);
}
}
{

21
src/libutil/json.cc
View file

@ -6,7 +6,8 @@
namespace nix {
void toJSON(std::ostream & str, const char * start, const char * end)
template<>
void toJSON<std::string_view>(std::ostream & str, const std::string_view & s)
{
constexpr size_t BUF_SIZE = 4096;
char buf[BUF_SIZE + 7]; // BUF_SIZE + largest single sequence of puts
@ -21,7 +22,7 @@ void toJSON(std::ostream & str, const char * start, const char * end)
};
put('"');
for (auto i = start; i != end; i++) {
for (auto i = s.begin(); i != s.end(); i++) {
if (bufPos >= BUF_SIZE) flush();
if (*i == '\"' || *i == '\\') { put('\\'); put(*i); }
else if (*i == '\n') { put('\\'); put('n'); }
@ -44,7 +45,7 @@ void toJSON(std::ostream & str, const char * start, const char * end)
void toJSON(std::ostream & str, const char * s)
{
if (!s) str << "null"; else toJSON(str, s, s + strlen(s));
if (!s) str << "null"; else toJSON(str, std::string_view(s));
}
template<> void toJSON<int>(std::ostream & str, const int & n) { str << n; }
@ -55,11 +56,7 @@ template<> void toJSON<long long>(std::ostream & str, const long long & n) { str
template<> void toJSON<unsigned long long>(std::ostream & str, const unsigned long long & n) { str << n; }
template<> void toJSON<float>(std::ostream & str, const float & n) { str << n; }
template<> void toJSON<double>(std::ostream & str, const double & n) { str << n; }
template<> void toJSON<std::string>(std::ostream & str, const std::string & s)
{
toJSON(str, s.c_str(), s.c_str() + s.size());
}
template<> void toJSON<std::string>(std::ostream & str, const std::string & s) { toJSON(str, (std::string_view) s); }
template<> void toJSON<bool>(std::ostream & str, const bool & b)
{
@ -154,7 +151,7 @@ JSONObject::~JSONObject()
}
}
void JSONObject::attr(const std::string & s)
void JSONObject::attr(std::string_view s)
{
comma();
toJSON(state->str, s);
@ -162,19 +159,19 @@ void JSONObject::attr(const std::string & s)
if (state->indent) state->str << ' ';
}
JSONList JSONObject::list(const std::string & name)
JSONList JSONObject::list(std::string_view name)
{
attr(name);
return JSONList(state);
}
JSONObject JSONObject::object(const std::string & name)
JSONObject JSONObject::object(std::string_view name)
{
attr(name);
return JSONObject(state);
}
JSONPlaceholder JSONObject::placeholder(const std::string & name)
JSONPlaceholder JSONObject::placeholder(std::string_view name)
{
attr(name);
return JSONPlaceholder(state);

11
src/libutil/json.hh
View file

@ -6,7 +6,6 @@
namespace nix {
void toJSON(std::ostream & str, const char * start, const char * end);
void toJSON(std::ostream & str, const char * s);
template<typename T>
@ -107,7 +106,7 @@ private:
open();
}
void attr(const std::string & s);
void attr(std::string_view s);
public:
@ -128,18 +127,18 @@ public:
~JSONObject();
template<typename T>
JSONObject & attr(const std::string & name, const T & v)
JSONObject & attr(std::string_view name, const T & v)
{
attr(name);
toJSON(state->str, v);
return *this;
}
JSONList list(const std::string & name);
JSONList list(std::string_view name);
JSONObject object(const std::string & name);
JSONObject object(std::string_view name);
JSONPlaceholder placeholder(const std::string & name);
JSONPlaceholder placeholder(std::string_view name);
};
class JSONPlaceholder : JSONWriter

4
src/libutil/tests/json.cc
View file

@ -102,8 +102,8 @@ namespace nix {
TEST(toJSON, substringEscape) {
std::stringstream out;
const char *s = "foo\t";
toJSON(out, s+3, s + strlen(s));
std::string_view s = "foo\t";
toJSON(out, s.substr(3));
ASSERT_EQ(out.str(), "\"\\t\"");
}