Generators can have extra target dependencies. Closes #4131.

docs/markdown/Reference-manual.md

@@ -714,6 +714,9 @@ following:
 
 - `arguments` a list of template strings that will be the command line
   arguments passed to the executable
+- `depends` is an array of build targets that must be built before this
+  generator can be run. This is used if you have a generator that calls
+  a second executable that is built in this project. Available since 0.51.0
 - `depfile` is a template string pointing to a dependency file that a
   generator can write listing all the additional files this target
   depends on, for example a C compiler would list all the header files

docs/markdown/snippets/gendeps.md

@@ -0,0 +1,16 @@
+## Generators have a new `depends` keyword argument
+
+Generators can now specify extra dependencies with the `depends`
+keyword argument. It matches the behaviour of the same argument in
+other functions and specifies that the given targets must be built
+before the generator can be run. This is used in cases such as this
+one where you need to tell a generator to indirectly invoke a
+different program.
+
+```meson
+exe = executable(...)
+cg = generator(program_runner,
+    output: ['@BASENAME@.c'],
+    arguments: ['--use-tool=' + exe.full_path(), '@INPUT@', '@OUTPUT@'],
+    depends: exe)
+```

mesonbuild/backend/ninjabackend.py

@@ -1800,6 +1800,7 @@ def generate_genlist_for_target(self, genlist, target):
                 cmd = cmdlist
 
             elem = NinjaBuildElement(self.all_outputs, outfiles, rulename, infilename)
+            elem.add_dep([self.get_target_filename(x) for x in generator.depends])
             if generator.depfile is not None:
                 elem.add_item('DEPFILE', depfile)
             if len(extra_dependencies) > 0:

mesonbuild/build.py

@@ -1273,6 +1273,7 @@ def __init__(self, args, kwargs):
         self.exe = exe
         self.depfile = None
         self.capture = False
+        self.depends = []
         self.process_kwargs(kwargs)
 
     def __repr__(self):
@@ -1321,6 +1322,12 @@ def process_kwargs(self, kwargs):
             if not isinstance(capture, bool):
                 raise InvalidArguments('Capture must be boolean.')
             self.capture = capture
+        if 'depends' in kwargs:
+            depends = listify(kwargs['depends'], unholder=True)
+            for d in depends:
+                if not isinstance(d, BuildTarget):
+                    raise InvalidArguments('Depends entries must be build targets.')
+                self.depends.append(d)
 
     def get_base_outnames(self, inname):
         plainname = os.path.basename(inname)

mesonbuild/interpreter.py

@@ -1983,7 +1983,12 @@ def get_cross_property_method(self, args, kwargs):
                                            },
                     'executable': build.known_exe_kwargs,
                     'find_program': {'required', 'native'},
-                    'generator': {'arguments', 'output', 'depfile', 'capture', 'preserve_path_from'},
+                    'generator': {'arguments',
+                                  'output',
+                                  'depends',
+                                  'depfile',
+                                  'capture',
+                                  'preserve_path_from'},
                     'include_directories': {'is_system'},
                     'install_data': {'install_dir', 'install_mode', 'rename', 'sources'},
                     'install_headers': {'install_dir', 'install_mode', 'subdir'},

test cases/common/27 pipeline/depends/copyrunner.py

@@ -0,0 +1,7 @@
+#!/usr/bin/env python3
+
+import sys, subprocess
+
+prog, infile, outfile = sys.argv[1:]
+
+subprocess.check_call([prog, infile, outfile])

test cases/common/27 pipeline/depends/filecopier.c

@@ -0,0 +1,22 @@
+#include<stdio.h>
+#include<assert.h>
+
+#define BUFSIZE 1024
+
+int main(int argc, char **argv) {
+    char buffer[BUFSIZE];
+    size_t num_read;
+    size_t num_written;
+    FILE *fin = fopen(argv[1], "rb");
+    FILE *fout;
+    assert(fin);
+    num_read = fread(buffer, 1, BUFSIZE, fin);
+    assert(num_read > 0);
+    fclose(fin);
+    fout = fopen(argv[2], "wb");
+    assert(fout);
+    num_written = fwrite(buffer, 1, num_read, fout);
+    assert(num_written == num_read);
+    fclose(fout);
+    return 0;
+}

test cases/common/27 pipeline/depends/libsrc.c.in

@@ -0,0 +1,3 @@
+int func() {
+    return 42;
+}

test cases/common/27 pipeline/depends/meson.build

@@ -0,0 +1,11 @@
+runner = find_program('copyrunner.py')
+
+copier = executable('copier', 'filecopier.c', native: true)
+
+cg = generator(runner,
+    output: ['@BASENAME@.c'],
+    arguments: [copier.full_path(), '@INPUT@', '@OUTPUT@'],
+    depends: copier)
+
+test('generatordep',
+    executable('gd', 'prog.c', cg.process('libsrc.c.in')))

test cases/common/27 pipeline/depends/prog.c

@@ -0,0 +1,5 @@
+int func();
+
+int main(int argc, char **argv) {
+    return func() != 42;
+}

test cases/common/27 pipeline/meson.build

@@ -19,3 +19,5 @@ test('pipelined', e2)
 # This is in a subdirectory to make sure
 # we write proper subdir paths to output.
 subdir('src')
+
+subdir('depends')