Consolidate onto INSTA_WORKSPACE_ROOT

Now a single place where `INSTA_WORKSPACE_ROOT` & `CARGO_MANIFEST_DIR` are checked, with priority to the former.

Fixes mitsuhiko#575

Could do with an integration test

insta/src/env.rs

@@ -127,7 +127,7 @@ pub struct ToolConfig {
 impl ToolConfig {
     /// Loads the tool config for a specific manifest.
     pub fn from_manifest_dir(manifest_dir: &str) -> Result<ToolConfig, Error> {
-        ToolConfig::from_workspace(&get_cargo_workspace(manifest_dir))
+        Self::from_workspace(&get_cargo_workspace(manifest_dir))
     }
 
     /// Loads the tool config from a cargo workspace.
@@ -416,35 +416,24 @@ pub fn get_cargo_workspace(manifest_dir: &str) -> Arc<PathBuf> {
     if let Some(rv) = workspaces.get(manifest_dir) {
         rv.clone()
     } else {
-        // If INSTA_WORKSPACE_ROOT environment variable is set, use the value
-        // as-is. This is useful for those users where the compiled in
-        // CARGO_MANIFEST_DIR points to some transient location. This can easily
-        // happen if the user builds the test in one directory but then tries to
-        // run it in another: even if sources are available in the new
-        // directory, in the past we would always go with the compiled-in value.
-        // The compiled-in directory may not even exist anymore.
-        let path = if let Ok(workspace_root) = std::env::var("INSTA_WORKSPACE_ROOT") {
-            Arc::new(PathBuf::from(workspace_root))
-        } else {
-            let output = std::process::Command::new(
-                env::var("CARGO")
-                    .ok()
-                    .unwrap_or_else(|| "cargo".to_string()),
-            )
-            .arg("metadata")
-            .arg("--format-version=1")
-            .arg("--no-deps")
-            .current_dir(manifest_dir)
-            .output()
-            .unwrap();
-            let docs = crate::content::yaml::vendored::yaml::YamlLoader::load_from_str(
-                std::str::from_utf8(&output.stdout).unwrap(),
-            )
-            .unwrap();
-            let manifest = docs.first().expect("Unable to parse cargo manifest");
-            let workspace_root = PathBuf::from(manifest["workspace_root"].as_str().unwrap());
-            Arc::new(workspace_root)
-        };
+        let output = std::process::Command::new(
+            env::var("CARGO")
+                .ok()
+                .unwrap_or_else(|| "cargo".to_string()),
+        )
+        .arg("metadata")
+        .arg("--format-version=1")
+        .arg("--no-deps")
+        .current_dir(manifest_dir)
+        .output()
+        .unwrap();
+        let docs = crate::content::yaml::vendored::yaml::YamlLoader::load_from_str(
+            std::str::from_utf8(&output.stdout).unwrap(),
+        )
+        .unwrap();
+        let manifest = docs.first().expect("Unable to parse cargo manifest");
+        let workspace_root = PathBuf::from(manifest["workspace_root"].as_str().unwrap());
+        let path = Arc::new(workspace_root);
         workspaces.insert(manifest_dir.to_string(), path.clone());
         path
     }

insta/src/macros.rs

@@ -15,6 +15,24 @@ macro_rules! _function_name {
     }};
 }
 
+// If INSTA_WORKSPACE_ROOT environment variable is set, use the value as-is.
+// This is useful where CARGO_MANIFEST_DIR at compilation points to some
+// transient location. This can easily happen when building the test in one
+// directory but running it in another.
+#[doc(hidden)]
+#[macro_export]
+macro_rules! _get_workspace_root {
+    () => {{
+        use std::env;
+
+        if let Ok(workspace_root) = env::var("INSTA_WORKSPACE_ROOT") {
+            workspace_root.to_string()
+        } else {
+            env!("CARGO_MANIFEST_DIR").to_string()
+        }
+    }};
+}
+
 /// Asserts a `Serialize` snapshot in CSV format.
 ///
 /// **Feature:** `csv` (disabled by default)
@@ -349,7 +367,7 @@ macro_rules! _assert_snapshot_base {
             $name.into(),
             #[allow(clippy::redundant_closure_call)]
             &$transform(&$value),
-            env!("CARGO_MANIFEST_DIR"),
+            &$crate::_get_workspace_root!(),
             $crate::_function_name!(),
             module_path!(),
             file!(),
@@ -487,15 +505,15 @@ macro_rules! with_settings {
 macro_rules! glob {
     ($base_path:expr, $glob:expr, $closure:expr) => {{
         use std::path::Path;
-        let base = $crate::_macro_support::get_cargo_workspace(env!("CARGO_MANIFEST_DIR"))
+        let base = $crate::_macro_support::get_cargo_workspace(&$crate::_get_workspace_root!())
             .join(Path::new(file!()).parent().unwrap())
             .join($base_path)
             .to_path_buf();
 
         // we try to canonicalize but on some platforms (eg: wasm) that might not work, so
         // we instead silently fall back.
         let base = base.canonicalize().unwrap_or_else(|_| base);
-        $crate::_macro_support::glob_exec(env!("CARGO_MANIFEST_DIR"), &base, $glob, $closure);
+        $crate::_macro_support::glob_exec(&$crate::_get_workspace_root!(), &base, $glob, $closure);
     }};
 
     ($glob:expr, $closure:expr) => {{

insta/src/runtime.rs

@@ -639,8 +639,6 @@ pub fn assert_snapshot(
         assertion_line,
     )?;
 
-    let tool_config = get_tool_config(manifest_dir);
-
     // apply filters if they are available
     #[cfg(feature = "filters")]
     let new_snapshot_value =
@@ -671,7 +669,7 @@ pub fn assert_snapshot(
         .old_snapshot
         .as_ref()
         .map(|x| {
-            if tool_config.require_full_match() {
+            if ctx.tool_config.require_full_match() {
                 x.matches_fully(&new_snapshot)
             } else {
                 x.matches(&new_snapshot)
@@ -683,7 +681,7 @@ pub fn assert_snapshot(
         ctx.cleanup_passing()?;
 
         if matches!(
-            tool_config.snapshot_update(),
+            ctx.tool_config.snapshot_update(),
             crate::env::SnapshotUpdate::Force
         ) {
             // Avoid creating new files if contents match exactly. In