Merge pull request #3814 from behlec/configure-file-output

Check if calls to configure_file write to the same output file.

5 files changed, 93 insertions, 3 deletions

diff --git a/docs/markdown/snippets/configure_file_overwrite_warning.md b/docs/markdown/snippets/configure_file_overwrite_warning.md
new file mode 100644
index 0000000..550407d
--- /dev/null
+++ b/docs/markdown/snippets/configure_file_overwrite_warning.md
@@ -0,0 +1,39 @@
+## Meson warns if two calls to configure_file() write to the same file
+
+If two calls to [`configure_file()`](#Reference-manual.md#configure_file)
+write to the same file Meson will print a `WARNING:` message during
+configuration. For example:
+```meson
+project('configure_file', 'cpp')
+
+configure_file(
+      input: 'a.in',
+      output: 'out',
+      command: ['./foo.sh']
+    )
+configure_file(
+  input: 'a.in',
+  output: 'out',
+  command: ['./foo.sh']
+)
+
+```
+
+This will output:
+
+```
+The Meson build system
+Version: 0.47.0.dev1
+Source dir: /path/to/srctree
+Build dir: /path/to/buildtree
+Build type: native build
+Project name: configure_file
+Project version: undefined
+Build machine cpu family: x86_64
+Build machine cpu: x86_64
+Configuring out with command
+WARNING: Output file out for configure_file overwritten. First time written in line 3 now in line 8
+Configuring out with command
+Build targets in project: 0
+Found ninja-1.8.2 at /usr/bin/ninja
+```
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index 2c54eae..94f7bfe 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -1868,6 +1868,7 @@ class Interpreter(InterpreterBase):
         self.global_args_frozen = False  # implies self.project_args_frozen
         self.subprojects = {}
         self.subproject_stack = []
+        self.configure_file_outputs = {}
         # Passed from the outside, only used in subprojects.
         if default_project_options:
             self.default_project_options = default_project_options.copy()
@@ -3453,8 +3454,16 @@ root and issuing %s.
             raise InterpreterException('@INPUT@ used as command argument, but no input file specified.')
         # Validate output
         output = kwargs['output']
+        ofile_rpath = os.path.join(self.subdir, output)
         if not isinstance(output, str):
             raise InterpreterException('Output file name must be a string')
+        if ofile_rpath in self.configure_file_outputs:
+            mesonbuildfile = os.path.join(self.subdir, 'meson.build')
+            current_call = "{}:{}".format(mesonbuildfile, self.current_lineno)
+            first_call = "{}:{}".format(mesonbuildfile, self.configure_file_outputs[ofile_rpath])
+            mlog.warning('Output file', mlog.bold(ofile_rpath, True), 'for configure_file() at', current_call, 'overwrites configure_file() output at', first_call)
+        else:
+            self.configure_file_outputs[ofile_rpath] = self.current_lineno
         if ifile_abs:
             values = mesonlib.get_filenames_templates_dict([ifile_abs], None)
             outputs = mesonlib.substitute_values([output], values)
diff --git a/run_unittests.py b/run_unittests.py
index f4e95a3..dd109aa 100755
--- a/run_unittests.py
+++ b/run_unittests.py
@@ -2413,6 +2413,10 @@ recommended as it is not supported on some platforms''')
         self.assertRegex(out, "WARNING:.*'FOO_BAR'.*nosubst-nocopy2.txt.in.*not present.*")
         self.assertRegex(out, "WARNING:.*'empty'.*config.h.in.*not present.*")
         self.assertRegex(out, "WARNING:.*empty configuration_data.*test.py.in")
+        # Warnings for configuration files that are overwritten.
+        self.assertRegex(out, "WARNING:.*\"double_output.txt\".*overwrites")
+        self.assertRegex(out, "WARNING:.*\"subdir.double_output2.txt\".*overwrites")
+        self.assertNotRegex(out, "WARNING:.*no_write_conflict.txt.*overwrites")
         # No warnings about empty configuration data objects passed to files with substitutions
         self.assertNotRegex(out, "WARNING:.*empty configuration_data.*nosubst-nocopy1.txt.in")
         self.assertNotRegex(out, "WARNING:.*empty configuration_data.*nosubst-nocopy2.txt.in")
diff --git a/test cases/common/16 configure file/meson.build b/test cases/common/16 configure file/meson.build
index 8c375c1..d7beeb1 100644
--- a/test cases/common/16 configure file/meson.build
+++ b/test cases/common/16 configure file/meson.build
@@ -193,15 +193,15 @@ configure_file(
   configuration : configuration_data()
 )
 
-# Test that passing an empty configuration_data() object to a file with
-# @FOO@ substitutions does not print the warning.
+# test that passing an empty configuration_data() object to a file with
+# @foo@ substitutions does not print the warning.
 configure_file(
   input: 'nosubst-nocopy2.txt.in',
   output: 'nosubst-nocopy2.txt',
   configuration : configuration_data()
 )
 
-# Test that passing a configured file object to test() works, and that passing
+# test that passing a configured file object to test() works, and that passing
 # an empty configuration_data() object to a file that leads to no substitutions
 # prints a warning (see unit tests)
 test_file = configure_file(
@@ -210,6 +210,25 @@ test_file = configure_file(
   configuration: configuration_data()
 )
 
+# Test that overwriting an existing file creates a warning.
+configure_file(
+  input: 'test.py.in',
+  output: 'double_output.txt',
+  configuration: conf
+)
+configure_file(
+  input: 'test.py.in',
+  output: 'double_output.txt',
+  configuration: conf
+)
+
+# Test that the same file name in a different subdir will not create a warning
+configure_file(
+  input: 'test.py.in',
+  output: 'no_write_conflict.txt',
+  configuration: conf
+)
+
 test('configure-file', test_file)
 
 cdata = configuration_data()
diff --git a/test cases/common/16 configure file/subdir/meson.build b/test cases/common/16 configure file/subdir/meson.build
index d802c1d..146b7b6 100644
--- a/test cases/common/16 configure file/subdir/meson.build
+++ b/test cases/common/16 configure file/subdir/meson.build
@@ -17,3 +17,22 @@ configure_file(input : '../dummy.dat',
   output : 'config2-3.h',
   command : [found_script,  '@INPUT@', '@OUTPUT@'])
 run_command(check_file, join_paths(meson.current_build_dir(), 'config2-3.h'))
+
+# Test that overwriting an existing file creates a warning.
+configure_file(
+  input: '../test.py.in',
+  output: 'double_output2.txt',
+  configuration: conf
+)
+configure_file(
+  input: '../test.py.in',
+  output: 'double_output2.txt',
+  configuration: conf
+)
+
+# Test that the same file name in a different subdir will not create a warning
+configure_file(
+  input: '../test.py.in',
+  output: 'no_write_conflict.txt',
+  configuration: conf
+)