fix: dfx schema should not break on invalid dfx.json (#2670)

# Description

`dfx schema` should not refuse to work when a broken dfx.json is present.

Fixes #2437, [SDK-667](https://dfinity.atlassian.net/browse/SDK-667)

# How Has This Been Tested?

Added e2e.

# Checklist:

- [x] The title of this PR complies with [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/).
- [x] I have edited the CHANGELOG accordingly.
- [ ] I have made corresponding changes to the documentation.

CHANGELOG.md

@@ -736,6 +736,10 @@ Calls made to retrieve the help output for `canister update-settings` was missin
 `WARN` and `ERROR` messages are now clearly labelled as such, and the labels are colored accordingly.
 This is now included when running `dfx canister update-settings -h`.
 
+### fix: `dfx schema` does not require valid dfx.json
+
+There is no real reason for `dfx schema` to not work when a broken dfx.json is in the current folder - this is actually a very common scenario when `dfx schema` gets used.
+
 ### fix: canister call uses candid file if canister type cannot be determined
 
 The candid file specified in the field `canisters.<canister name>.candid` of dfx.json, or if that not exists `canisters.<canister name>.remote.candid`, is now used when running `dfx canister call`, even when dfx fails to determine the canister type.

e2e/tests-dfx/schema.bash

@@ -17,3 +17,8 @@ teardown() {
     assert_command jq type out.json
     assert_eq '"object"'
 }
+
+@test "dfx schema still works with broken dfx.json" {
+    jq '.broken_key="blahblahblah"' dfx.json | sponge dfx.json
+    assert_command dfx schema
+}

src/dfx/src/commands/mod.rs

@@ -1,6 +1,7 @@
 use crate::lib::environment::Environment;
 use crate::lib::error::DfxResult;
 
+use anyhow::bail;
 use clap::Subcommand;
 
 mod beta;
@@ -84,7 +85,7 @@ pub fn exec(env: &dyn Environment, cmd: Command) -> DfxResult {
         Command::Quickstart => quickstart::exec(env),
         Command::Remote(v) => remote::exec(env, v),
         Command::Replica(v) => replica::exec(env, v),
-        Command::Schema(v) => schema::exec(env, v),
+        Command::Schema(v) => schema::exec(v),
         Command::Sns(v) => sns::exec(env, v),
         Command::Start(v) => start::exec(env, v),
         Command::Stop(v) => stop::exec(env, v),
@@ -93,3 +94,10 @@ pub fn exec(env: &dyn Environment, cmd: Command) -> DfxResult {
         Command::Wallet(v) => wallet::exec(env, v),
     }
 }
+
+pub fn exec_without_env(cmd: Command) -> DfxResult {
+    match cmd {
+        Command::Schema(v) => schema::exec(v),
+        _ => bail!("Cannot execute this command without environment."),
+    }
+}

src/dfx/src/commands/schema.rs

@@ -1,7 +1,6 @@
 use std::path::PathBuf;
 
 use crate::config::dfinity::{ConfigInterface, TopLevelConfigNetworks};
-use crate::lib::environment::Environment;
 use crate::lib::error::DfxResult;
 
 use anyhow::Context;
@@ -26,7 +25,7 @@ pub struct SchemaOpts {
     outfile: Option<PathBuf>,
 }
 
-pub fn exec(_env: &dyn Environment, opts: SchemaOpts) -> DfxResult {
+pub fn exec(opts: SchemaOpts) -> DfxResult {
     let schema = match opts.r#for {
         Some(ForFile::Networks) => schema_for!(TopLevelConfigNetworks),
         _ => schema_for!(ConfigInterface),

src/dfx/src/main.rs

@@ -201,7 +201,10 @@ fn main() {
                 Err(e) => Err(e),
             }
         }
-        Err(e) => Err(e),
+        Err(e) => match command {
+            commands::Command::Schema(_) => commands::exec_without_env(command),
+            _ => Err(e),
+        },
     };
     if let Err(err) = result {
         print_error_and_diagnosis(err, error_diagnosis);