[compiletest] Ignore known paths when abbreviating output

src/tools/compiletest/src/read2.rs

@@ -5,29 +5,53 @@ pub use self::imp::read2;
 use std::io;
 use std::process::{Child, Output};
 
-pub fn read2_abbreviated(mut child: Child) -> io::Result<Output> {
+pub fn read2_abbreviated(mut child: Child, exclude_from_len: &[String]) -> io::Result<Output> {
     use io::Write;
     use std::mem::replace;
 
     const HEAD_LEN: usize = 160 * 1024;
     const TAIL_LEN: usize = 256 * 1024;
+    const EXCLUDED_PLACEHOLDER_LEN: isize = 32;
 
     enum ProcOutput {
-        Full(Vec<u8>),
+        Full { bytes: Vec<u8>, excluded_len: isize },
         Abbreviated { head: Vec<u8>, skipped: usize, tail: Box<[u8]> },
     }
 
     impl ProcOutput {
-        fn extend(&mut self, data: &[u8]) {
+        fn extend(&mut self, data: &[u8], exclude_from_len: &[String]) {
             let new_self = match *self {
-                ProcOutput::Full(ref mut bytes) => {
+                ProcOutput::Full { ref mut bytes, ref mut excluded_len } => {
                     bytes.extend_from_slice(data);
+
+                    // We had problems in the past with tests failing only in some environments,
+                    // due to the length of the base path pushing the output size over the limit.
+                    //
+                    // To make those failures deterministic across all environments we ignore known
+                    // paths when calculating the string length, while still including the full
+                    // path in the output. This could result in some output being larger than the
+                    // threshold, but it's better than having nondeterministic failures.
+                    //
+                    // The compiler emitting only excluded strings is addressed by adding a
+                    // placeholder size for each excluded segment, which will eventually reach
+                    // the configured threshold.
+                    for pattern in exclude_from_len {
+                        let pattern_bytes = pattern.as_bytes();
+                        let matches = data
+                            .windows(pattern_bytes.len())
+                            .filter(|window| window == &pattern_bytes)
+                            .count();
+                        *excluded_len += matches as isize
+                            * (EXCLUDED_PLACEHOLDER_LEN - pattern_bytes.len() as isize);
+                    }
+
                     let new_len = bytes.len();
-                    if new_len <= HEAD_LEN + TAIL_LEN {
+                    if (new_len as isize + *excluded_len) as usize <= HEAD_LEN + TAIL_LEN {
                         return;
                     }
-                    let tail = bytes.split_off(new_len - TAIL_LEN).into_boxed_slice();
-                    let head = replace(bytes, Vec::new());
+
+                    let mut head = replace(bytes, Vec::new());
+                    let tail = head.split_off(new_len - TAIL_LEN).into_boxed_slice();
                     let skipped = new_len - HEAD_LEN - TAIL_LEN;
                     ProcOutput::Abbreviated { head, skipped, tail }
                 }
@@ -47,7 +71,7 @@ pub fn read2_abbreviated(mut child: Child) -> io::Result<Output> {
 
         fn into_bytes(self) -> Vec<u8> {
             match self {
-                ProcOutput::Full(bytes) => bytes,
+                ProcOutput::Full { bytes, .. } => bytes,
                 ProcOutput::Abbreviated { mut head, skipped, tail } => {
                     write!(&mut head, "\n\n<<<<<< SKIPPED {} BYTES >>>>>>\n\n", skipped).unwrap();
                     head.extend_from_slice(&tail);
@@ -57,15 +81,15 @@ pub fn read2_abbreviated(mut child: Child) -> io::Result<Output> {
         }
     }
 
-    let mut stdout = ProcOutput::Full(Vec::new());
-    let mut stderr = ProcOutput::Full(Vec::new());
+    let mut stdout = ProcOutput::Full { bytes: Vec::new(), excluded_len: 0 };
+    let mut stderr = ProcOutput::Full { bytes: Vec::new(), excluded_len: 0 };
 
     drop(child.stdin.take());
     read2(
         child.stdout.take().unwrap(),
         child.stderr.take().unwrap(),
         &mut |is_stdout, data, _| {
-            if is_stdout { &mut stdout } else { &mut stderr }.extend(data);
+            if is_stdout { &mut stdout } else { &mut stderr }.extend(data, exclude_from_len);
             data.clear();
         },
     )?;

src/tools/compiletest/src/runtest.rs

@@ -28,7 +28,7 @@ use std::hash::{Hash, Hasher};
 use std::io::prelude::*;
 use std::io::{self, BufReader};
 use std::path::{Path, PathBuf};
-use std::process::{Command, ExitStatus, Output, Stdio};
+use std::process::{Child, Command, ExitStatus, Output, Stdio};
 use std::str;
 
 use glob::glob;
@@ -1735,6 +1735,28 @@ impl<'test> TestCx<'test> {
         dylib
     }
 
+    fn read2_abbreviated(&self, child: Child) -> Output {
+        let mut exclude_from_len = Vec::new();
+        let mut add_path = |path: &Path| {
+            let path = path.display().to_string();
+            let windows = path.replace("\\", "\\\\");
+            if windows != path {
+                exclude_from_len.push(windows);
+            }
+            exclude_from_len.push(path);
+        };
+
+        // List of strings that will not be measured when determining whether the output is larger
+        // than the output truncation threshold.
+        //
+        // Note: avoid adding a subdirectory of an already excluded directory here, otherwise the
+        // same slice of text will be double counted and the truncation might not happen.
+        add_path(&self.config.src_base);
+        add_path(&self.config.build_base);
+
+        read2_abbreviated(child, &exclude_from_len).expect("failed to read output")
+    }
+
     fn compose_and_run(
         &self,
         mut command: Command,
@@ -1769,8 +1791,7 @@ impl<'test> TestCx<'test> {
             child.stdin.as_mut().unwrap().write_all(input.as_bytes()).unwrap();
         }
 
-        let Output { status, stdout, stderr } =
-            read2_abbreviated(child).expect("failed to read output");
+        let Output { status, stdout, stderr } = self.read2_abbreviated(child);
 
         let result = ProcRes {
             status,
@@ -2959,7 +2980,7 @@ impl<'test> TestCx<'test> {
             }
         }
 
-        let output = cmd.spawn().and_then(read2_abbreviated).expect("failed to spawn `make`");
+        let output = self.read2_abbreviated(cmd.spawn().expect("failed to spawn `make`"));
         if !output.status.success() {
             let res = ProcRes {
                 status: output.status,