New handler to set mtime embedded in pyc file to 0

README.md

@@ -87,6 +87,20 @@ and cleans up unused "flag references".
 It is a Rust reimplementation of
 the [MarshalParser Python module](https://github.com/fedora-python/marshalparser).
 
+### `pyc-zero-mtime`
+
+Accepts `*.pyc`.
+
+This handler sets the internal timestamp in `.pyc` file header to 0,
+and sets the mtime on the corresponding source `.py` file to 0.
+This is intended to be used on [OSTree](https://github.com/ostreedev/ostree)
+systems where mtimes are discarded,
+causing a mismatch between the timestamp embedded in the `.pyc` file
+and the filesystem metadata of the `.py` file.
+
+This handler is not enabled by default and must be explicitly requested
+via `--handlers pyc-zero-mtime`.
+
 ## Notes
 
 This project is inspired by

src/handlers/mod.rs

@@ -176,23 +176,24 @@ impl Stats {
 
 pub type HandlerBoxed = fn(&Rc<options::Config>) -> Box<dyn Processor>;
 
-pub const HANDLERS: &[(&str, HandlerBoxed)] = &[
-    ("ar",      ar::Ar::boxed),
-    ("jar",     jar::Jar::boxed),
-    ("javadoc", javadoc::Javadoc::boxed),
-    ("pyc",     pyc::Pyc::boxed),
+pub const HANDLERS: &[(&str, bool, HandlerBoxed)] = &[
+    ("ar",             true,  ar::Ar::boxed           ),
+    ("jar",            true,  jar::Jar::boxed         ),
+    ("javadoc",        true,  javadoc::Javadoc::boxed ),
+    ("pyc",            true,  pyc::Pyc::boxed         ),
+    ("pyc-zero-mtime", false, pyc::PycZeroMtime::boxed),
 ];
 
 pub fn handler_names() -> Vec<&'static str> {
     HANDLERS.iter()
-        .map(|(name, _)| *name)
+        .map(|(name, _, _)| *name)
         .collect()
 }
 
 pub fn make_handlers(config: &Rc<options::Config>) -> Result<Vec<Box<dyn Processor>>> {
     let mut handlers: Vec<Box<dyn Processor>> = vec![];
 
-    for (name, func) in HANDLERS {
+    for (name, _, func) in HANDLERS {
         if config.handler_names.contains(name) {
             let mut handler = func(config);
             match handler.initialize() {

src/handlers/pyc.rs

@@ -1,17 +1,20 @@
 /* SPDX-License-Identifier: GPL-3.0-or-later */
 
-use anyhow::Result;
+use anyhow::{bail, Result};
 use log::debug;
+use std::fs::File;
+use std::io;
 use std::io::{Read, Write};
 use std::iter;
 use std::path::{Path, PathBuf};
 use std::rc::Rc;
 use std::str;
+use std::time;
 
 use itertools::Itertools;
 use num_bigint_dig::{BigInt, ToBigInt};
 
-use crate::handlers::InputOutputHelper;
+use crate::handlers::{InputOutputHelper, unwrap_os_string};
 use crate::options;
 
 const PYC_MAGIC: &[u8] = &[0x0D, 0x0A];
@@ -296,16 +299,6 @@ pub fn pyc_python_version(buf: &[u8; 4]) -> Result<((u32, u32), usize)> {
     }
 }
 
-pub struct Pyc {
-    config: Rc<options::Config>,
-}
-
-impl Pyc {
-    pub fn boxed(config: &Rc<options::Config>) -> Box<dyn super::Processor> {
-        Box::new(Self { config: config.clone() })
-    }
-}
-
 #[derive(Debug)]
 #[allow(dead_code)]   // Right now, we only use dbg! to print the object.
 enum Object {
@@ -382,14 +375,55 @@ impl PycParser {
         let mut data = Vec::from(&buf);
         input.read_to_end(&mut data)?;
 
-        Ok(PycParser {
+        if data.len() < header_length {
+            return Err(super::Error::Other(
+                format!("pyc file is too short ({} < {})", data.len(), header_length)
+            ).into());
+        }
+
+        let pyc = PycParser {
             input_path: input_path.to_path_buf(),
             version,
             data,
             read_offset: header_length,
             irefs: Vec::new(),
             flag_refs: Vec::new(),
-        })
+        };
+
+        let mtime = pyc.py_content_mtime();
+        debug!("{}: from py with mtime={} ({}), size={} bytes, {}",
+               input_path.display(),
+               mtime,
+               chrono::DateTime::from_timestamp(mtime as i64, 0).unwrap(),
+               pyc.py_content_size(),
+               match pyc.py_content_hash() {
+                   None | Some(0) => "no hash invalidation".to_string(),
+                   Some(hash) => format!("hash={hash}"),
+               }
+        );
+
+        Ok(pyc)
+    }
+
+    pub fn py_content_hash(&self) -> Option<u32> {
+        if self.version < (3, 7) { // The first version supporting PEP 552
+            None
+        } else {
+            match self._read_long_at(4) {
+                0 => None,  // Let's always map 0 to None.
+                v => Some(v),
+            }
+        }
+    }
+
+    pub fn py_content_mtime(&self) -> u32 {
+        let offset = if self.version < (3, 7) { 4 } else { 8 };
+        self._read_long_at(offset)
+    }
+
+    pub fn py_content_size(&self) -> u32 {
+        let offset = if self.version < (3, 7) { 8 } else { 12 };
+        self._read_long_at(offset)
     }
 
     fn take(&mut self, count: usize) -> Result<usize> {
@@ -530,10 +564,14 @@ impl PycParser {
         })
     }
 
+    fn _read_long_at(&self, offset: usize) -> u32 {
+        let bytes = &self.data[offset .. offset + 4];
+        u32::from_le_bytes(bytes.try_into().unwrap())
+    }
+
     fn _read_long(&mut self) -> Result<u32> {
         let offset = self.take(4)?;
-        let bytes = &self.data[offset .. offset + 4];
-        Ok(u32::from_le_bytes(bytes.try_into().unwrap()))
+        Ok(self._read_long_at(offset))
     }
 
     fn _read_long_signed(&mut self) -> Result<i32> {
@@ -652,7 +690,7 @@ impl PycParser {
         Ok(Object::Dict(dict))
     }
 
-    fn clear_unused_flag_refs(&mut self) -> Result<(bool, Vec<u8>)> {
+    fn clear_unused_flag_refs(&mut self) -> Result<bool> {
         // Sequence of flag_refs and irefs ordered by number of byte in a file
         let final_list =
             iter::zip(self.flag_refs.iter(), iter::repeat(true))
@@ -698,7 +736,36 @@ impl PycParser {
 
         debug!("{}: removed {} unused FLAG_REFs", self.input_path.display(), removed_count);
         assert_eq!(data == self.data, removed_count == 0);
-        Ok((removed_count > 0, data))
+        if removed_count > 0 {
+            self.data = data;
+        }
+
+        Ok(removed_count > 0)
+    }
+
+    fn set_zero_mtime(&mut self) -> Result<bool> {
+        // Set the embedded mtime timestamp of the source .py file to 0 in the header.
+
+        if self.py_content_mtime() == 0 {
+            return Ok(false);
+        }
+
+        let offset = if self.version < (3, 7) { 4 } else { 8 };
+        self.data[offset..offset+4].fill(0);
+        assert!(self.py_content_mtime() == 0);
+
+        Ok(true)
+    }
+}
+
+
+pub struct Pyc {
+    config: Rc<options::Config>,
+}
+
+impl Pyc {
+    pub fn boxed(config: &Rc<options::Config>) -> Box<dyn super::Processor> {
+        Box::new(Self { config: config.clone() })
     }
 }
 
@@ -721,16 +788,91 @@ impl super::Processor for Pyc {
 
         parser.read_object()?;
 
-        let (have_mod, data) = parser.clear_unused_flag_refs()?;
+        let have_mod = parser.clear_unused_flag_refs()?;
         if have_mod {
             io.open_output()?;
-            io.output.as_mut().unwrap().write_all(&data)?;
+            io.output.as_mut().unwrap().write_all(&parser.data)?;
         }
 
         io.finalize(have_mod)
     }
 }
 
+
+pub struct PycZeroMtime {
+    config: Rc<options::Config>,
+}
+
+impl PycZeroMtime {
+    pub fn boxed(config: &Rc<options::Config>) -> Box<dyn super::Processor> {
+        Box::new(Self { config: config.clone() })
+    }
+
+    fn set_zero_mtime_on_py_file(&self, input_path: &Path) -> Result<()> {
+        let input_file_name = unwrap_os_string(input_path.file_name().unwrap())?;
+        let base = input_file_name.split('.').nth(0).unwrap();
+        let py_path = input_path.with_file_name(format!("{base}.py"));
+        debug!("Looking at {}…", py_path.display());
+
+        let py_file = match File::open(&py_path) {
+            Ok(some) => some,
+            Err(e) => {
+                if e.kind() == io::ErrorKind::NotFound {
+                    debug!("{}: not found, ignoring", py_path.display());
+                    return Ok(());
+                } else {
+                    bail!("{}: cannot open: {}", py_path.display(), e);
+                }
+            }
+        };
+
+        let orig = py_file.metadata()?;
+        if !orig.file_type().is_file() {
+            debug!("{}: not a file, ignoring", py_path.display());
+        } else if orig.modified()? == time::UNIX_EPOCH {
+            debug!("{}: mtime is already 0", py_path.display());
+        } else if self.config.check {
+            debug!("{}: not touching mtime in --check mode", py_path.display());
+        } else {
+            py_file.set_modified(time::UNIX_EPOCH)?;
+            debug!("{}: mtime set to 0", py_path.display());
+        }
+
+        Ok(())
+    }
+}
+
+impl super::Processor for PycZeroMtime {
+    fn name(&self) -> &str {
+        "pyc-zero-mtime"
+    }
+
+    fn filter(&self, path: &Path) -> Result<bool> {
+        Ok(path.extension().is_some_and(|x| x == "pyc"))
+    }
+
+    fn process(&self, input_path: &Path) -> Result<super::ProcessResult> {
+        let (mut io, input) = InputOutputHelper::open(input_path, self.config.check)?;
+
+        let mut parser = PycParser::from_file(input_path, input)?;
+        let have_mod = parser.set_zero_mtime()?;
+
+        if have_mod {
+            io.open_output()?;
+            io.output.as_mut().unwrap().write_all(&parser.data)?;
+        }
+
+        let res = io.finalize(have_mod)?;
+
+        if have_mod {
+            self.set_zero_mtime_on_py_file(input_path)?;
+        }
+
+        Ok(res)
+    }
+}
+
+
 #[cfg(test)]
 mod tests {
     use super::*;

src/options.rs

@@ -73,7 +73,7 @@ pub struct Config {
     pub strict_handlers: bool,
 }
 
-fn filter_by_name(name: &str, filter: &[&str]) -> bool {
+fn filter_by_name(name: &str, enabled_by_default: bool, filter: &[&str]) -> bool {
     let mut negative_filter = true;
 
     for f in filter.iter().rev() {
@@ -90,7 +90,7 @@ fn filter_by_name(name: &str, filter: &[&str]) -> bool {
         }
     }
 
-    negative_filter
+    enabled_by_default && negative_filter
 }
 
 pub fn requested_handlers(filter: &[&str]) -> Result<(Vec<&'static str>, bool)> {
@@ -109,8 +109,8 @@ pub fn requested_handlers(filter: &[&str]) -> Result<(Vec<&'static str>, bool)>
 
     let list: Vec<&'static str> = handlers::HANDLERS
         .iter()
-        .filter(|(name, _)| filter_by_name(name, filter))
-        .map(|(name, _)| *name)
+        .filter(|(name, enabled_by_default, _)| filter_by_name(name, *enabled_by_default, filter))
+        .map(|(name, _, _)| *name)
         .collect();
 
     if list.is_empty() {
@@ -213,10 +213,31 @@ mod tests {
 
     #[test]
     fn test_filter_by_name() {
-        assert_eq!(filter_by_name("x", &vec!["x", "y"]), true);
-        assert_eq!(filter_by_name("x", &vec!["x"]), true);
-        assert_eq!(filter_by_name("x", &vec![]), true);
-        assert_eq!(filter_by_name("x", &vec!["-x"]), false);
-        assert_eq!(filter_by_name("x", &vec!["-y"]), true);
+        assert_eq!(filter_by_name("x", true, &vec!["x", "y"]), true);
+        assert_eq!(filter_by_name("x", true, &vec!["x"]), true);
+        assert_eq!(filter_by_name("x", true, &vec![]), true);
+        assert_eq!(filter_by_name("x", true, &vec!["-x"]), false);
+        assert_eq!(filter_by_name("x", true, &vec!["-y"]), true);
+
+        assert_eq!(filter_by_name("x", false, &vec!["x", "y"]), true);
+        assert_eq!(filter_by_name("x", false, &vec!["x"]), true);
+        assert_eq!(filter_by_name("x", false, &vec![]), false);
+        assert_eq!(filter_by_name("x", false, &vec!["-x"]), false);
+        assert_eq!(filter_by_name("x", false, &vec!["-y"]), false);
+    }
+
+    #[test]
+    fn test_requested_handlers() {
+        let (list, strict) = requested_handlers(&vec![]).unwrap();
+        assert_eq!(list, vec!["ar", "jar", "javadoc", "pyc"]);
+        assert_eq!(strict, false);
+
+        let (list, strict) = requested_handlers(&vec!["ar", "pyc-zero-mtime"]).unwrap();
+        assert_eq!(list, vec!["ar", "pyc-zero-mtime"]);
+        assert_eq!(strict, true);
+
+        let (list, strict) = requested_handlers(&vec!["-pyc-zero-mtime"]).unwrap();
+        assert_eq!(list, vec!["ar", "jar", "javadoc", "pyc"]);
+        assert_eq!(strict, true);
     }
 }

tests/test_handlers/mod.rs

@@ -1,6 +1,7 @@
 mod test_ar;
 mod test_javadoc;
 mod test_pyc;
+mod test_pyc_zero_mtime;
 
 use anyhow::Result;
 use std::fs;