Auto merge of #3000 - matklad:error-format, r=alexcrichton

Add --message-format flag.

Closes #2982

This adds a `--message-format` flag with values `human` or `json-v1` to commands that may trigger compilation.

After the discussion in the issue I am no longer sure that this is a way to go:

* Looks like it buys nothing compared to `RUST_FLAGS` approach: a flag is more useful on the command line, but from the tool point of view there should be no significant differences between a flag and an environmental variable.

* Looks like we really want to wrap compiler's messages into our own json to tie them to particular compilation.

src/bin/bench.rs

@@ -1,5 +1,5 @@
 use cargo::core::Workspace;
-use cargo::ops;
+use cargo::ops::{self, MessageFormat};
 use cargo::util::{CliResult, CliError, Human, Config, human};
 use cargo::util::important_paths::{find_root_manifest_for_wd};
 
@@ -16,6 +16,7 @@ pub struct Options {
     flag_verbose: u32,
     flag_quiet: Option<bool>,
     flag_color: Option<String>,
+    flag_message_format: MessageFormat,
     flag_lib: bool,
     flag_bin: Vec<String>,
     flag_example: Vec<String>,
@@ -50,6 +51,7 @@ Options:
     -v, --verbose ...            Use verbose output
     -q, --quiet                  No output printed to stdout
     --color WHEN                 Coloring: auto, always, never
+    --message-format FMT         Error format: human, json [default: human]
     --frozen                     Require Cargo.lock and cache are up to date
     --locked                     Require Cargo.lock is up to date
 
@@ -75,7 +77,6 @@ pub fn execute(options: Options, config: &Config) -> CliResult<Option<()>> {
                           &options.flag_color,
                           options.flag_frozen,
                           options.flag_locked));
-
     let ops = ops::TestOptions {
         no_run: options.flag_no_run,
         no_fail_fast: false,
@@ -96,6 +97,7 @@ pub fn execute(options: Options, config: &Config) -> CliResult<Option<()>> {
                                             &options.flag_test,
                                             &options.flag_example,
                                             &options.flag_bench),
+            message_format: options.flag_message_format,
             target_rustdoc_args: None,
             target_rustc_args: None,
         },

src/bin/build.rs

@@ -1,8 +1,7 @@
 use std::env;
 
 use cargo::core::Workspace;
-use cargo::ops::CompileOptions;
-use cargo::ops;
+use cargo::ops::{self, CompileOptions, MessageFormat};
 use cargo::util::important_paths::{find_root_manifest_for_wd};
 use cargo::util::{CliResult, Config};
 
@@ -18,6 +17,7 @@ pub struct Options {
     flag_verbose: u32,
     flag_quiet: Option<bool>,
     flag_color: Option<String>,
+    flag_message_format: MessageFormat,
     flag_release: bool,
     flag_lib: bool,
     flag_bin: Vec<String>,
@@ -52,6 +52,7 @@ Options:
     -v, --verbose ...            Use verbose output
     -q, --quiet                  No output printed to stdout
     --color WHEN                 Coloring: auto, always, never
+    --message-format FMT         Error format: human, json [default: human]
     --frozen                     Require Cargo.lock and cache are up to date
     --locked                     Require Cargo.lock is up to date
 
@@ -92,6 +93,7 @@ pub fn execute(options: Options, config: &Config) -> CliResult<Option<()>> {
                                         &options.flag_test,
                                         &options.flag_example,
                                         &options.flag_bench),
+        message_format: options.flag_message_format,
         target_rustdoc_args: None,
         target_rustc_args: None,
     };

src/bin/doc.rs

@@ -1,5 +1,5 @@
 use cargo::core::Workspace;
-use cargo::ops;
+use cargo::ops::{self, MessageFormat};
 use cargo::util::{CliResult, Config};
 use cargo::util::important_paths::{find_root_manifest_for_wd};
 
@@ -17,6 +17,7 @@ pub struct Options {
     flag_verbose: u32,
     flag_quiet: Option<bool>,
     flag_color: Option<String>,
+    flag_message_format: MessageFormat,
     flag_package: Vec<String>,
     flag_lib: bool,
     flag_bin: Vec<String>,
@@ -47,6 +48,7 @@ Options:
     -v, --verbose ...            Use verbose output
     -q, --quiet                  No output printed to stdout
     --color WHEN                 Coloring: auto, always, never
+    --message-format FMT         Error format: human, json [default: human]
     --frozen                     Require Cargo.lock and cache are up to date
     --locked                     Require Cargo.lock is up to date
 
@@ -85,6 +87,7 @@ pub fn execute(options: Options, config: &Config) -> CliResult<Option<()>> {
                                             &empty,
                                             &empty,
                                             &empty),
+            message_format: options.flag_message_format,
             release: options.flag_release,
             mode: ops::CompileMode::Doc {
                 deps: !options.flag_no_deps,

src/bin/install.rs

@@ -114,6 +114,7 @@ pub fn execute(options: Options, config: &Config) -> CliResult<Option<()>> {
         release: !options.flag_debug,
         filter: ops::CompileFilter::new(false, &options.flag_bin, &[],
                                         &options.flag_example, &[]),
+        message_format: ops::MessageFormat::Human,
         target_rustc_args: None,
         target_rustdoc_args: None,
     };

src/bin/run.rs

@@ -1,5 +1,5 @@
 use cargo::core::Workspace;
-use cargo::ops;
+use cargo::ops::{self, MessageFormat};
 use cargo::util::{CliResult, CliError, Config, Human};
 use cargo::util::important_paths::{find_root_manifest_for_wd};
 
@@ -16,6 +16,7 @@ pub struct Options {
     flag_verbose: u32,
     flag_quiet: Option<bool>,
     flag_color: Option<String>,
+    flag_message_format: MessageFormat,
     flag_release: bool,
     flag_frozen: bool,
     flag_locked: bool,
@@ -42,6 +43,7 @@ Options:
     -v, --verbose ...       Use verbose output
     -q, --quiet             No output printed to stdout
     --color WHEN            Coloring: auto, always, never
+    --message-format FMT    Error format: human, json [default: human]
     --frozen                Require Cargo.lock and cache are up to date
     --locked                Require Cargo.lock is up to date
 
@@ -91,6 +93,7 @@ pub fn execute(options: Options, config: &Config) -> CliResult<Option<()>> {
                 bins: &bins, examples: &examples,
             }
         },
+        message_format: options.flag_message_format,
         target_rustdoc_args: None,
         target_rustc_args: None,
     };

src/bin/rustc.rs

@@ -1,8 +1,7 @@
 use std::env;
 
 use cargo::core::Workspace;
-use cargo::ops::{CompileOptions, CompileMode};
-use cargo::ops;
+use cargo::ops::{self, CompileOptions, CompileMode, MessageFormat};
 use cargo::util::important_paths::{find_root_manifest_for_wd};
 use cargo::util::{CliResult, CliError, Config, human};
 
@@ -19,6 +18,7 @@ pub struct Options {
     flag_verbose: u32,
     flag_quiet: Option<bool>,
     flag_color: Option<String>,
+    flag_message_format: MessageFormat,
     flag_release: bool,
     flag_lib: bool,
     flag_bin: Vec<String>,
@@ -55,6 +55,7 @@ Options:
     -v, --verbose ...        Use verbose output
     -q, --quiet              No output printed to stdout
     --color WHEN             Coloring: auto, always, never
+    --message-format FMT     Error format: human, json [default: human]
     --frozen                 Require Cargo.lock and cache are up to date
     --locked                 Require Cargo.lock is up to date
 
@@ -110,6 +111,7 @@ pub fn execute(options: Options, config: &Config) -> CliResult<Option<()>> {
                                         &options.flag_test,
                                         &options.flag_example,
                                         &options.flag_bench),
+        message_format: options.flag_message_format,
         target_rustdoc_args: None,
         target_rustc_args: options.arg_opts.as_ref().map(|a| &a[..]),
     };

src/bin/rustdoc.rs

@@ -1,5 +1,5 @@
 use cargo::core::Workspace;
-use cargo::ops;
+use cargo::ops::{self, MessageFormat};
 use cargo::util::{CliResult, Config};
 use cargo::util::important_paths::{find_root_manifest_for_wd};
 
@@ -17,6 +17,7 @@ pub struct Options {
     flag_release: bool,
     flag_quiet: Option<bool>,
     flag_color: Option<String>,
+    flag_message_format: MessageFormat,
     flag_package: Option<String>,
     flag_lib: bool,
     flag_bin: Vec<String>,
@@ -52,6 +53,7 @@ Options:
     -v, --verbose ...        Use verbose output
     -q, --quiet              No output printed to stdout
     --color WHEN             Coloring: auto, always, never
+    --message-format FMT     Error format: human, json [default: human]
     --frozen                 Require Cargo.lock and cache are up to date
     --locked                 Require Cargo.lock is up to date
 
@@ -95,6 +97,7 @@ pub fn execute(options: Options, config: &Config) -> CliResult<Option<()>> {
                                             &options.flag_test,
                                             &options.flag_example,
                                             &options.flag_bench),
+            message_format: options.flag_message_format,
             mode: ops::CompileMode::Doc { deps: false },
             target_rustdoc_args: Some(&options.arg_opts),
             target_rustc_args: None,

src/bin/test.rs

@@ -1,5 +1,5 @@
 use cargo::core::Workspace;
-use cargo::ops;
+use cargo::ops::{self, MessageFormat};
 use cargo::util::{CliResult, CliError, Human, human, Config};
 use cargo::util::important_paths::{find_root_manifest_for_wd};
 
@@ -23,6 +23,7 @@ pub struct Options {
     flag_verbose: u32,
     flag_quiet: Option<bool>,
     flag_color: Option<String>,
+    flag_message_format: MessageFormat,
     flag_release: bool,
     flag_no_fail_fast: bool,
     flag_frozen: bool,
@@ -55,6 +56,7 @@ Options:
     -v, --verbose ...            Use verbose output
     -q, --quiet                  No output printed to stdout
     --color WHEN                 Coloring: auto, always, never
+    --message-format FMT         Error format: human, json [default: human]
     --no-fail-fast               Run all tests regardless of failure
     --frozen                     Require Cargo.lock and cache are up to date
     --locked                     Require Cargo.lock is up to date
@@ -92,6 +94,7 @@ pub fn execute(options: Options, config: &Config) -> CliResult<Option<()>> {
                           &options.flag_color,
                           options.flag_frozen,
                           options.flag_locked));
+
     let root = try!(find_root_manifest_for_wd(options.flag_manifest_path, config.cwd()));
 
     let empty = Vec::new();
@@ -124,6 +127,7 @@ pub fn execute(options: Options, config: &Config) -> CliResult<Option<()>> {
             release: options.flag_release,
             mode: mode,
             filter: filter,
+            message_format: options.flag_message_format,
             target_rustdoc_args: None,
             target_rustc_args: None,
         },

src/cargo/lib.rs

@@ -211,8 +211,7 @@ pub fn version() -> String {
     })
 }
 
-fn flags_from_args<T>(usage: &str, args: &[String],
-                          options_first: bool) -> CliResult<T>
+fn flags_from_args<T>(usage: &str, args: &[String], options_first: bool) -> CliResult<T>
     where T: Decodable
 {
     let docopt = Docopt::new(usage).unwrap()

src/cargo/ops/cargo_compile.rs

@@ -59,6 +59,8 @@ pub struct CompileOptions<'a> {
     pub release: bool,
     /// Mode for this compile.
     pub mode: CompileMode,
+    /// `--error_format` flag for the compiler.
+    pub message_format: MessageFormat,
     /// Extra arguments to be passed to rustdoc (for main crate and dependencies)
     pub target_rustdoc_args: Option<&'a [String]>,
     /// The specified target will be compiled with all the available arguments,
@@ -74,6 +76,12 @@ pub enum CompileMode {
     Doc { deps: bool },
 }
 
+#[derive(Clone, Copy, PartialEq, Eq, RustcDecodable)]
+pub enum MessageFormat {
+    Human,
+    Json
+}
+
 pub enum CompileFilter<'a> {
     Everything,
     Only {
@@ -150,7 +158,7 @@ pub fn compile_ws<'a>(ws: &Workspace<'a>,
     let root_package = try!(ws.current());
     let CompileOptions { config, jobs, target, spec, features,
                          all_features, no_default_features,
-                         release, mode,
+                         release, mode, message_format,
                          ref filter, ref exec_engine,
                          ref target_rustdoc_args,
                          ref target_rustc_args } = *options;
@@ -242,6 +250,7 @@ pub fn compile_ws<'a>(ws: &Workspace<'a>,
         build_config.exec_engine = exec_engine.clone();
         build_config.release = release;
         build_config.test = mode == CompileMode::Test;
+        build_config.json_errors = message_format == MessageFormat::Json;
         if let CompileMode::Doc { deps } = mode {
             build_config.doc_all = deps;
         }

src/cargo/ops/cargo_package.rs

@@ -295,6 +295,7 @@ fn run_verify(ws: &Workspace, tar: &File, opts: &PackageOpts) -> CargoResult<()>
         filter: ops::CompileFilter::Everything,
         exec_engine: None,
         release: false,
+        message_format: ops::MessageFormat::Human,
         mode: ops::CompileMode::Build,
         target_rustdoc_args: None,
         target_rustc_args: None,

src/cargo/ops/cargo_rustc/custom_build.rs

@@ -206,8 +206,8 @@ fn build_work<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>)
         state.running(&p);
         let cmd = p.into_process_builder();
         let output = try!(cmd.exec_with_streaming(
-            &mut |out_line| state.stdout(out_line),
-            &mut |err_line| state.stderr(err_line),
+            &mut |out_line| { state.stdout(out_line); Ok(()) },
+            &mut |err_line| { state.stderr(err_line); Ok(()) },
         ).map_err(|mut e| {
             e.desc = format!("failed to run custom build command for `{}`\n{}",
                              pkg_name, e.desc);

src/cargo/ops/cargo_rustc/mod.rs

@@ -5,10 +5,12 @@ use std::fs;
 use std::path::{self, PathBuf};
 use std::sync::Arc;
 
+use rustc_serialize::json;
+
 use core::{Package, PackageId, PackageSet, Target, Resolve};
 use core::{Profile, Profiles, Workspace};
 use core::shell::ColorConfig;
-use util::{self, CargoResult, human};
+use util::{self, CargoResult, human, machine_message};
 use util::{Config, internal, ChainError, profile, join_paths, short_hash};
 
 use self::job::{Job, Work};
@@ -44,6 +46,7 @@ pub struct BuildConfig {
     pub release: bool,
     pub test: bool,
     pub doc_all: bool,
+    pub json_errors: bool,
 }
 
 #[derive(Clone, Default)]
@@ -213,7 +216,6 @@ fn rustc(cx: &mut Context, unit: &Unit) -> CargoResult<Work> {
         }
     }
     let has_custom_args = unit.profile.rustc_args.is_some();
-    let exec_engine = cx.exec_engine.clone();
 
     let filenames = try!(cx.target_filenames(unit));
     let root = cx.out_dir(unit);
@@ -241,7 +243,9 @@ fn rustc(cx: &mut Context, unit: &Unit) -> CargoResult<Work> {
     let cwd = cx.config.cwd().to_path_buf();
 
     rustc.args(&try!(cx.rustflags_args(unit)));
-
+    let json_errors = cx.build_config.json_errors;
+    let package_id = unit.pkg.package_id().clone();
+    let target = unit.target.clone();
     return Ok(Work::new(move |state| {
         // Only at runtime have we discovered what the extra -L and -l
         // arguments are for native libraries, so we process those here. We
@@ -267,7 +271,31 @@ fn rustc(cx: &mut Context, unit: &Unit) -> CargoResult<Work> {
         }
 
         state.running(&rustc);
-        try!(exec_engine.exec(rustc).chain_error(|| {
+        let process_builder = rustc.into_process_builder();
+        try!(if json_errors {
+            process_builder.exec_with_streaming(
+                &mut |line| if !line.is_empty() {
+                    Err(internal(&format!("compiler stdout is not empty: `{}`", line)))
+                } else {
+                    Ok(())
+                },
+                &mut |line| {
+                    let compiler_message = try!(json::Json::from_str(line).map_err(|_| {
+                        internal(&format!("compiler produced invalid json: `{}`", line))
+                    }));
+
+                    machine_message::FromCompiler::new(
+                        &package_id,
+                        &target,
+                        compiler_message
+                    ).emit();
+
+                    Ok(())
+                },
+            ).map(|_| ())
+        } else {
+            process_builder.exec()
+        }.chain_error(|| {
             human(format!("Could not compile `{}`.", name))
         }));
 
@@ -496,6 +524,10 @@ fn build_base_args(cx: &Context,
         cmd.arg("--color").arg(&color_config.to_string());
     }
 
+    if cx.build_config.json_errors {
+        cmd.arg("--error-format").arg("json");
+    }
+
     cmd.arg("--crate-name").arg(&unit.target.crate_name());
 
     if !test {