Allow dynamic derivation deps in `inputDrvs`

We use the same nested map representation we used for goals, again in
order to save space. We might someday want to combine with `inputDrvs`,
by doing `V = bool` instead of `V = std::set<OutputName>`, but we are
not doing that yet for sake of a smaller diff.

The ATerm format for Derivations also needs to be extended, in addition
to the in-memory format. To accomodate this, we added a new basic
versioning scheme, so old versions of Nix will get nice errors. (And
going forward, if the ATerm format changes again the errors will be even
better.)

`parsedStrings`, an internal function used as part of parsing
derivations in A-Term format, used to consume the final `]` but expect
the initial `[` to already be consumed. This made for what looked like
unbalanced brackets at callsites, which was confusing. Now it consumes
both which is hopefully less confusing.

As part of testing, we also created a unit test for the A-Term format for
regular non-experimental derivations too.

Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>

Apply suggestions from code review

Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>

1 files changed, 52 insertions, 25 deletions

diff --git a/src/libutil/comparator.hh b/src/libutil/comparator.hh
index 7982fdc5e..a4d20a675 100644
--- a/src/libutil/comparator.hh
+++ b/src/libutil/comparator.hh
@@ -1,21 +1,48 @@
 #pragma once
 ///@file
 
+#define DECLARE_ONE_CMP(PRE, QUAL, COMPARATOR, MY_TYPE) \
+    PRE bool QUAL operator COMPARATOR(const MY_TYPE & other) const;
+#define DECLARE_EQUAL(prefix, qualification, my_type) \
+    DECLARE_ONE_CMP(prefix, qualification, ==, my_type)
+#define DECLARE_LEQ(prefix, qualification, my_type) \
+    DECLARE_ONE_CMP(prefix, qualification, <, my_type)
+#define DECLARE_NEQ(prefix, qualification, my_type) \
+    DECLARE_ONE_CMP(prefix, qualification, !=, my_type)
+
+#define GENERATE_ONE_CMP(PRE, QUAL, COMPARATOR, MY_TYPE, ...) \
+    PRE bool QUAL operator COMPARATOR(const MY_TYPE & other) const { \
+      __VA_OPT__(const MY_TYPE * me = this;) \
+      auto fields1 = std::make_tuple( __VA_ARGS__ ); \
+      __VA_OPT__(me = &other;) \
+      auto fields2 = std::make_tuple( __VA_ARGS__ ); \
+      return fields1 COMPARATOR fields2; \
+    }
+#define GENERATE_EQUAL(prefix, qualification, my_type, args...) \
+    GENERATE_ONE_CMP(prefix, qualification, ==, my_type, args)
+#define GENERATE_LEQ(prefix, qualification, my_type, args...) \
+    GENERATE_ONE_CMP(prefix, qualification, <, my_type, args)
+#define GENERATE_NEQ(prefix, qualification, my_type, args...) \
+    GENERATE_ONE_CMP(prefix, qualification, !=, my_type, args)
+
 /**
  * Declare comparison methods without defining them.
  */
-#define DECLARE_ONE_CMP(COMPARATOR, MY_TYPE) \
-    bool operator COMPARATOR(const MY_TYPE & other) const;
-#define DECLARE_EQUAL(my_type) \
-    DECLARE_ONE_CMP(==, my_type)
-#define DECLARE_LEQ(my_type) \
-    DECLARE_ONE_CMP(<, my_type)
-#define DECLARE_NEQ(my_type) \
-    DECLARE_ONE_CMP(!=, my_type)
 #define DECLARE_CMP(my_type) \
-    DECLARE_EQUAL(my_type) \
-    DECLARE_LEQ(my_type) \
-    DECLARE_NEQ(my_type)
+    DECLARE_EQUAL(,,my_type) \
+    DECLARE_LEQ(,,my_type) \
+    DECLARE_NEQ(,,my_type)
+
+/**
+ * @param prefix This is for something before each declaration like
+ * `template<classname Foo>`.
+ *
+ * @param my_type the type are defining operators for.
+ */
+#define DECLARE_CMP_EXT(prefix, qualification, my_type) \
+    DECLARE_EQUAL(prefix, qualification, my_type) \
+    DECLARE_LEQ(prefix, qualification, my_type) \
+    DECLARE_NEQ(prefix, qualification, my_type)
 
 /**
  * Awful hacky generation of the comparison operators by doing a lexicographic
@@ -33,18 +60,18 @@
  * }
  * ```
  */
-#define GENERATE_ONE_CMP(COMPARATOR, MY_TYPE, ...) \
-    bool operator COMPARATOR(const MY_TYPE& other) const { \
-      __VA_OPT__(const MY_TYPE* me = this;) \
-      auto fields1 = std::make_tuple( __VA_ARGS__ ); \
-      __VA_OPT__(me = &other;) \
-      auto fields2 = std::make_tuple( __VA_ARGS__ ); \
-      return fields1 COMPARATOR fields2; \
-    }
-#define GENERATE_EQUAL(args...) GENERATE_ONE_CMP(==, args)
-#define GENERATE_LEQ(args...) GENERATE_ONE_CMP(<, args)
-#define GENERATE_NEQ(args...) GENERATE_ONE_CMP(!=, args)
 #define GENERATE_CMP(args...) \
-    GENERATE_EQUAL(args) \
-    GENERATE_LEQ(args) \
-    GENERATE_NEQ(args)
+    GENERATE_EQUAL(,,args) \
+    GENERATE_LEQ(,,args) \
+    GENERATE_NEQ(,,args)
+
+/**
+ * @param prefix This is for something before each declaration like
+ * `template<classname Foo>`.
+ *
+ * @param my_type the type are defining operators for.
+ */
+#define GENERATE_CMP_EXT(prefix, my_type, args...) \
+    GENERATE_EQUAL(prefix, my_type ::, my_type, args) \
+    GENERATE_LEQ(prefix, my_type ::, my_type, args) \
+    GENERATE_NEQ(prefix, my_type ::, my_type, args)