Make Polonius report any found errors by default

README.md

@@ -34,10 +34,10 @@ slower) -- these are the exact rules described in [the
 blogpost][post]. You can also use `-a LocationInsensitive` to use a
 location insensitive analysis (faster, but may yield spurious errors).
 
-By default, `cargo run` just prints timing. If you also want to see
-the results, try `--show-tuples` (which will show errors) and maybe
-`-v` (to show more intermediate computations). You can supply `--help`
-to get more docs.
+By default, `cargo run` will print any errors found, but otherwise
+just prints timing. If you also want to see successful results, try
+`--show-tuples` and maybe `-v` (to show more intermediate computations).
+You can supply `--help` to get more docs.
 
 ### How to generate your own inputs
 

book/src/getting_started.md

@@ -19,9 +19,9 @@ slower) -- these are the exact rules described in [the
 blogpost][post]. You can also use `-a LocationInsensitive` to use a
 location insensitive analysis (faster, but may yield spurious errors).
 
-By default, `cargo run` just prints timing. If you also want to see
-the results, try `--show-tuples` (which will show errors) and maybe
-`-v` (to show more intermediate computations). You can supply `--help`
-to get more docs.
+By default, `cargo run` will print any errors found, but otherwise
+just prints timing. If you also want to see successful results, try
+`--show-tuples` and maybe `-v` (to show more intermediate computations).
+You can supply `--help` to get more docs.
 
 [post]: http://smallcultfollowing.com/babysteps/blog/2018/04/27/an-alias-based-formulation-of-the-borrow-checker/

polonius-engine/src/output/mod.rs

@@ -514,6 +514,10 @@ impl<T: FactTypes> Output<T> {
             None => Cow::Owned(BTreeMap::default()),
         }
     }
+
+    pub fn has_errors(&self) -> bool {
+        !(self.errors.is_empty() && self.move_errors.is_empty() && self.subset_errors.is_empty())
+    }
 }
 
 /// Compares errors reported by Naive implementation with the errors

src/cli.rs

@@ -22,7 +22,7 @@ const PKG_DESCRIPTION: &str = env!("CARGO_PKG_DESCRIPTION");
 #[derive(Debug)]
 pub struct Options {
     algorithm: Algorithm,
-    show_tuples: bool,
+    show_tuples: Option<bool>,
     skip_timing: bool,
     verbose: bool,
     graphviz_file: Option<String>,
@@ -81,7 +81,7 @@ pub fn main(opt: Options) -> Result<(), Error> {
                     let millis = f64::from(duration.subsec_nanos()) * 0.000_000_001_f64;
                     println!("Time: {:0.3}s", seconds + millis);
                 }
-                if opt.show_tuples {
+                if opt.show_tuples.unwrap_or_else(|| output.has_errors()) {
                     dump::dump_output(&output, &output_directory, tables)
                         .expect("Failed to write output");
                 }
@@ -131,11 +131,11 @@ USAGE:
     polonius [FLAGS] [OPTIONS] <fact_dirs>...
 
 FLAGS:
-    -h, --help           Prints help information
-        --show-tuples    Show output tuples on stdout
-        --skip-timing    Do not display timing results
-    -V, --version        Prints version information
-    -v, --verbose        Show intermediate output tuples and not just errors
+    -h, --help                Prints help information
+        --[no-]show-tuples    Show output tuples on stdout, or suppress errors
+        --skip-timing         Do not display timing results
+    -V, --version             Prints version information
+    -v, --verbose             Show intermediate output tuples and not just errors
 
 OPTIONS:
     -a <algorithm> [default: Naive]
@@ -163,7 +163,13 @@ ARGS:
     // 2) parse args
     let options = Options {
         algorithm: arg_from_str(&mut args, "-a")?.unwrap_or(Algorithm::Naive),
-        show_tuples: args.contains("--show-tuples"),
+        show_tuples: if args.contains("--show-tuples") {
+            Some(true)
+        } else if args.contains("--no-show-tuples") {
+            Some(false)
+        } else {
+            None
+        },
         skip_timing: args.contains("--skip-timing"),
         verbose: args.contains(["-v", "--verbose"]),
         graphviz_file: arg_from_str(&mut args, "--graphviz-file")?,