Auto merge of #6175 - alexheretic:compile_package_errors, r=alexcrichton

Add PackageError wrappers for activation errors

Similarly to #6157 this wraps compile errors with `PackageId` info to allow lib users, in this case rls, to discern where something went wrong.

In particular if a dependency has a dodgy version or doesn't exist the error chain will now contain a <s>PackageError that provides the package id</s> `ResolveError` that provides the package path from error-parent -> root. From this I figure out if the error better relates to a workspace member, and target that manifest for diagnostics.

src/cargo/core/resolver/errors.rs

@@ -0,0 +1,269 @@
+use std::collections::HashMap;
+use std::fmt;
+
+use core::{Dependency, PackageId, Registry, Summary};
+use failure::{Error, Fail};
+use semver;
+use util::config::Config;
+use util::lev_distance::lev_distance;
+
+use super::context::Context;
+use super::types::{Candidate, ConflictReason};
+
+/// Error during resolution providing a path of `PackageId`s.
+pub struct ResolveError {
+    cause: Error,
+    package_path: Vec<PackageId>,
+}
+
+impl ResolveError {
+    pub fn new<E: Into<Error>>(cause: E, package_path: Vec<PackageId>) -> Self {
+        Self {
+            cause: cause.into(),
+            package_path,
+        }
+    }
+
+    /// Returns a path of packages from the package whose requirements could not be resolved up to
+    /// the root.
+    pub fn package_path(&self) -> &[PackageId] {
+        &self.package_path
+    }
+}
+
+impl Fail for ResolveError {
+    fn cause(&self) -> Option<&Fail> {
+        self.cause.as_fail().cause()
+    }
+}
+
+impl fmt::Debug for ResolveError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.cause.fmt(f)
+    }
+}
+
+impl fmt::Display for ResolveError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.cause.fmt(f)
+    }
+}
+
+pub(super) fn activation_error(
+    cx: &Context,
+    registry: &mut Registry,
+    parent: &Summary,
+    dep: &Dependency,
+    conflicting_activations: &HashMap<PackageId, ConflictReason>,
+    candidates: &[Candidate],
+    config: Option<&Config>,
+) -> ResolveError {
+    let graph = cx.graph();
+    let to_resolve_err = |err| {
+        ResolveError::new(
+            err,
+            graph
+                .path_to_top(parent.package_id())
+                .into_iter()
+                .cloned()
+                .collect(),
+        )
+    };
+
+    if !candidates.is_empty() {
+        let mut msg = format!("failed to select a version for `{}`.", dep.package_name());
+        msg.push_str("\n    ... required by ");
+        msg.push_str(&describe_path(&graph.path_to_top(parent.package_id())));
+
+        msg.push_str("\nversions that meet the requirements `");
+        msg.push_str(&dep.version_req().to_string());
+        msg.push_str("` are: ");
+        msg.push_str(
+            &candidates
+                .iter()
+                .map(|v| v.summary.version())
+                .map(|v| v.to_string())
+                .collect::<Vec<_>>()
+                .join(", "),
+        );
+
+        let mut conflicting_activations: Vec<_> = conflicting_activations.iter().collect();
+        conflicting_activations.sort_unstable();
+        let (links_errors, mut other_errors): (Vec<_>, Vec<_>) = conflicting_activations
+            .drain(..)
+            .rev()
+            .partition(|&(_, r)| r.is_links());
+
+        for &(p, r) in links_errors.iter() {
+            if let ConflictReason::Links(ref link) = *r {
+                msg.push_str("\n\nthe package `");
+                msg.push_str(&*dep.package_name());
+                msg.push_str("` links to the native library `");
+                msg.push_str(link);
+                msg.push_str("`, but it conflicts with a previous package which links to `");
+                msg.push_str(link);
+                msg.push_str("` as well:\n");
+            }
+            msg.push_str(&describe_path(&graph.path_to_top(p)));
+        }
+
+        let (features_errors, other_errors): (Vec<_>, Vec<_>) = other_errors
+            .drain(..)
+            .partition(|&(_, r)| r.is_missing_features());
+
+        for &(p, r) in features_errors.iter() {
+            if let ConflictReason::MissingFeatures(ref features) = *r {
+                msg.push_str("\n\nthe package `");
+                msg.push_str(&*p.name());
+                msg.push_str("` depends on `");
+                msg.push_str(&*dep.package_name());
+                msg.push_str("`, with features: `");
+                msg.push_str(features);
+                msg.push_str("` but `");
+                msg.push_str(&*dep.package_name());
+                msg.push_str("` does not have these features.\n");
+            }
+            // p == parent so the full path is redundant.
+        }
+
+        if !other_errors.is_empty() {
+            msg.push_str(
+                "\n\nall possible versions conflict with \
+                 previously selected packages.",
+            );
+        }
+
+        for &(p, _) in other_errors.iter() {
+            msg.push_str("\n\n  previously selected ");
+            msg.push_str(&describe_path(&graph.path_to_top(p)));
+        }
+
+        msg.push_str("\n\nfailed to select a version for `");
+        msg.push_str(&*dep.package_name());
+        msg.push_str("` which could resolve this conflict");
+
+        return to_resolve_err(format_err!("{}", msg));
+    }
+
+    // We didn't actually find any candidates, so we need to
+    // give an error message that nothing was found.
+    //
+    // Maybe the user mistyped the ver_req? Like `dep="2"` when `dep="0.2"`
+    // was meant. So we re-query the registry with `deb="*"` so we can
+    // list a few versions that were actually found.
+    let all_req = semver::VersionReq::parse("*").unwrap();
+    let mut new_dep = dep.clone();
+    new_dep.set_version_req(all_req);
+    let mut candidates = match registry.query_vec(&new_dep, false) {
+        Ok(candidates) => candidates,
+        Err(e) => return to_resolve_err(e),
+    };
+    candidates.sort_unstable_by(|a, b| b.version().cmp(a.version()));
+
+    let mut msg = if !candidates.is_empty() {
+        let versions = {
+            let mut versions = candidates
+                .iter()
+                .take(3)
+                .map(|cand| cand.version().to_string())
+                .collect::<Vec<_>>();
+
+            if candidates.len() > 3 {
+                versions.push("...".into());
+            }
+
+            versions.join(", ")
+        };
+
+        let mut msg = format!(
+            "failed to select a version for the requirement `{} = \"{}\"`\n  \
+             candidate versions found which didn't match: {}\n  \
+             location searched: {}\n",
+            dep.package_name(),
+            dep.version_req(),
+            versions,
+            registry.describe_source(dep.source_id()),
+        );
+        msg.push_str("required by ");
+        msg.push_str(&describe_path(&graph.path_to_top(parent.package_id())));
+
+        // If we have a path dependency with a locked version, then this may
+        // indicate that we updated a sub-package and forgot to run `cargo
+        // update`. In this case try to print a helpful error!
+        if dep.source_id().is_path() && dep.version_req().to_string().starts_with('=') {
+            msg.push_str(
+                "\nconsider running `cargo update` to update \
+                 a path dependency's locked version",
+            );
+        }
+
+        if registry.is_replaced(dep.source_id()) {
+            msg.push_str("\nperhaps a crate was updated and forgotten to be re-vendored?");
+        }
+
+        msg
+    } else {
+        // Maybe the user mistyped the name? Like `dep-thing` when `Dep_Thing`
+        // was meant. So we try asking the registry for a `fuzzy` search for suggestions.
+        let mut candidates = Vec::new();
+        if let Err(e) = registry.query(&new_dep, &mut |s| candidates.push(s.name()), true) {
+            return to_resolve_err(e);
+        };
+        candidates.sort_unstable();
+        candidates.dedup();
+        let mut candidates: Vec<_> = candidates
+            .iter()
+            .map(|n| (lev_distance(&*new_dep.package_name(), &*n), n))
+            .filter(|&(d, _)| d < 4)
+            .collect();
+        candidates.sort_by_key(|o| o.0);
+        let mut msg = format!(
+            "no matching package named `{}` found\n\
+             location searched: {}\n",
+            dep.package_name(),
+            dep.source_id()
+        );
+        if !candidates.is_empty() {
+            let mut names = candidates
+                .iter()
+                .take(3)
+                .map(|c| c.1.as_str())
+                .collect::<Vec<_>>();
+
+            if candidates.len() > 3 {
+                names.push("...");
+            }
+
+            msg.push_str("did you mean: ");
+            msg.push_str(&names.join(", "));
+            msg.push_str("\n");
+        }
+        msg.push_str("required by ");
+        msg.push_str(&describe_path(&graph.path_to_top(parent.package_id())));
+
+        msg
+    };
+
+    if let Some(config) = config {
+        if config.cli_unstable().offline {
+            msg.push_str(
+                "\nAs a reminder, you're using offline mode (-Z offline) \
+                 which can sometimes cause surprising resolution failures, \
+                 if this error is too confusing you may with to retry \
+                 without the offline flag.",
+            );
+        }
+    }
+
+    to_resolve_err(format_err!("{}", msg))
+}
+
+/// Returns String representation of dependency chain for a particular `pkgid`.
+pub(super) fn describe_path(path: &[&PackageId]) -> String {
+    use std::fmt::Write;
+    let mut dep_path_desc = format!("package `{}`", path[0]);
+    for dep in path[1..].iter() {
+        write!(dep_path_desc, "\n    ... which is depended on by `{}`", dep).unwrap();
+    }
+    dep_path_desc
+}